267 results on '"Simonetta Liuti"'
Search Results
2. Novel Rosenbluth extraction framework for Compton form factors from deeply virtual exclusive experiments
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Brandon Kriesten, Simonetta Liuti, and Andrew Meyer
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Nuclear and High Energy Physics - Abstract
We use a generalization of the Rosenbluth separation method for a model independent simultaneous extraction of the Compton Form Factors H and E, from virtual Compton scattering data on an unpolarized target. A precise evaluation of H and E, enabled by the proposed method, is the first step towards pinning down the distribution of angular momentum inside the proton.
- Published
- 2023
3. Parametrization of quark and gluon generalized parton distributions in a dynamical framework
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Brandon Kriesten, Philip Velie, Emma Yeats, Fernanda Yepez Lopez, and Simonetta Liuti
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High Energy Physics - Phenomenology ,High Energy Physics - Phenomenology (hep-ph) ,High Energy Physics::Lattice ,High Energy Physics::Phenomenology ,FOS: Physical sciences ,High Energy Physics::Experiment ,Nuclear Experiment - Abstract
We present a parametrization of the chiral even generalized parton distributions, $H$, $E$, $\widetilde{H}$, $\widetilde{E}$, for the quark, antiquark and gluon, in the perturbative QCD-parton framework. Parametric analytic forms are given as a function of two equivalent sets of variables $x,\xi,t$ (symmetric frame) and $X,\zeta,t$ (asymmetric frame), at an initial scale, $Q_o^2$. In the $X>\zeta$ region a convenient and flexible form is obtained as the product of a Regge term $\propto X^{-\alpha + \alpha' t}$, describing the low $X$ behavior, times a spectator model-based functional form depending on various mass parameters; the behavior at $X, Comment: 28 pages, 19 figures
- Published
- 2022
4. Theory of deeply virtual Compton scattering off the unpolarized proton
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Brandon Kriesten and Simonetta Liuti
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High Energy Physics - Phenomenology ,High Energy Physics - Phenomenology (hep-ph) ,FOS: Physical sciences - Abstract
Using the helicity amplitudes formalism, we study deeply virtual exclusive electron photo-production off an unpolarized nucleon target, $ep \rightarrow e' p' \gamma$, through a range of kinematics both in the fixed target setting with initial electron energies of 6 GeV, 11 GeV and 24 GeV, and for an electron ion collider. We reformulate the cross section bringing to the forefront the defining features of the $ep \rightarrow e'p'\gamma$ process, where the observables are expressed as bilinear products of the independent helicity amplitudes which completely describe it in terms of the electric, magnetic and axial currents of the nucleon. %This structure is reflected in different ways in the Deeply virtual Compton scattering and Bethe-Heitler parts of the cross section. % These contributions are checked against the Fourier harmonics-based formalism which has provided so far the underlying mathematical framework to study Deeply virtual Compton scattering and related experiments. Using theoretical model calculations of the twist-two generalized parton distributions, $ H$, $E$, $\widetilde{H}$ and $\widetilde{E}$, we uncover large discrepancies between the harmonic series and our proposed framework. Most importantly, these numerical differences appear in the intermediate $Q^2$ range which represents a sweet spot for extracting generalized parton distributions from data. % We provide a framework that is ideal, on one side, to study and compare the different conventions that can be used to describe the leading order contribution to DVCS in QCD, while on the other, it facilitates a quantitative extraction of physically meaningful information from experiment through traceable and controllable approximations in the intermediate $Q^2$ region., Comment: 22 pages, 15 figures
- Published
- 2022
5. Measurement of deeply virtual Compton scattering off He4 with the CEBAF Large Acceptance Spectrometer at Jefferson Lab
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T. A. Forest, D. P. Watts, H. Egiyan, F. Sabatié, D. Bulumulla, A. Filippi, Aditya R. Khanal, M. Khandaker, G. Rosner, Andrea Bianconi, D. Payette, Jo H. S., Y. Ghandilyan, H. Voskanyan, W. Kim, R. A. Schumacher, P. Lenisa, S. Bültmann, W. J. Briscoe, E. Pasyuk, Maxime Defurne, N. Markov, B. Torayev, R. Dupre, D. G. Ireland, Carlos A. Salgado, V. Crede, B. A. Clary, M. Contalbrigo, K. Livingston, M. Battaglieri, M. J. Amaryan, B. Yale, G. Costantini, S. Stepanyan, V. P. Kubarovsky, A. Kim, R. De Vita, J. Rowley, Whitney Armstrong, Simonetta Liuti, Krishna Neupane, J. Poudel, O. Pogorelko, K. Wei, S. Fegan, P. Eugenio, Dustin Keller, R. Paremuzyan, G. Khachatryan, Volker D. Burkert, M. L. Kabir, H. Atac, T. B. Hayward, Paolo Rossi, A. S. Biselli, R. Wishart, A. Celentano, R. W. Gothe, M. Guidal, K. Hafidi, V. Mokeev, Larry Weinstein, Gerard Gilfoyle, L. Venturelli, Michael Paolone, E. L. Isupov, D. Sokhan, M. Ehrhart, M. Caudron, M. Osipenko, S. Boiarinov, I. J. D. MacGregor, F. Bossu, A. Vossen, G. Ciullo, Fatiha Benmokhtar, Y. Prok, D. S. Carman, M. Holtrop, O. Soto, N. A. Baltzell, Nikos Sparveris, X. Wei, H. Hakobyan, M. H. Wood, E. Voutier, J. Ritman, S. Diehl, N. Dashyan, A. El Alaoui, B. McKinnon, Luciano Pappalardo, M. Bondì, K. A. Griffioen, Yordanka Ilieva, C. Ayerbe Gayoso, Nicholas Zachariou, J. C. Carvajal, Y. Perrin, V. Chesnokov, L. Barion, U. Shrestha, M. Mirazita, L. Lanza, K. Hicks, W. Phelps, V. Mascagna, D. Marchand, S. Niccolai, Alessandro Rizzo, Alexander Schmidt, I. Bedlinskiy, M. Ripani, P. Chatagnon, M. Ungaro, K. Joo, V. Sergeyeva, J. Zhang, F. X. Girod, N. Tyler, C. Djalali, T. Chetry, S. Strauch, L. Elouadrhiri, S. Joosten, I. I. Strakovsky, A. Deur, D. G. Jenkins, A. Hobart, M. Leali, T. R. O'Connell, N. Pivnyuk, A. D'Angelo, L. El Fassi, S. E. Kuhn, M. Hattawy, P. L. Cole, Martin K. Mayer, A. Kripko, and Y. G. Sharabian
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Nuclear physics ,Physics ,Spectrometer ,010308 nuclear & particles physics ,0103 physical sciences ,Compton scattering ,Perturbative QCD ,010306 general physics ,01 natural sciences - Published
- 2021
6. Quark-hadron Duality And The Transition To Pqcd - Proceedings Of The First Workshop
- Author
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Simonetta Liuti, Alessandra Fantoni, Oscar A Rondon and Simonetta Liuti, Alessandra Fantoni, Oscar A Rondon
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- 2006
7. An experimental program with high duty-cycle polarized and unpolarized positron beams at Jefferson Lab
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Anthony W. Thomas, M. Battaglieri, R. De Vita, D. Marchand, Latifa Elouadrhiri, S. Habet, Hubert Spiesberger, P. Gueye, David Hamilton, Giovanni Salmè, A. Filippi, Pete Markowitz, D. Perera, G. Kalicy, M. Muhoza, N. Kalantarians, H. Atac, M. Khandaker, J. Xie, F. Sabatié, M. Mazouz, Ashot Gasparian, I.P. Fernando, V. Klimenko, T. A. Forest, D. McNulty, Z. E. Meziani, M. Boer, M. McCaughan, A. Asaturyan, J. P. Chen, V. Kozhuharov, S. Stepanyan, Simonetta Liuti, T. Patel, Alberto Accardi, M. Spata, Andrew Puckett, Andreas Metz, Salina Ali, V. Bellini, L. Barion, V. V. Berdnikov, Alexandre Camsonne, P. E. Reimer, M. Shabestari, P. Bisio, Simon Širca, T. Averett, J. Kim, Nikolaos Sparveris, M. Poelker, M. Spreafico, H. F. Ibrahim, Dipangkar Dutta, V. Bertone, Bogdan Wojtsekhowski, Ross Milner, H. Avakian, C. E. Hyde, P. M. King, Marc Vanderhaeghen, A. Somov, Yulia Furletova, Miha Mihovilovič, V. Tadevosyan, P. Sznajder, S. Migliorati, R. S. Beminiwattha, T. Chetry, M. Guidal, Olfred Hansen, T. Kutz, Z. W. Zhao, Barbara Pasquini, Eric Voutier, L. Lanza, M. J. Amaryan, J. R. M. Annand, Fatiha Benmokhtar, T. Gautam, H. Voskanyan, Richard Trotta, Ian L. Pegg, J. F. Owens, W. J. Briscoe, Jingyi Zhou, P. Valente, M. N. H. Rashad, Gordan Krnjaic, P. Lenisa, Elena Santopinto, Joseph Grames, M. Leali, S. Zhamkochyan, M. Caudron, Kai-Thomas Brinkmann, Elton Smith, L. Marsicano, Andrei Afanasev, Luciano Pappalardo, M. Carmignotto, Donal Day, L. Venturelli, Eugene Pasyuk, M. Ungaro, C. Peng, L. Causse, D. Hasell, G. Costantini, Douglas Higinbotham, N. D’Hose, J. Murphy, P. Chatagnon, R. Dupré, M. Bondì, Alexander Ilyichev, Matteo Rinaldi, P. Stoler, Brian Raue, G. N. Grauvogel, R. Santos Estrada, Kondo Gnanvo, K. Price, Q. Liu, S. Diehl, J. Nazeer, Y. G. Sharabian, X. Zheng, S. Niccolai, P. G. Blunden, J. Arrington, Riad Suleiman, J. Erler, S. Joosten, Andrea Bianconi, H.-S. Ko, P. L. Cole, Nilanga Liyanage, I. Albayrak, K. Joo, Jan C. Bernauer, F.-X. Girod, D. Gaskell, A. Kim, Juliette Mammei, A. Italiano, M. Hattawy, C. Ayerbe Gayoso, I. I. Strakovsky, M. Yurov, N. Randazzo, A. Deur, Wally Melnitchouk, H.-G. Zaunick, Michael Kohl, A. D'Angelo, E. Nardi, M. Paolone, C. Zorn, L. El Fassi, B. T. Kriesten, L. Darmé, M. Rathnayake, A. Shahinyan, Jie Zhang, Alessandro Rizzo, D. Flay, W. Xiong, H. Dutrieux, V. Sergeyeva, S. Zhang, E. R. Kinney, Hervé Moutarde, B. Dongwi, Axel Schmidt, Rolf Ent, S. Zhao, Volker D. Burkert, A. S. Tadepalli, A. S. Biselli, Tanja Horn, G. Niculescu, T. Cao, A. Celentano, P. Nadel-Turonski, Ethan Cline, J. Roche, B. Karky, M. Contalbrigo, H. Szumila-Vance, S. Fucini, O. Rondon-Aramayo, M. De Napoli, V. Mascagna, E. Fuchey, L. Cardman, G. Ciullo, Haiyan Gao, Cynthia Keppel, M. Ehrhart, A. Movsisyan, R. Novotny, A. Hobart, Sergio Scopetta, B. McKinnon, S. A. Wood, H. Mkrtchyan, M. Tiefenback, C. Munoz Camacho, Xinzhan Bai, R. Paremuzyan, B. Sawatzky, D. Sokhan, M. Suresh, Markus Diefenthaler, Z. Ye, Mauro Raggi, M. Kerver, Y. Roblin, A. Mkrtchyan, V. P. Kubarovsky, R. Capobianco, T. J. Hague, Dustin Keller, Sonny Mantry, Vladimir Khachatryan, Peter Schweitzer, Michael Wood, Maxime Defurne, Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Laboratoire de Physique des 2 Infinis Irène Joliot-Curie (IJCLab), and Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
