Search

At temperatures above ∼5 keV, the non-relativistic approximation used to derive the classical thermal Sunyaev-Zel'dovich effect spectrum begins to fail. When relativistic effects are included, the spectrum becomes temperature-dependent. This leads to both a problem and an opportunity: a problem, because when the temperature dependence is not accounted for the Compton-y estimate is biased; and an opportunity, because it represents a new way to measure the temperature of the intracluster medium independently of X-ray observations. This work presents current results from investigating the impact of relativistic effects on Planck cluster observations, and projections for future measurements of cluster temperatures using the Atacama Large Aperture Sub-millimetre Telescope. [ABSTRACT FROM AUTHOR]

The abundance of galaxy clusters with mass and redshift is a wellknown cosmological probe. The cluster mass is a key parameter for studies that aim to constrain cosmological parameters using galaxy clusters, making it critical to understand and properly account for the errors in its estimates. Subsequently, it becomes important to correctly calibrate scaling relations between observables like the integrated Compton parameter and the mass of the cluster. The NIKA2 Sunyaev-Zeldovich Large program (LPSZ) enables one to map the intracluster medium profiles in the mm–wavelength band with great details (resolution of 11 & 17″ at 1.2 & 2 mm, respectively) and hence, to estimate the cluster hydrostatic mass more precisely than previous SZ observations. However, there are certain systematic effects which can only be accounted for with the use of simulations. For this purpose, we employ The Three Hundred simulations which have been modelled with a range of physics modules to simulate galaxy clusters. The so-called twin samples are constructed by picking synthetic clusters of galaxies with properties close to the observational targets of the LPSZ. In particular, we use the Compton parameter maps and projected total mass maps of these twin samples along 29 different lines of sight. We investigate the scatter that projection induces on the total masses. Eventually, we consider the statistical values along different lines of sight to construct a kind of 3D scaling law between the integrated Compton parameter, total mass, and overdensity of the galaxy clusters to determine the overdensity that is least impacted by the projection effect. [ABSTRACT FROM AUTHOR]

In cluster cosmology, cluster masses are the main parameter of interest. They are needed to constrain cosmological parameters through the cluster number count. As the mass is not an observable, a scaling relation is needed to link cluster masses to the integrated Compton parameters Y, i.e. the Sunyaev-Zeldovich observable (SZ). Planck cosmological results obtained with cluster number counts are based on a scaling relation measured with clusters at low redshift (z<0.5) observed in SZ and X-ray. In the SZ Large Program (LPSZ) of the NIKA2 collaboration, the scaling relation will be obtained with a sample of 38 clusters at intermediate to high redshift (0.5 < z < 0.9) and observed at high angular resolution in both SZ and X-ray. Thanks to analytical simulation of LPSZ-like samples, we take into account the LPSZ selection function and correct for its effects. Besides, we show that white and correlated noises in the SZ maps do not affect the scaling relation estimation. [ABSTRACT FROM AUTHOR]

The study of the morphology of 2D projected maps of galaxy clusters is a suitable approach to infer, from real data, the dynamical state of those systems. We recently developed a new method to recover the morphological features in galaxy cluster maps which consists of an analytical modelling through the Zernike polynomials. The validation of this approach was done on a set of high-resolution mock maps of the Compton parameter y. These maps are from hydrodynamically simulated galaxy clusters in The Three Hundred project. After this step, we apply the Zernike modelling on y-maps of local (z < 0.1) galaxy clusters observed by the Planck satellite. With a single parameter collecting the main information of the Zernike modelling, we classify their morphology. A set of mock Planck-like y-maps, generated from The Three Hundred clusters, is also used to validate our indicator with a proper dynamical state classification. This approach allows us to test the efficiency of the Zernike morphological modelling in evaluating the dynamical population in the real Planck sample. [ABSTRACT FROM AUTHOR]

High-precision spectroscopy of the Cosmic Microwave Background (CMB) is one of the three themes that have been selected by the ESA Voyage 2050 programme. Several space missions dedicated to the measurement of the CMB spectral distortions such as PIXIE, PRISTINE, and FOSSIL have been proposed since 2011. Additionally, balloon-borne projects, such as BISOU, have also been considered as a pathfinder for a future space mission. This paper presents an effort undertaken to define future missions and instruments dedicated to the measurement of the CMB spectral distortions. For this purpose, models allowing to optimize both instrument concept and mission parameters (mission duration, scanning strategy, ...) have been developed. It has been applied to two specific cases, FOSSIL, a space mission proposed to answer the ESA M7 call in 2022 , and BISOU, a CNES Phase 0 study for a balloon-borne mission. [ABSTRACT FROM AUTHOR]

In 2015, the Planck Collaboration released an all-sky map of the thermal Sunyaev-Zeldovich (SZ) effect, obtained by implementing the needlet internal linear combination (NILC) method on the Planck PR2 data. The quality of the Planck data has significantly improved since then. The Planck PR4 data release offers upgraded full-sky maps in the LFI and HFI frequency bands with improved systematics and sensitivity. We present a new all-sky thermal SZ Compton y-parameter map derived from the Planck PR4 data using NILC and highlight improvements, particularly in noise reduction and handling residual foreground contamination. The PR4 NILC Compton y-parameter map has been made publicly available to support further analyses. [ABSTRACT FROM AUTHOR]

A specific objective of the recent IAEA Coordinated Research Project on Photonuclear Data and Photon Strength Functions (Code F41032; Duration 2016-2019) has been to measure photonuclear cross-section data where needed, for unexplored nuclei and cases of discrepant existing data. A dedicated experimental campaign has been conducted at the laser Compton-scattering γ-ray source of the NewSUBARU synchrotron radiation facility of SPring8, Japan, where photoneutron reactions for 11 nuclei from 9Be to 209Bi have been investigated in the Giant Dipole Resonance energy region. The measurements followed the development of a flat-effi ciency moderated neutron detection array and the associated neutron-multiplicity sorting techniques. The IAEA CRP campaign has been followed at NewSUBARU by new measurements of photofission and photoneutron reactions on 238U and 232Th in the energy range of 5.87 MeV – 20.14 MeV. The neutron-multiplicity sorting of high-multiplicity fission neutron coincidence events has been performed using a dedicated energy dependent, multiple firing statistical treatment. The photoneutron (γ, xn) and photofission (γ, fxn) reactions have been discriminated by considering a Gaussian distribution of prompt-fission-neutrons (PFN) multiplicities predicted by the evaporation theory. We here provide preliminary experimental (γ, n), (γ, 2n) and (γ, F) cross sections, average energies of PFN and of photoneutrons emitted in (γ, n) and (γ, 2n) reactions, as well as the mean number of PFN per fission act. The new 238U cross sections are compared with recent statistical-model calculations performed with the EMPIRE code on existing data. [ABSTRACT FROM AUTHOR]

Photoneutron reactions on 208Pb in the Giant Dipole Resonance (GDR) energy range have been investigated at the γ-ray beam line of the NewSUBARU synchrotron radiation facility in Japan. Making use of quasi-monochromatic laser Compton scattering (LCS) γ-ray beams and of a novel flat-efficiency neutron detection system along with associated neutron-multiplicity sorting method, total and partial (γ,xn) photoneutron cross sections with x = 1 to 4 have been measured for 208Pb in a broad energy range covering the neutron threshold up to 38 MeV. [ABSTRACT FROM AUTHOR]

The Electron-Ion Collider