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cross-section ,ratio ,Photon ,parton distributions ,elastic scattering ,Parton ,polarized beam ,Electron ,Leptons Accelerators ,Structure of Nucleons ,7. Clean energy ,01 natural sciences ,Dark photon ,High Energy Physics - Experiment ,High Energy Physics - Experiment (hep-ex) ,High Energy Physics - Phenomenology (hep-ph) ,Positron ,Economica ,electromagnetic form-factors ,virtual compton-scattering ,generalized ,squared 4-momentum transfers ,lepton-flavor ,violation ,electron-proton ,parity violation ,pair production ,Physics ,[PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex] ,Nuclear Experiment (nucl-ex) ,Nuclear Experiment ,Elastic scattering ,Dark sector ,JLab ,dark photon ,Settore FIS/04 ,lepton: flavor: violation ,nucleon: generalized parton distribution ,3. Good health ,High Energy Physics - Phenomenology ,Elastic and deep inelastic Scattering ,Nucleon ,Jefferson Lab ,Nuclear and High Energy Physics ,nucleon: form factor: electromagnetic ,FOS: Physical sciences ,Socio-culturale ,helium: target ,Context (language use) ,[PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex] ,Nuclear physics ,PE2_2 ,PE2_1 ,deeply virtual Compton scattering ,0103 physical sciences ,quantum chromodynamics ,010306 general physics ,PE2_3 ,activity report ,exchange: two-photon ,electroweak interaction ,010308 nuclear & particles physics ,High Energy Physics::Phenomenology ,Ambientale ,positron: beam ,[PHYS.HPHE]Physics [physics]/High Energy Physics - Phenomenology [hep-ph] ,charge: asymmetry ,Positron Beams ,Physics::Accelerator Physics ,proposal ,High Energy Physics::Experiment - Abstract
Positron beams, both polarized and unpolarized, are identified as essential ingredients for the experimental programs at the next generation of lepton accelerators. In the context of the hadronic physics program at Jefferson Lab (JLab), positron beams are complementary, even essential, tools for a precise understanding of the electromagnetic structure of nucleons and nuclei, in both the elastic and deep-inelastic regimes. For instance, elastic scattering of polarized and unpolarized electrons and positrons from the nucleon enables a model independent determination of its electromagnetic form factors. Also, the deeply-virtual scattering of polarized and unpolarized electrons and positrons allows unambiguous separation of the different contributions to the cross section of the lepto-production of photons and of lepton-pairs, enabling an accurate determination of the nucleons and nuclei generalized parton distributions, and providing an access to the gravitational form factors. Furthermore, positron beams offer the possibility of alternative tests of the Standard Model of particle physics through the search of a dark photon, the precise measurement of electroweak couplings, and the investigation of charged lepton flavor violation. This document discusses the perspectives of an experimental program with high duty-cycle positron beams at JLab., Comment: 18 pages, 7 figures This version superseeds the previous version which scientific content was decomposed into several more elaborated articles. All of these articles will be collected in the EPJ A Topical Issue about "Positron beam and physics at Jefferson Lab (e+@Jlab)"
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- 2021
8. Parton distributions and lattice-QCD calculations: Toward 3D structure
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Marco Radici, T. J. Hobbs, C.-P. Yuan, Emanuele R. Nocera, Juan Rojo, Aurore Courtoy, Simonetta Liuti, Tie-Jiun Hou, Rui Zhang, Huey-Wen Lin, Martha Constantinou, Fred Olness, Jian Liang, Keh-Fei Liu, Anatoly Radyushkin, Pavel Nadolsky, Abha Rajan, Cédric Mezrag, Tommaso Giani, Jian-Hui Zhang, Krzysztof Kutak, Markus A. Ebert, Ted C. Rogers, Jian-Wei Qiu, Gerrit Schierholz, Aleksander Kusina, Michael Engelhardt, Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay
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perturbation theory [quantum chromodynamics] ,Nuclear and High Energy Physics ,Particle physics ,generalized parton distribution ,High Energy Physics::Lattice ,Lattice field theory ,Strong interaction ,FOS: Physical sciences ,parton: distribution function ,collinear ,Context (language use) ,Parton ,Lattice QCD ,model: parton ,transverse momentum dependence ,01 natural sciences ,High Energy Physics - Phenomenology (hep-ph) ,High Energy Physics - Lattice ,Factorization ,0103 physical sciences ,quantum chromodynamics: factorization ,Transverse Momentum Dependent PDFs (TMD PDFs) ,quantum chromodynamics: perturbation theory ,010306 general physics ,Nuclear Experiment ,Global QCD fits ,Physics ,Quantum chromodynamics ,factorization [quantum chromodynamics] ,010308 nuclear & particles physics ,[PHYS.HLAT]Physics [physics]/High Energy Physics - Lattice [hep-lat] ,High Energy Physics - Lattice (hep-lat) ,High Energy Physics::Phenomenology ,lattice field theory ,Perturbative QCD ,parton [model] ,Unpolarized/polarized parton distribution functions (PDFs) ,Generalized Parton Distributions (GPD) ,High Energy Physics - Phenomenology ,[PHYS.HPHE]Physics [physics]/High Energy Physics - Phenomenology [hep-ph] ,High Energy Physics::Experiment ,hadron ,distribution function [parton] - Abstract
The strong force which binds hadrons is described by the theory of Quantum Chromodynamics (QCD). Determining the character and manifestations of QCD is one of the most important and challenging outstanding issues necessary for a comprehensive understanding of the structure of hadrons. Within the context of the QCD parton picture, the Parton Distribution Functions (PDFs) have been remarkably successful in describing a wide variety of processes. However, these PDFs have generally been confined to the description of collinear partons within the hadron. New experiments and facilities provide the opportunity to additionally explore the transverse structure of hadrons which is described by Generalized Parton Distributions (GPDs) and Transverse Momentum Dependent Parton Distribution Functions (TMD PDFs). In our previous review, we compared and contrasted the two main approaches used to determine the collinear PDFs: the first based on perturbative QCD factorization theorems, and the second based on lattice QCD calculations. In the present report, we provide an update of recent progress on the collinear PDFs, and also expand the scope to encompass the generalized PDFs (GPDs and TMD PDFs). We review the current state of the various calculations, and consider what new data might be available in the near future. We also examine how a shared effort can foster dialog between the PDF and Lattice QCD communities, and yield improvements for these generalized PDFs., 2020 PDFLattice Report, 64 pages, 34 figures
- Published
- 2021
9. Diquark correlations in hadron physics: Origin, impact and evidence
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Bogdan Wojtsekhowski, Andrew Puckett, Y. Chen, C. Mezrag, M. Ding, G. D. Cates, P. Rossi, R. W. Gothe, M. A. Bedolla, Giovanni Salmè, S. N. Syritsyn, Jorge Segovia, Chen Chen, E. Tomasi-Gustafsson, William Brooks, Makoto Takizawa, Craig D. Roberts, M. Yu. Barabanov, A. Pilloni, Elena Santopinto, Jacopo Ferretti, Simonetta Liuti, Tanja Horn, E. Cisbani, Rolf Ent, P. Wein, Gernot Eichmann, Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay
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Nuclear Theory ,High Energy Physics::Lattice ,Hadron ,hiukkasfysiikka ,01 natural sciences ,High Energy Physics - Experiment ,Broad spectrum ,High Energy Physics - Experiment (hep-ex) ,High Energy Physics - Phenomenology (hep-ph) ,Hadron physics ,[PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex] ,Nuclear Experiment (nucl-ex) ,Nuclear Experiment ,Quantum chromodynamics ,Physics ,Diquark correlations ,Baryon spectra and structure ,High Energy Physics - Lattice (hep-lat) ,symmetry breaking: chiral ,Dyson-Schwinger equations ,Diquark ,bound state ,diquark: correlation ,High Energy Physics - Phenomenology ,Quark models ,Chiral symmetry breaking ,Phenomenology (particle physics) ,Quark ,Nuclear and High Energy Physics ,Particle physics ,[PHYS.NUCL]Physics [physics]/Nuclear Theory [nucl-th] ,FOS: Physical sciences ,[PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex] ,diquark correlations ,Nuclear Theory (nucl-th) ,High Energy Physics - Lattice ,hadron physics ,0103 physical sciences ,quantum chromodynamics ,010306 general physics ,Lattice quantum chromodynamics ,kvarkit ,010308 nuclear & particles physics ,[PHYS.HLAT]Physics [physics]/High Energy Physics - Lattice [hep-lat] ,hadron spectroscopy ,High Energy Physics::Phenomenology ,form factor: electromagnetic ,[PHYS.HPHE]Physics [physics]/High Energy Physics - Phenomenology [hep-ph] ,High Energy Physics::Experiment - Abstract
The last decade has seen a marked shift in how the internal structure of hadrons is understood. Modern experimental facilities, new theoretical techniques for the continuum bound-state problem and progress with lattice-regularised QCD have provided strong indications that soft quark+quark (diquark) correlations play a crucial role in hadron physics. For example, theory indicates that the appearance of such correlations is a necessary consequence of dynamical chiral symmetry breaking, viz. a corollary of emergent hadronic mass that is responsible for almost all visible mass in the universe; experiment has uncovered signals for such correlations in the flavour-separation of the proton's electromagnetic form factors; and phenomenology suggests that diquark correlations might be critical to the formation of exotic tetra- and penta-quark hadrons. A broad spectrum of such information is evaluated herein, with a view to consolidating the facts and therefrom moving toward a coherent, unified picture of hadron structure and the role that diquark correlations might play., 113 pages, 41 figures, 8 tables
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- 2021
10. Quark spin-orbit correlations in the proton
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Michael Engelhardt, Jeremy Green, Nesreen Hasan, Taku Izubuchi, Christos Kallidonis, Stefan Krieg, Simonetta Liuti, Stefan Meinel, John Negele, Andrew Pochinsky, Abha Rajan, Giorgio Silvi, and Sergey Syritsyn
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High Energy Physics - Phenomenology ,High Energy Physics - Lattice ,High Energy Physics - Phenomenology (hep-ph) ,High Energy Physics::Lattice ,Nuclear Theory ,High Energy Physics::Phenomenology ,High Energy Physics - Lattice (hep-lat) ,FOS: Physical sciences ,High Energy Physics::Experiment ,Nuclear Experiment - Abstract
Generalized transverse momentum-dependent parton distributions (GTMDs) provide a comprehensive framework for imaging the internal structure of the proton. In particular, by encoding the simultaneous distribution of quark transverse positions and momenta, they allow one to directly access longitudinal quark orbital angular momentum, and, moreover, to correlate it with the quark helicity. The relevant GTMD is evaluated through a lattice calculation of a proton matrix element of a quark bilocal operator (the separation in which is Fourier conjugate to the quark momentum) featuring a momentum transfer (which is Fourier conjugate to the quark position), as well as the Dirac structure appropriate for capturing the quark helicity. The weighting by quark transverse position requires a derivative with respect to momentum transfer, which is obtained in unbiased fashion using a direct derivative method. The lattice calculation is performed directly at the physical pion mass, using domain wall fermions to mitigate operator mixing effects. Both the Jaffe-Manohar as well as the Ji quark spin-orbit correlations are extracted, yielding evidence for a strong quark spin-orbit coupling in the proton., Comment: 8 pages, 2 figures, to appear in the proceedings of the 38th International Symposium on Lattice Field Theory, LATTICE2021, PoS LATTICE2021, 413
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- 2021
- Full Text
- View/download PDF
11. Parton distributions and lattice QCD calculations: toward 3D structure
- Author
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Martha Constantinou, Aurore Courtoy, Ebert, Markus A., Michael Engelhardt, Tommaso Giani, Tim Hobbs, Tie-Jiun Hou, Aleksander Kusina, Krzysztof Kutak, Jian Liang, Huey-Wen Lin, Keh-Fei Liu, Simonetta Liuti, Cédric Mezrag, Pavel Nadolsky, Nocera, Emanuele R., Fred Olness, Jian-Wei Qiu, Marco Radici, Anatoly Radyushkin, Abha Rajan, Ted Rogers, Juan Rojo, Gerrit Schierholz, P Yuan, C., Jian-Hui Zhang, and Rui Zhang
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generalized parton distribution ,High Energy Physics::Lattice ,High Energy Physics::Phenomenology ,lattice field theory ,hep-lat ,parton: distribution function ,collinear ,hep-ph ,model: parton ,transverse momentum dependence ,quantum chromodynamics: factorization ,High Energy Physics::Experiment ,hadron ,quantum chromodynamics: perturbation theory ,Nuclear Experiment - Abstract
The strong force which binds hadrons is described by the theory of Quantum Chromodynamics (QCD). Determining the character and manifestations of QCD is one of the most important and challenging outstanding issues necessary for a comprehensive understanding of the structure of hadrons. Within the context of the QCD parton picture, the Parton Distribution Functions (PDFs) have been remarkably successful in describing a wide variety of processes. However, these PDFs have generally been confined to the description of collinear partons within the hadron. New experiments and facilities provide the opportunity to additionally explore the transverse structure of hadrons which is described by Generalized Parton Distributions (GPDs) and Transverse Momentum Dependent Parton Distribution Functions (TMD PDFs). In our previous review, we compared and contrasted the two main approaches used to determine the collinear PDFs: the first based on perturbative QCD factorization theorems, and the second based on lattice QCD calculations. In the present report, we provide an update of recent progress on the collinear PDFs, and also expand the scope to encompass the generalized PDFs (GPDs and TMD PDFs). We review the current state of the various calculations, and consider what new data might be available in the near future. We also examine how a shared effort can foster dialog between the PDF and Lattice QCD communities, and yield improvements for these generalized PDFs.
- Published
- 2021
- Full Text
- View/download PDF
12. Quark-Gluon-Quark Contributions to Twist Three GPDs
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Simonetta Liuti and Abha Rajan
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Quark ,Physics ,Particle physics ,Angular momentum ,Distribution (number theory) ,High Energy Physics::Lattice ,High Energy Physics::Phenomenology ,Transverse momentum ,High Energy Physics::Experiment ,Parton ,Twist ,Nuclear Experiment ,Gluon - Abstract
Twist three Generalized Parton Distributions and Generalized Transverse Momentum Distributions are central to the description of partonic orbital angular momentum. We discuss the origin of the genuine twist three contribution, described by the quark gluon quark correlator, to the twist three Generalized Parton Distribution E˜2T and how it connects to calculations of the kT2 moments of the Generalized Transverse Momentum Distribution F14.
- Published
- 2020
13. Extraction of generalized parton distribution observables from deeply virtual electron proton scattering experiments
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Brandon Kriesten, Dustin Keller, Andrew Meyer, Liliet Calero Diaz, J. Osvaldo Gonzalez-Hernandez, Simonetta Liuti, and Gary R. Goldstein
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Physics ,Angular momentum ,Particle physics ,010308 nuclear & particles physics ,Compton scattering ,Virtual particle ,FOS: Physical sciences ,Parton ,Electron ,01 natural sciences ,High Energy Physics - Phenomenology ,High Energy Physics - Phenomenology (hep-ph) ,Total angular momentum quantum number ,0103 physical sciences ,010306 general physics ,Nucleon ,Electron scattering - Abstract
We provide the general expression of the cross section for exclusive deeply virtual photon electroproduction from a spin 1/2 target using current parameterizations of the off-forward correlation function in a nucleon for different beam and target polarization configurations up to twist three accuracy. All contributions to the cross section including deeply virtual Compton scattering, the Bethe-Heitler process, and their interference, are described within a helicity amplitude based framework which is also relativistically covariant and readily applicable to both the laboratory frame and in a collider kinematic setting. Our formalism renders a clear physical interpretation of the various components of the cross section by making a connection with the known characteristic structure of the electron scattering coincidence reactions. In particular, we focus on the total angular momentum, $J_z$, and on the orbital angular momentum, $L_z$. On one side, we uncover an avenue to a precise extraction of $J_z$, given by the combination of generalized parton distributions, $H+E$, through a generalization of the Rosenbluth separation method used in elastic electron proton scattering. On the other, we single out for the first time, the twist three angular modulations of the cross section that are sensitive to $L_z$. The proposed generalized Rosenbluth technique adds an important constraint for mapping the 3D structure of the nucleon., Comment: 62 pages, 7 figures, 3 tables
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- 2020
14. Deep Learning Analysis of Deeply Virtual Exclusive Photoproduction
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Matthias Burkardt, Jake Grigsby, Joshua Hoskins, Peter Alonzi, Brandon Kriesten, and Simonetta Liuti
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Physics ,Particle physics ,Artificial neural network ,business.industry ,Deep learning ,Compton scattering ,FOS: Physical sciences ,Probability and statistics ,Observable ,Computational Physics (physics.comp-ph) ,Outcome (probability) ,High Energy Physics - Phenomenology ,Cross section (physics) ,High Energy Physics - Phenomenology (hep-ph) ,Skewness ,Physics - Data Analysis, Statistics and Probability ,Artificial intelligence ,Nuclear Experiment (nucl-ex) ,business ,Nuclear Experiment ,Physics - Computational Physics ,Data Analysis, Statistics and Probability (physics.data-an) - Abstract
We present a Machine Learning based approach to the cross section and asymmetries for deeply virtual Compton scattering from an unpolarized proton target using both an unpolarized and polarized electron beam. Machine learning methods are needed to study and eventually interpret the outcome of deeply virtual exclusive experiments since these reactions are characterized by a complex final state with a larger number of kinematic variables and observables, exponentially increasing the difficulty of quantitative analyses. Our deep neural network (FemtoNet) uncovers emergent features in the data and learns an accurate approximation of the cross section that outperforms standard baselines. FemtoNet reveals that the predictions in the unpolarized case systematically show a smaller relative median error than the polarized that can be ascribed to the presence of the Bethe Heitler process. It also suggests that the $t$ dependence can be more easily extrapolated than for the other variables, namely the skewness, $\xi$ and four-momentum transfer, $Q^2$. Our approach is fully scalable and will be capable of handling larger data sets as they are released from future experiments., Comment: 14 pages, 12 figures
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- 2020
- Full Text
- View/download PDF
15. Mapping the Energy-Momentum Tensor: From Nucleons to Stars
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Simonetta Liuti
- Subjects
High Energy Physics::Lattice ,Nuclear Theory ,High Energy Physics::Phenomenology ,High Energy Physics::Experiment ,Nuclear Experiment - Abstract
Talk from the Strong QCD from Hadron Structure Experiments Workshop 2019
- Published
- 2019
- Full Text
- View/download PDF
16. Exploring the Structure of the Bound Proton with Deeply Virtual Compton Scattering
- Author
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A. El Alaoui, Alessandro Rizzo, C. Ayerbe Gayoso, M. Khandaker, R. Paremuzyan, Nicholas Zachariou, O. Soto, Andrea Celentano, Nicholas M. Harrison, Gerard Gilfoyle, D. P. Watts, S. Fegan, D. Sokhan, V. Crede, K. Livingston, M. Garçon, Sandra K. Johnston, R. A. Montgomery, Jie Zhang, F. X. Girod, M. Battaglieri, M. Contalbrigo, G. Gavalian, E. Golovatch, S. Strauch, Aditya R. Khanal, S. Niccolai, A. Filippi, M. Ripani, R. Dupre, N A Baltzell, K. L. Giovanetti, A. D'Angelo, E. L. Isupov, G. Khachatryan, Dustin Keller, Larry Weinstein, P. Lenisa, Yordanka Ilieva, M. Defurne, N. Markov, Chaden Djalali, Michael Wood, Laura Clark, E. De Sanctis, F. Sabatié, D. Heddle, K. A. Griffioen, T. Mineeva, L. Barion, K. Hafidi, J. Poudel, Taya Chetry, C. Munoz Camacho, P. L. Cole, Iu. Skorodumina, G. Angelini, P. Rossi, T. B. Hayward, D. Protopopescu, Z. W. Zhao, B. McKinnon, F. Hauenstein, Friedrich Klein, L. Lanza, B. Torayev, A Fradi, S. Diehl, C. Salgado, V. P. Kubarovsky, D. Riser, G. Ciullo, O. Pogorelko, M. Mirazita, H. Egiyan, F. Bossu, G. Rosner, P. Eugenio, Y. Prok, D. S. Carman, L. El Fassi, E. Pasyuk, M. Taiuti, C. W. Kim, Zein-Eddine Meziani, F. Cao, M. L. Kabir, S. E. Kuhn, M. Hattawy, H. Voskanyan, A. I. Ostrovidov, D. G. Jenkins, I. J. D. MacGregor, M. Guidal, Rong Wang, N. Dashyan, D. G. Ireland, M Ehrhart, A. S. Biselli, N. Gevorgyan, R. W. Gothe, M. Holtrop, I. Bedlinskiy, Luciano Pappalardo, Martin K. Mayer, A. Deur, W. Kim, M. Khachatryan, Nikolaos Sparveris, W. K. Brooks, S. Adhikari, Y. G. Sharabian, R. De Vita, D. Marchand, H. S. Jo, X. Wei, R. A. Schumacher, S. Bültmann, T. A. Forest, S. Stepanyan, Simonetta Liuti, M. Ungaro, Y. Perrin, K. Hicks, P. Chatagnon, P. Nadel-Turonski, N. Tyler, J. A. Tan, E. Voutier, Institut de Physique Nucléaire d'Orsay (IPNO), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Institut Polytechnique de Grenoble - Grenoble Institute of Technology-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, CLAS, Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), and Université Grenoble Alpes (UGA)
- Subjects
generalized parton distribution ,Proton ,EMC effect ,Nuclear Theory ,General Physics and Astronomy ,Virtual particle ,parton: distribution function ,Parton ,Electron ,01 natural sciences ,7. Clean energy ,High Energy Physics - Experiment ,High Energy Physics - Experiment (hep-ex) ,Electromagnetic probes ,[PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex] ,Nuclear Experiment (nucl-ex) ,Form factors, Electromagnetic probes, Nuclear Structure, Deep Virtual Compton Scattering, Quark models, Electron-ion collisions, Nuclear structure & decays, Nucleon distribution ,electron: beam ,Nuclear Experiment ,Physics ,Settore FIS/04 ,Form factors ,nucleon ,matter: effect ,kinematics ,Quark models ,Nucleon ,spin: asymmetry ,accelerator ,FOS: Physical sciences ,Socio-culturale ,[PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex] ,Nuclear Structure ,Deep Virtual Compton Scattering ,Nuclear physics ,PE2_2 ,PE2_1 ,deeply virtual Compton scattering ,CLAS ,0103 physical sciences ,structure ,010306 general physics ,PE2_3 ,Electron-ion collisions ,Nuclear Physics ,Scattering ,Nuclear structure & ,Compton scattering ,Automatic Keywords ,Physics::Accelerator Physics ,High Energy Physics::Experiment ,Nucleon distribution ,spectrometer ,decays ,experimental results ,photon: virtual - Abstract
In the past two decades, deeply virtual Compton scattering of electrons has been successfully used to advance our knowledge of the partonic structure of the free proton and investigate correlations between the transverse position and the longitudinal momentum of quarks inside the nucleon. Meanwhile, the structure of bound nucleons in nuclei has been studied in inclusive deep-inelastic lepton scattering experiments off nuclear targets, showing a significant difference in longitudinal momentum distribution of quarks inside the bound nucleon, known as the EMC effect. In this work, we report the first beam spin asymmetry (BSA) measurement of exclusive deeply virtual Compton scattering (DVCS) off a proton bound in $^4$He. The data used here were accumulated using a $6$ GeV longitudinally polarized electron beam incident on a pressurized $^4$He gaseous target placed within the CLAS spectrometer in Hall-B at the Thomas Jefferson National Accelerator Facility. The azimuthal angle ($\phi$) dependence of the BSA was studied in a wide range of virtual photon and scattered proton kinematics. The $Q^2$, $x_B$, and t dependencies of the BSA on the bound proton are compared with those on the free proton. In the whole kinematical region of our measurements, the BSA on the bound proton is smaller by 20\% to 40\%, indicating possible medium modification of its partonic structure.
- Published
- 2019
17. Parton distributions and lattice QCD calculations: A community white paper
- Author
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Giuseppe Bozzi, K. F. Liu, Christopher Monahan, C.-P. Yuan, Alberto Accardi, Robert S. Thorne, Hartmut Wittig, Constantia Alexandrou, Jian-Wei Qiu, Emanuele R. Nocera, Gerrit Schierholz, Alessandro Bacchetta, Luigi Del Debbio, Sara Collins, Kostas Orginos, Fred Olness, Rajan Gupta, Tomomi Ishikawa, Amanda Cooper-Sarkar, Jeremy Green, James Zanotti, Jiunn-Wei Chen, Simonetta Liuti, Juan Rojo, Martha Constantinou, Michael Engelhardt, Huey-Wen Lin, Pavel Nadolsky, Aleksander Kusina, Werner Vogelsang, Lucian Harland-Lang, Ingo Schienbein, (Astro)-Particles Physics, Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Institut Polytechnique de Grenoble - Grenoble Institute of Technology-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Laboratoire de Physique Subatomique et de Cosmologie ( LPSC ), and Université Joseph Fourier - Grenoble 1 ( UJF ) -Institut polytechnique de Grenoble - Grenoble Institute of Technology ( Grenoble INP ) -Institut National de Physique Nucléaire et de Physique des Particules du CNRS ( IN2P3 ) -Institut Polytechnique de Grenoble - Grenoble Institute of Technology-Centre National de la Recherche Scientifique ( CNRS ) -Université Grenoble Alpes ( UGA )
- Subjects
Quark ,Nuclear and High Energy Physics ,Particle physics ,quark: distribution function ,data analysis method ,High Energy Physics::Lattice ,Lattice field theory ,hadron: spin ,FOS: Physical sciences ,parton: distribution function ,Parton ,Lattice QCD ,01 natural sciences ,hard scattering ,High Energy Physics - Lattice ,High Energy Physics - Phenomenology (hep-ph) ,benchmark ,Factorization ,0103 physical sciences ,quantum chromodynamics ,quantum chromodynamics: factorization ,ddc:530 ,010306 general physics ,Global QCD fits ,Quantum chromodynamics ,Physics ,polarization ,gluon: distribution function ,010308 nuclear & particles physics ,[PHYS.HLAT]Physics [physics]/High Energy Physics - Lattice [hep-lat] ,High Energy Physics - Lattice (hep-lat) ,High Energy Physics::Phenomenology ,lattice field theory ,[ PHYS.HLAT ] Physics [physics]/High Energy Physics - Lattice [hep-lat] ,Observable ,Gluon ,High Energy Physics - Phenomenology ,[PHYS.HPHE]Physics [physics]/High Energy Physics - Phenomenology [hep-ph] ,[ PHYS.HPHE ] Physics [physics]/High Energy Physics - Phenomenology [hep-ph] ,High Energy Physics::Experiment ,Unpolarized/polarized parton distribution functions (PDFs) - Abstract
Progress in particle and nuclear physics 100, 107 - 160 (2018). doi:10.1016/j.ppnp.2018.01.007, In the framework of quantum chromodynamics (QCD), parton distribution functions (PDFs) quantify how the momentum and spin of a hadron are divided among its quark and gluon constituents. Two main approaches exist to determine PDFs. The first approach, based on QCD factorization theorems, realizes a QCD analysis of a suitable set of hard-scattering measurements, often using a variety of hadronic observables. The second approach, based on first-principle operator definitions of PDFs, uses lattice QCD to compute directly some PDF-related quantities, such as their moments. Motivated by recent progress in both approaches, in this document we present an overview of lattice-QCD and global-analysis techniques used to determine unpolarized and polarized proton PDFs and their moments. We provide benchmark numbers to validate present and future lattice-QCD calculations and we illustrate how they could be used to reduce the PDF uncertainties in current unpolarized and polarized global analyses. This document represents a first step towards establishing a common language between the two communities, to foster dialogue and to further improve our knowledge of PDFs., Published by Elsevier, Oxford [u.a.]
- Published
- 2018
- Full Text
- View/download PDF
18. Generalized Wandzura Wilczek Relations and Orbital Angular Momentum
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Michael Engelhardt, Simonetta Liuti, and Abha Rajan
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Quark ,Physics ,Quantum chromodynamics ,Angular momentum ,High Energy Physics::Phenomenology ,FOS: Physical sciences ,Equations of motion ,Parton ,Lorentz covariance ,Helicity ,High Energy Physics - Phenomenology ,High Energy Physics - Phenomenology (hep-ph) ,Nuclear Experiment ,Nucleon ,Mathematical physics - Abstract
New Lorentz Invariance Relations (LIRs) were presented between twist-three Generalized Parton Distributions (GPDs) and transverse momentum, $k_T$, moments of twist-two Generalized Transverse Momentum-Dependent Distributions (GTMDs). By implementing both these LIRs and the QCD Equations of Motion in the quark quark correlation function, we generated a new series of Wandzura Wilczek (WW) relations in the off-forward sector. Two of these WW relations take on a particularly interesting physical meaning in that they provide a clear interpretation of the QCD structure of Orbital Angular Momentum (OAM) in the nucleon. In particular, they provide a solution to the outstanding puzzle of how OAM could be simultaneously described by twist-two GTMDs and twist-three GPDs. Additional relations were discussed, in particular, for the helicity configurations that can be detected analyzing specific spin asymmetries: one corresponding to a longitudinally polarized quark in an unpolarized proton, associated with spin-orbit correlations, and one for transverse proton polarization, as a generalization of the relation obeyed by the $g_2$ structure function; finally, we defined a relation connecting the off-forward extension of the Sivers function to an off-forward Qiu-Sterman term., 5 pages, talk presented at QCD Evolution 2017, 22-16 May 2017, Jefferson Lab, Newport News, VA-USA
- Published
- 2018
19. Quark and Gluon Spin Dependent GPDs in a Flexible Spectator Model for Deeply Virtual Lepton Scattering Processes
- Author
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Simonetta Liuti, Gary R. Goldstein, and O.J. Gonzalez-Hernandez
- Subjects
Quark ,Physics ,Particle physics ,Scattering ,Lepton ,Gluon ,Spin-½ - Published
- 2018
20. First Exclusive Measurement of Deeply Virtual Compton Scattering off He4 : Toward the 3D Tomography of Nuclei
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M. J. Amaryan, Laura Clark, C. Gleason, P. Lenisa, W. Phelps, H. Moutarde, X. Wei, K. A. Griffioen, B. S. Ishkhanov, K. L. Giovanetti, Taya Chetry, M. Hattawy, Hovanes Egiyan, Larry Weinstein, G. Ciullo, J. P. Ball, Y. Prok, D. S. Carman, P. Eugenio, E. Golovatch, S. Strauch, J. W. Price, Friedrich Klein, L. Guo, Alessandro Rizzo, C. Munoz Camacho, D. G. Ireland, E. Voutier, Latifa Elouadrhiri, R. De Vita, V. Crede, M. Taiuti, C. Djalali, Michael Paolone, A. Movsisyan, O. Cortes, E. L. Isupov, S. Niccolai, Z. W. Zhao, C. A. Meyer, H. Y. Lu, L. Lanza, Whitney Armstrong, A. I. Ostrovidov, K. Park, G. V. Fedotov, D. P. Watts, G. Rosner, R. A. Montgomery, A. Celentano, Martin K. Mayer, R. W. Gothe, K. Livingston, A. Deur, H. Jiang, Volker D. Burkert, A. S. Biselli, D. G. Jenkins, R. Paremuzyan, Sergey Kuleshov, M. Khachatryan, A. Simonyan, Y. Ghandilyan, V. I. Mokeev, D. Heddle, H. Hakobyan, M. H. Wood, R. Dupre, S. Boiarinov, L. Colaneri, Iu. Skorodumina, S. Adhikari, S. Anefalos Pereira, S. Fegan, Jie Zhang, I. Niculescu, F. Cao, E. Pasyuk, Nikolaos Sparveris, N. Markov, K. Hicks, D. Adikaram, B. Torayev, M. Guidal, G. Charles, F. X. Girod, Z. E. Meziani, Nicholas M. Harrison, Gerard Gilfoyle, I. Bedlinskiy, N. A. Baltzell, C. Hanretty, W. Kim, P. Nadel-Turonski, William Brooks, A. Filippi, G. D. Smith, M. Holtrop, Lorenzo Zana, G. Khachatryan, M. Battaglieri, G. Niculescu, E. Seder, R. G. Fersch, F. Sabatié, W. Gohn, P. Rossi, V. P. Kubarovsky, D. Sokhan, P. L. Cole, M. Khandaker, O. Pogorelko, D. Protopopescu, B. G. Ritchie, M. Bashkanov, R. A. Schumacher, M. Ungaro, S. M. Hughes, M. Garçon, N. Dashyan, A. D'Angelo, E. De Sanctis, Sylvester Joosten, B. McKinnon, M. E. McCracken, L. A. Net, L. El Fassi, C. Salgado, M. Osipenko, Dustin Keller, A. El Alaoui, N. K. Walford, Y. Perrin, T. Mineeva, Nicholas Zachariou, S. Bültmann, M. Mirazita, E. Phelps, K. P. Adhikari, T. A. Forest, K. Hafidi, N. Gevorgyan, I. J. D. MacGregor, V. Batourine, H. Avakian, S. Stepanyan, Y. G. Sharabian, S. Pisano, K. Joo, Simonetta Liuti, Avraham Klein, M. Contalbrigo, H. Voskanyan, A. Kim, W. J. Briscoe, A. Fradi, S. E. Kuhn, J. A. Fleming, Z. Akbar, and M. Ripani
- Subjects
Physics ,Particle physics ,Time projection chamber ,Photon ,Proton ,Meson ,010308 nuclear & particles physics ,Compton scattering ,General Physics and Astronomy ,Electron ,HERA ,01 natural sciences ,7. Clean energy ,Nuclear physics ,Recoil ,0103 physical sciences ,Physics::Accelerator Physics ,Nuclear Experiment ,010306 general physics - Abstract
We report on the first measurement of the beam-spin asymmetry in the exclusive process of coherent deeply virtual Compton scattering off a nucleus. The experiment uses the 6 GeV electron beam from the Continuous Electron Beam Accelerator Facility (CEBAF) accelerator at Jefferson Lab incident on a pressurized $^{4}\mathrm{He}$ gaseous target placed in front of the CEBAF Large Acceptance Spectrometer (CLAS). The scattered electron is detected by CLAS and the photon by a dedicated electromagnetic calorimeter at forward angles. To ensure the exclusivity of the process, a specially designed radial time projection chamber is used to detect the recoiling $^{4}\mathrm{He}$ nuclei. We measure beam-spin asymmetries larger than those observed on the free proton in the same kinematic domain. From these, we are able to extract, in a model-independent way, the real and imaginary parts of the only $^{4}\mathrm{He}$ Compton form factor, ${\mathcal{H}}_{A}$. This first measurement of coherent deeply virtual Compton scattering on the $^{4}\mathrm{He}$ nucleus, with a fully exclusive final state via nuclear recoil tagging, leads the way toward 3D imaging of the partonic structure of nuclei.
- Published
- 2017
21. Generalized Parton Distributions in Deeply Virtual Lepton Scattering Processes
- Author
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Gary R. Goldstein and Simonetta Liuti
- Subjects
Physics ,Quark ,Quantum chromodynamics ,Particle physics ,High Energy Physics::Lattice ,Nuclear Theory ,High Energy Physics::Phenomenology ,Parton ,Parity (physics) ,Helicity ,Gluon ,Diquark ,Pseudoscalar ,High Energy Physics::Experiment ,Nuclear Experiment - Abstract
Spin and transverse momentum dependent Generalized Parton Distributions (GPDs) exist at the interface between the non-perturbative regime of QCD hadron structure and observable quantities. The distributions appear as linear superpositions and convolutions within helicity amplitudes for parton-nucleon scattering processes, which, in turn, occur in amplitudes for leptoproduction processes. We have developed a “flexible model" of quark and gluon GPDs that incorporates diquark and other spectators, Regge behavior and evolution. Chiral even GPDs determine deeply virtual Compton scattering amplitudes and are compared with cross section and polarization data. The chiral odd GPDs can be generated from these via parity relations. Those chiral odd GPDs, including “transversity", lead to predictions for pseudoscalar leptoproduction. We will present relations between crucial quark-nucleon or gluon-nucleon GPDs and the rich array of angular distributions in Deeply Virtual Scattering processes.
- Published
- 2017
22. Lorentz Invariance and QCD Equation of Motion Relations for Generalized Parton Distributions and the Dynamical Origin of Proton Orbital Angular Momentum
- Author
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Simonetta Liuti, Abha Rajan, and Michael Engelhardt
- Subjects
Physics ,Angular momentum ,010308 nuclear & particles physics ,Equations of motion ,FOS: Physical sciences ,Parton ,Lorentz covariance ,01 natural sciences ,Helicity ,High Energy Physics - Phenomenology ,High Energy Physics - Phenomenology (hep-ph) ,Total angular momentum quantum number ,Quantum electrodynamics ,0103 physical sciences ,Angular momentum coupling ,Orbital motion ,010306 general physics ,Nuclear Experiment - Abstract
We derive new Lorentz Invariance and Equation of Motion Relations between twist-three Generalized Parton Distributions (GPDs) and moments in the parton transverse momentum, $k_T$, of twist-two Generalized Transverse Momentum-Dependent Distributions (GTMDs), as a function of the parton longitudinal momentum fraction $x$. Although GTMDs in principle define the observables for partonic orbital motion, experiments that can unambiguously detect them appear remote at present. The relations presented here provide a solution to this impasse in that, e.g., the orbital angular momentum density is connected to directly measurable twist-three GPDs. Out of 16 possible Equation of Motion relations that can be written in the T-even sector, we focus on three helicity configurations that can be detected analyzing specific spin asymmetries: two correspond to longitudinal proton polarization and are associated with quark orbital angular momentum and spin-orbit correlations; the third, obtained for transverse proton polarization, is a generalization of the relation obeyed by the $g_2$ structure function. We also exhibit an additional relation connecting the off-forward extension of the Sivers function to an off-forward Qiu-Sterman term., Comment: 37 pages, 2 figures
- Published
- 2017
- Full Text
- View/download PDF
23. Pre-Town Meeting on spin physics at an Electron-Ion Collider
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Ian Balitsky, J. Huang, Simonetta Liuti, Wally Melnitchouk, Stanley J. Brodsky, Matthias Grosse Perdekamp, Xiangdong Ji, V. P. Kubarovsky, Elke C. Aschenauer, Andrey Tarasov, Minghui Liu, Xiaodong Jiang, Zhong-Bo Kang, Charles Hyde, Anatoly Radyushkin, Leonard Gamberg, L. C. Bland, J. G. Lajoie, A. Deshpande, Marco Stratmann, Feng Yuan, Volker D. Burkert, Markus Diehl, E. P. Sichtermann, Alexei Prokudin, David G. Richards, Piet J. Mulders, K. F. Liu, Matthias Burkardt, Jian-Wei Qiu, Jian-Ping Chen, and Werner Vogelsang
- Subjects
Quark ,Nuclear and High Energy Physics ,Particle physics ,Hadron ,FOS: Physical sciences ,Electron ,Atomic ,01 natural sciences ,High Energy Physics - Experiment ,High Energy Physics - Experiment (hep-ex) ,Particle and Plasma Physics ,High Energy Physics - Phenomenology (hep-ph) ,0103 physical sciences ,Nuclear ,ddc:530 ,SDG 14 - Life Below Water ,010306 general physics ,Spin (physics) ,Nuclear Experiment ,Quantum chromodynamics ,Physics ,010308 nuclear & particles physics ,Molecular ,Nuclear & Particles Physics ,Gluon ,High Energy Physics - Phenomenology ,Orbital motion ,Physics::Accelerator Physics ,High Energy Physics::Experiment ,Nucleon - Abstract
The European physical journal / A 53(4), 71 (2017). doi:10.1140/epja/i2017-12251-4, A polarized ep/eA collider (Electron-Ion Collider, or EIC), with polarized proton and light-ion beams and unpolarized heavy-ion beams with a variable center-of-mass energy $\sqrt{s} ∼ 20 to ∼100 GeV$ (upgradable to $∼ 150 GeV$) and a luminosity up to $∼ 10^{34} cm^{-2}s^{-1}$, would be uniquely suited to address several outstanding questions of Quantum Chromodynamics, and thereby lead to new qualitative and quantitative information on the microscopic structure of hadrons and nuclei. During this meeting at Jefferson Lab we addressed recent theoretical and experimental developments in the spin and the three-dimensional structure of the nucleon (sea quark and gluon spatial distributions, orbital motion, polarization, and their correlations). This mini-review contains a short update on progress in these areas since the EIC White paper (A. Accardi et al., Eur. Phys. J. A 52, 268 (2016))., Published by Springer, Berlin
- Published
- 2017
24. Extracting Spin Dependent Parton Distributions from Deeply Virtual Scattering Processes
- Author
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Simonetta Liuti and Gary R. Goldstein
- Subjects
Physics ,Particle physics ,Scattering ,Parton ,Spin-½ - Published
- 2016
25. Extraction of αs from deep inelastic scattering at large x
- Author
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Aurore Courtoy and Simonetta Liuti
- Subjects
Quantum chromodynamics ,Physics ,Coupling constant ,Coupling ,Nuclear and High Energy Physics ,Particle physics ,Intersection ,Proton ,Quantum electrodynamics ,Duality (optimization) ,Deep inelastic scattering ,Resonance (particle physics) - Abstract
We present an analysis of the role of the running coupling constant at the intersection of perturbative and non-perturbative QCD. Although the approaches that have been considered so far in these two regimes appear to be complementary to each other, a unified description might be derived through the definition of the effective coupling, as they both provide ways of analyzing its freezing at low values of the scale. We extract the effective coupling from all available experimental data on the unpolarized structure function of the proton, F 2 p , at large values of Bjorken x, including the resonance region. We suggest that parton–hadron duality observed in this region can be explained if non-perturbative effects are included in the coupling constant. The outcome of our analysis is a smooth transition from perturbative to non-perturbative QCD physics, embodied in the running of the coupling constant at intermediate scales.
- Published
- 2013
26. GPD phenomenology and DVCS fitting
- Author
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Hervé Moutarde, Simonetta Liuti, and Krešimir Kumerički
- Subjects
Physics ,Nuclear and High Energy Physics ,Particle physics ,Relation (database) ,010308 nuclear & particles physics ,Compton scattering ,FOS: Physical sciences ,Parton ,Observable ,01 natural sciences ,Phenomenology (philosophy) ,High Energy Physics - Phenomenology ,High Energy Physics - Phenomenology (hep-ph) ,0103 physical sciences ,generalized parton distributions ,partons ,proton ,deeply virtual Compton scattering ,010306 general physics - Abstract
We review the phenomenological framework for accessing Generalized Parton Distributions (GPDs) using measurements of Deeply Virtual Compton Scattering (DVCS) from a proton target. We describe various GPD models and fitting procedures, emphasizing specific challenges posed both by the internal structure and properties of the GPD functions and by their relation to observables. Bearing in mind forthcoming data of unprecedented accuracy, we give a set of recommendations to better define the pathway for a precise extraction of GPDs from experiment., Comment: 32 pages, 10 figures, contribution to the EPJA topical issue on 3D Structure of the Nucleon
- Published
- 2016
27. Disentangling Spin Dependent GPDs Through Deeply Virtual Processes with Polarizations and Azimuthal Correlations
- Author
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Simonetta Liuti and Gary R. Goldstein
- Subjects
Quantum chromodynamics ,Physics ,Particle physics ,High Energy Physics::Phenomenology ,Hadron ,Observable ,Parton ,Polarization (waves) ,Helicity ,Azimuth ,Amplitude ,Quantum electrodynamics ,High Energy Physics::Experiment ,Nuclear Experiment - Abstract
Spin and transverse momentum dependent parton distributions - Generalized Parton Distributions (GPDs) - are at the interface between the QCD structure of the hadrons and observable quantities. The GPDs are linear superpositions within helicity amplitudes. The amplitudes are probed in high energy leptoproduction processes through angular dependent cross sections and polarization asymmetries. Phenomenological extraction of the amplitudes and the distributions is a challenging task. We present observables that connect particularly with the chiral odd quark-nucleon helicity amplitudes for Deeply Virtual p 0 Production.
- Published
- 2016
28. Orbital Angular Momentum in QCD and its Observability through Deep Inelastic Processes
- Author
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Simonetta Liuti
- Subjects
Physics ,Quantum chromodynamics ,Angular momentum ,Particle physics ,Observability - Published
- 2016
29. Towards a Direct Measurement of the Quark Orbital Angular Momentum Distribution
- Author
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Simonetta Liuti
- Subjects
Physics ,Quark ,symbols.namesake ,Angular momentum ,Fourier transform ,symbols ,Wigner distribution function ,Parton ,Gauge (firearms) ,Nuclear Experiment ,Spin (physics) ,Space (mathematics) ,Mathematical physics - Abstract
We discuss two different definitions of partonic orbital angular momentum given in the literature in terms of the Fourier transform of a Wigner distribution, F14, and a twist three generalized parton distribution, Ẽ2T , respectively. We derive a relation between the two definitions which reflects their specific spin and intrinsic transverse momentum/transverse space correlations as well as their gauge link structure.
- Published
- 2016
30. Parton Transverse Momentum and Orbital Angular Momentum Distributions
- Author
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Michael Engelhardt, Aurore Courtoy, Simonetta Liuti, and Abha Rajan
- Subjects
Physics ,Angular momentum ,Particle physics ,010308 nuclear & particles physics ,High Energy Physics::Lattice ,High Energy Physics::Phenomenology ,FOS: Physical sciences ,Position and momentum space ,01 natural sciences ,Azimuthal quantum number ,High Energy Physics - Phenomenology ,High Energy Physics - Phenomenology (hep-ph) ,Total angular momentum quantum number ,Quantum electrodynamics ,0103 physical sciences ,Angular momentum coupling ,Angular momentum of light ,Orbital angular momentum of light ,High Energy Physics::Experiment ,Angular momentum operator ,010306 general physics - Abstract
The quark orbital angular momentum component of proton spin, $L_q$, can be defined in QCD as the integral of a Wigner phase space distribution weighting the cross product of the quark's transverse position and momentum. It can also be independently defined from the operator product expansion for the off-forward Compton amplitude in terms of a twist-three generalized parton distribution. We provide an explicit link between the two definitions, connecting them through their dependence on partonic intrinsic transverse momentum. Connecting the definitions provides the key for correlating direct experimental determinations of $L_q$, and evaluations through Lattice QCD calculations. The direct observation of quark orbital angular momentum does not require transverse spin polarization, but can occur using longitudinally polarized targets., Comment: 5 pages, 2 figures
- Published
- 2016
- Full Text
- View/download PDF
31. GENERALIZED PARTON DISTRIBUTIONS IN THE CHIRAL ODD SECTOR AND THEIR ROLE IN NEUTRAL MESON ELECTROPRODUCTION
- Author
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Simonetta Liuti, Gary R. Goldstein, and J. Osvaldo Gonzalez-Hernandez
- Subjects
Physics ,Angular momentum ,Particle physics ,Meson ,C parity ,Momentum transfer ,Parton ,Parity (physics) ,Quantum number ,Helicity - Abstract
Our original suggestion to investigate exclusive π0 electroproduction as a method for extracting from data the tensor charge, transversity, and other quantities related to chiral odd generalized parton distributions is further examined. We now explain the details of the process: i) the connection between the helicity description and the cartesian basis; ii) the dependence on the momentum transfer squared, Q2, and iii) the angular momentum, parity, and charge conjugation constraints (JPC quantum numbers).
- Published
- 2012
32. RELATIONS BETWEEN TRANSVERSE MOMENTUM DISTRIBUTIONS AND CHIRAL ODD GENERALIZED PARTON DISTRIBUTIONS
- Author
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Gary R. Goldstein, Simonetta Liuti, J. Osvaldo Gonzalez Hernandez, and Kunal Kathuria
- Subjects
Physics ,Particle physics ,Proton ,Transverse momentum ,Parton ,Spin structure ,Nuclear Experiment ,Deep inelastic scattering ,Parametrization ,Connection (mathematics) ,Mathematical physics - Abstract
We discuss the information on the spin structure of the proton that one can access by studying transverse momentum distributions, generalized parton distributions and their connection through generalized transverse momentum distributions. A "flexible" parametrization is proposed to extract this information from deeply virtual exclusive experiments.
- Published
- 2012
33. Generalized parton distributions from hadronic observables: non-zero skewness
- Author
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Saeed Ahmad, Simonetta Liuti, Heli Honkanen, and Swadhin K. Taneja
- Subjects
Quantum chromodynamics ,Physics ,Particle physics ,Physics and Astronomy (miscellaneous) ,Lattice field theory ,Compton scattering ,FOS: Physical sciences ,Parton ,Observable ,Deep inelastic scattering ,High Energy Physics - Phenomenology ,High Energy Physics - Phenomenology (hep-ph) ,Skewness ,Orthogonal polynomials ,Statistical physics ,Engineering (miscellaneous) - Abstract
We propose a physically motivated parametrization for the unpolarized generalized parton distributions, H and E, valid at both zero and non-zero values of the skewness variable, \zeta. Our approach follows a previous detailed study of the \zeta=0 case where H and E were determined using constraints from simultaneous fits of the experimental data on both the nucleon elastic form factors and the deep inelastic structure functions in the non singlet sector. Additional constraints at \zeta \neq 0 are provided by lattice calculations of the higher moments of generalized parton distributions. We illustrate a method for extracting generalized parton distributions from lattice moments based on a reconstruction using sets of orthogonal polynomials. The inclusion in our fit of data on Deeply Virtual Compton Scattering is also discussed. Our method provides a step towards a model independent extraction of generalized distributions from the data. It also provides an alternative to double distributions based phenomenological models in that we are able to satisfy the polynomiality condition by construction, using a combination of experimental data and lattice, without resorting to any specific mathematical construct., Comment: 29 pages, 8 figures; added references, changed text in several places
- Published
- 2009
34. Flexible parametrization of generalized parton distributions: The chiral-odd sector
- Author
-
J. Osvaldo Gonzalez Hernandez, Gary R. Goldstein, and Simonetta Liuti
- Subjects
Physics ,Nuclear and High Energy Physics ,Particle physics ,Meson ,High Energy Physics::Lattice ,Nuclear Theory ,High Energy Physics::Phenomenology ,Parton ,Parity (physics) ,Deep inelastic scattering ,Pseudoscalar meson ,Pseudoscalar ,Diquark ,Nuclear Experiment ,Pseudovector - Abstract
We present a physically motivated parametrization of the chiral-odd generalized parton distributions. The parametrization is an extension of our previous one in the chiral-even sector which was based on the Reggeized diquark model. While for chiral-even generalized distributions a quantitative fit with uncertainty estimation can be performed using deep inelastic scattering data, nucleon electromagnetic, axial and pseudoscalar form factors measurements, and all available deeply virtual Compton scattering data, the chiral-odd sector is far less constrained. While awaiting the analysis of measurements on pseudoscalar mesons exclusive electroproduction which are key for the extraction of chiral-odd GPDs, we worked out a connection between the chiral-even and chiral-odd reduced helicity amplitudes using parity transformations. The connection works for quark-parton models including both scalar and axial vector diquark models, and spectator models in general. This relation allows us to estimate the size of the various chiral-odd contributions and it opens the way for future quantitative fits.
- Published
- 2015
35. Defining the Observables for Quarks and Gluons Orbital Angular Momentum Distributions
- Author
-
J. O. Gonzalez Hernandez, Abha Rajan, Gary R. Goldstein, Simonetta Liuti, and Aurore Courtoy
- Subjects
Physics ,Particle physics ,Angular momentum ,Total angular momentum quantum number ,High Energy Physics::Phenomenology ,Angular momentum of light ,Orbital motion ,Angular momentum coupling ,Orbital angular momentum of light ,Angular momentum operator ,Atomic and Molecular Physics, and Optics ,Azimuthal quantum number - Abstract
We present a critical discussion of the observables that have been recently put forth to describe quarks and gluons orbital angular momentum distributions. Starting from a standard parameterization of the energy momentum tensor in QCD one can single out two forms of angular momentum, a so-called kinetic term, generally associated with the Ji decomposition, and a canonical term from the Jaffe Manohar decomposition. Orbital angular momentum has been connected to a Generalized Transverse Momentum Distribution (GTMD), for the canonical term, and to a twist three Generalized Parton Distribution for the kinetic term. We argue that while the latter appears as an azymuthal angular modulation in the longitudinal target spin asymmetry in deeply virtual Compton scattering, due to parity constraints, the GTMD associated with canonical angular momentum cannot be measured in a similar set of experiments.
- Published
- 2015
36. Beyond-Standard-Model Tensor Interaction and Hadron Phenomenology
- Author
-
Simonetta Liuti, Stefan Baeßler, Martín González–Alonso, Aurore Courtoy, Institut de Physique Nucléaire de Lyon (IPNL), Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)
- Subjects
Quantum chromodynamics ,Physics ,Particle physics ,Physics beyond the Standard Model ,Hadron ,Lattice field theory ,High Energy Physics::Phenomenology ,General Physics and Astronomy ,FOS: Physical sciences ,Observable ,Parton ,Lattice QCD ,High Energy Physics - Phenomenology ,High Energy Physics - Phenomenology (hep-ph) ,[PHYS.HPHE]Physics [physics]/High Energy Physics - Phenomenology [hep-ph] ,High Energy Physics::Experiment ,Nuclear Experiment ,Phenomenology (particle physics) - Abstract
We evaluate the impact of recent developments in hadron phenomenology on extracting possible fundamental tensor interactions beyond the standard model. We show that a novel class of observables, including the chiral-odd generalized parton distributions, and the transversity parton distribution function can contribute to the constraints on this quantity. Experimental extractions of the tensor hadronic matrix elements, if sufficiently precise, will provide a so far absent testing ground for lattice QCD calculations., Comment: 5 pages, 2 figures
- Published
- 2015
- Full Text
- View/download PDF
37. Violations of parton-hadron duality in Deep Inelastic Scattering
- Author
-
Simonetta Liuti
- Subjects
Quantum chromodynamics ,Physics ,Nuclear and High Energy Physics ,Particle physics ,High Energy Physics::Phenomenology ,Duality (optimization) ,Perturbative QCD ,Parton ,Inelastic scattering ,Deep inelastic scattering ,Delta baryon ,High Energy Physics::Experiment ,Invariant mass ,Nuclear Experiment - Abstract
I present an overview of recent data on Deep Inelastic Scattering at large Bjorken x and low invariant mass, W2, where parton-hadron duality was originally observed. I discuss the concept of parton-hadron duality from the perspective of perturbative QCD. Within this framework, I show that parton-hadron duality is broken for low values of W2, in the \(\Delta\)- and S11-resonance production region. A model that accounts for the anomalous scale dependence ensuing from this situation is developed.
- Published
- 2003
38. On the observability of the quark orbital angular momentum distribution
- Author
-
Abha Rajan, J. Osvaldo Gonzalez Hernandez, Gary R. Goldstein, Aurore Courtoy, and Simonetta Liuti
- Subjects
Physics ,Particle physics ,Nuclear and High Energy Physics ,FOS: Physical sciences ,Helicity ,Azimuthal quantum number ,High Energy Physics - Phenomenology ,High Energy Physics - Phenomenology (hep-ph) ,Total angular momentum quantum number ,Quantum electrodynamics ,Angular momentum coupling ,Orbital motion ,Angular momentum of light ,Orbital angular momentum of light ,Angular momentum operator - Abstract
We argue that due to Parity constraints, the helicity combination of the purely momentum space counterparts of the Wigner distributions -- the generalized transverse momentum distributions -- that describes the configuration of an unpolarized quark in a longitudinally polarized nucleon, can enter the deeply virtual Compton scattering amplitude only through matrix elements involving a final state interaction. The relevant matrix elements in turn involve light cone operators projections in the transverse direction, or they appear in the deeply virtual Compton scattering amplitude at twist three. Orbital angular momentum or the spin structure of the nucleon was a major reason for these various distributions and amplitudes to have been introduced. We show that the twist three contributions associated to orbital angular momentum %to deeply virtual Compton scattering provide observables related to orbital angular momentum and are related to the target-spin asymmetry in deeply virtual Compton scattering, already measured at HERMES., Comment: 10 pages, 3 figures; version published in Physics Letters B
- Published
- 2014
39. Studies of QCD at the Intersection of the Perturbative and Non-Perturbative Regimes
- Author
-
Simonetta Liuti
- Published
- 2013
40. Asymptotic gluon shadowing
- Author
-
Simonetta Liuti and F. Cano
- Subjects
Physics ,High Energy Physics - Phenomenology ,Nuclear and High Energy Physics ,Particle physics ,High Energy Physics - Phenomenology (hep-ph) ,High Energy Physics::Lattice ,Nuclear Theory ,High Energy Physics::Phenomenology ,FOS: Physical sciences ,High Energy Physics::Experiment ,Nuclear Experiment ,Gluon - Abstract
We examine the low Bjorken $x$ gluon distribution in nuclei in the asymptotic region., Comment: 7 pages, 1 figure
- Published
- 2000
41. Observations of Chiral Odd GPDs and their Implications
- Author
-
Gary R. Goldstein, J. Osvaldo Gonzalez Hernandez, and Simonetta Liuti
- Subjects
Physics ,Angular momentum ,Particle physics ,media_common.quotation_subject ,Momentum transfer ,FOS: Physical sciences ,Parton ,Parity (physics) ,Quantum number ,Helicity ,Asymmetry ,law.invention ,High Energy Physics - Phenomenology ,High Energy Physics - Phenomenology (hep-ph) ,law ,Cartesian coordinate system ,media_common - Abstract
Our original suggestion to investigate exclusive $\pi^0$ electroproduction as a method for extracting the tensor charge, transversity, and other quantities related to chiral odd generalized parton distributions from cross section and asymmetry data is reviewed. We explain some of the details of the process: {\it i)} the connection between the helicity description and the cartesian basis; {\it ii)} the dependence on the momentum transfer squared, $Q^2$, and {\it iii)} the angular momentum, parity, and charge conjugation constraints ($J^{PC}$ quantum numbers)., Comment: 8 pages, 3 figures, Proceedings of QCD Evolution Workshop III, Jefferson Lab, May 2013
- Published
- 2013
- Full Text
- View/download PDF
42. Can a highly virtual nucleon experience final state interactions in electron-nucleus scattering?
- Author
-
Simonetta Liuti and Omar Benhar
- Subjects
Scattering amplitude ,Physics ,Momentum ,Nuclear and High Energy Physics ,Amplitude ,Eikonal equation ,Scattering ,Quantum electrodynamics ,Nuclear Theory ,Momentum transfer ,Electron ,Nuclear Experiment ,Nucleon - Abstract
We discuss how the virtuality of the struck particle may affect the final state interactions in electron-nucleus scattering. The extent to which short-range correlations inhibit rescatterings taking place within the range of the repulsive core of the nucleon-nucleon interaction is quantitatively analyzed within the eikonal approach, based on the on-shell approximation for the nucleon-nucleon scattering amplitude. The possible modifications of the amplitude associated with the virtuality are then studied within the framework of a nonrelativistic model. The results indicate that the accuracy of the on-shell approximation strongly depends upon the momentum, and turns out to be rather good in the kinematical region relevant to the analysis of the available inclusive data at large momentum transfer and low energy loss.
- Published
- 1996
43. Extraction of the ratio of the neutron to proton structure functions from deep inelastic scattering
- Author
-
Franz Gross and Simonetta Liuti
- Subjects
Physics ,Nuclear and High Energy Physics ,Particle physics ,Nuclear Theory ,Structure function ,FOS: Physical sciences ,Impulse (physics) ,Deep inelastic scattering ,European Muon Collaboration ,High Energy Physics - Phenomenology ,High Energy Physics - Phenomenology (hep-ph) ,Deuterium ,Neutron ,Nuclear Experiment ,Series expansion - Abstract
We study the nuclear ($A$) dependence of the European Muon Collaboration (EMC) effect at high values of $x$ ($x \geq 0.6$). Our approach makes use of conventional nuclear degrees of freedom within the Relativistic Impulse Approximation. By performing a non-relativistic series expansion we demonstrate that relativistic corrections make a substantial contribution to the effect at $x \gtrsim 0.6$ and show that the ratio of neutron to proton structure functions extracted from a global fit to all nuclei is not inconsistent with values obtained from the deuteron., 12 pages, 2 figures available upon request, Revtex
- Published
- 1995
44. Probing Spin Dependent Quark and Gluon Distributions Through Azimuthal and Polarization Asymmetries
- Author
-
Gary R. Goldstein and Simonetta Liuti
- Subjects
Quark ,Quantum chromodynamics ,Physics ,Particle physics ,010308 nuclear & particles physics ,QC1-999 ,High Energy Physics::Phenomenology ,Hadron ,Parton ,Observable ,Polarization (waves) ,01 natural sciences ,Helicity ,Gluon ,Nuclear physics ,0103 physical sciences ,High Energy Physics::Experiment ,Nuclear Experiment ,010306 general physics - Abstract
Spin and transverse momentum dependent parton distributions - Generalized Parton Distributions, Transverse Momentum Distributions and related distributions - are at the interface between the QCD structure of the hadrons and observable quantities. The distributions are contained as linear superpositions within helicity amplitudes that factorize into universal forms at leading or next to leading order. These amplitudes are probed in high energy leptoproduction processes through angular dependent cross sections and polarization asymmetries. The phenomenological extraction of the amplitudes and the distributions is a challenging task. We will present some models for the distributions in leptoproduction processes, as well as the observables that connect with the quark-nucleon helicity amplitudes for different Deeply Virtual production possibilities.
- Published
- 2016
45. The Strong Coupling Constant from Hadron Structure Phenomenology
- Author
-
Aurore Courtoy and Simonetta Liuti
- Subjects
Quantum chromodynamics ,Coupling constant ,Physics ,Particle physics ,High Energy Physics::Lattice ,Hadron ,High Energy Physics::Phenomenology ,Perturbative QCD ,FOS: Physical sciences ,Electron ,Lambda ,High Energy Physics - Phenomenology ,High Energy Physics - Phenomenology (hep-ph) ,Strong coupling ,High Energy Physics::Experiment ,Phenomenology (particle physics) - Abstract
We present recent developments on the role of the running coupling constant at the intersection of perturbative and nonperturbative QCD. A number of experiments show a smooth transition from small to large scales given by the four-momentum transfer in the reactions. This is at variance with perturbative QCD where the running coupling constant becomes infinite when the scale equals $\Lambda_{{\tiny QCD}}$. Approaches using an effective coupling constant could help interpret the opposite trend of data as compared to standard perturbative QCD predictions. We give an overview of the role of the coupling constant in the procedure to match nonperturbative hadronic model to perturbative QCD and we propose an extraction of an effective coupling constant from inclusive electron proton scattering data at large Bjorken x., Comment: To appear in the proceedings of the QCD Evolution Workshop, JLab, May 14-17, 2012. Includes ws-ijmpcs.cls
- Published
- 2012
46. A flexible parameterization of GPDs, their role in DVCS, neutral meson leptoproduction
- Author
-
Simonetta Liuti, Gary R. Goldstein, and J. Osvaldo Gonzalez Hernandez
- Subjects
Physics ,Particle physics ,Meson ,High Energy Physics::Phenomenology ,Lattice field theory ,Observable ,Parton ,Deep inelastic scattering ,Helicity ,Nuclear physics ,Diquark ,High Energy Physics::Experiment ,Nuclear Experiment ,Nucleon - Abstract
A physically motivated parameterization of the chiral-even generalized parton distributions (GPDs) has been obtained from a global analysis using available experimental data including nucleon electromagnetic form factors, deep inelastic scattering and DVCS. Additional information provided by lattice calculations of the higher moments of GPDs is also considered. Recently extracted observables from DVCS at JLab and Hermes are reproduced by our fit and predictions are made for higher energy regimes. Our scheme uses a Reggeized diquark model and concomitant helicity amplitude relations, which allow the extension to the chiral-odd sector. Having obtained the chiral-odd GPDs, we are able to explain the features of exclusive neutral meson electroproduction. Our analysis is applied to existing and forthcoming spin-dependent π0 and η data in the kinematical region of intermediate Bjorken x and Q2 in the multi-GeV region, accessible at present and currently planned facilities.
- Published
- 2012
47. Interpretation of the Flavor Dependence of Nucleon Form Factors in a Generalized Parton Distribution Model
- Author
-
J. Osvaldo Gonzalez-Hernandez, Kunal Kathuria, Gary R. Goldstein, and Simonetta Liuti
- Subjects
Quark ,Physics ,Nuclear and High Energy Physics ,Particle physics ,Angular momentum ,High Energy Physics::Lattice ,Momentum transfer ,High Energy Physics::Phenomenology ,FOS: Physical sciences ,Parton ,Interpretation (model theory) ,Diquark ,Momentum ,High Energy Physics - Phenomenology ,High Energy Physics - Phenomenology (hep-ph) ,High Energy Physics::Experiment ,Nucleon ,Nuclear Experiment - Abstract
We give an interpretation of the $u$ and $d$ quarks contributions to the nucleon electromagnetic form factors for values of the four-momentum transfer in the multi-GeV region where flavor separated data have been recently made available. The data show, in particular, a suppression of $d$ quarks with respect to $u$ quarks at large momentum transfer. %and constant ratios of the flavor dependent Pauli to Dirac form factors ratios. This trend can be explained using a reggeized diquark model calculation of generalized parton distributions, thus providing a correlation between momentum and coordinate spaces, both of which are necessary in order to interpret the partonic substructure of the form factors. We extend our discussion to the second moments of generalized parton distributions which are believed to contribute to partonic angular momentum., Comment: 22 pages, 19 figures; results and figures added and changed, tables added, formulae added, major rewriting of text
- Published
- 2012
- Full Text
- View/download PDF
48. Easy as π o: On the interpretation of recent electroproduction results
- Author
-
Gary R. Goldstein, J. Osvaldo Gonzalez Hernandez, and Simonetta Liuti
- Subjects
Physics ,Nuclear and High Energy Physics ,Particle physics ,Angular momentum ,Momentum transfer ,Parton ,Parity (physics) ,Quantum number ,Helicity ,law.invention ,High Energy Physics - Phenomenology ,law ,Cartesian coordinate system ,Nuclear Experiment ,Nucleon - Abstract
Exclusive $\pi^o$ electroproduction from nucleons was first suggested by Ahmad, Goldstein and Liuti for extracting from experimental data the tensor charge, transversity and other quantities related to chiral odd combinations of generalized parton distributions. We now explain the details of the process: {\it i)} the connection between the helicity description and the cartesian basis; {\it ii)} the dependence on the momentum transfer squared, $Q^2$, and {\it iii)} the angular momentum, parity, and charge conjugation constraints ($J^{PC}$ quantum numbers)., Comment: 15 pages, 2 figures, some changes in formalism, and text. Introduced section titles
- Published
- 2012
49. Self-Organizing Maps Algorithm for Parton Distribution Functions Extraction
- Author
-
Evan Askanazi, Katherine Holcomb, and Simonetta Liuti
- Subjects
Self-organizing map ,History ,Computer science ,Scattering ,High Energy Physics::Phenomenology ,FOS: Physical sciences ,Probability and statistics ,Parton ,Extension (predicate logic) ,Computer Science Applications ,Education ,Matrix (mathematics) ,High Energy Physics - Phenomenology ,High Energy Physics - Phenomenology (hep-ph) ,Distribution function ,Physics - Data Analysis, Statistics and Probability ,Complex class ,High Energy Physics::Experiment ,Nuclear Experiment ,Algorithm ,Data Analysis, Statistics and Probability (physics.data-an) - Abstract
We describe a new method to extract parton distribution functions from hard scattering processes based on Self-Organizing Maps. The extension to a larger, and more complex class of soft matrix elements, including generalized parton distributions is also discussed., 6 pages, 3 figures, to be published in the proceedings of ACAT 2011, 14th International Workshop on Advanced Computing and Analysis Techniques in Physics Research
- Published
- 2011
50. PQCD Analysis of Parton-Hadron Duality
- Author
-
Simonetta Liuti
- Subjects
Quantum chromodynamics ,Physics ,Coupling constant ,Particle physics ,High Energy Physics - Phenomenology ,High Energy Physics - Phenomenology (hep-ph) ,Hadron ,FOS: Physical sciences ,Observable ,Invariant mass ,Parton ,Twist ,Resummation - Abstract
We propose an extraction of the running coupling constant of QCD in the infrared region from experimental data on deep inelastic inclusive scattering at Bjorken x -> 1. We first attempt a perturbative fit of the data that extends NLO PQCD evolution to large x values and final state invariant mass, W, in the resonance region. We include both target mass corrections and large x resummation effects. These effects are of order O(1/Q^2), and they improve the agreement with the Q^2 dependence of the data. Standard analyses require the presence of additional power corrections, or dynamical higher twists, to achieve a fully quantitative fit. Our analysis, however, is regulated by the value of the strong coupling in the infrared region that enters through large x resummation effects, and that can suppress, or absorb, higher twist effects. Large x data therefore indirectly provide a measurement of this quantity that can be compared to extractions from other observables., 10 pages, 3 figures
- Published
- 2011
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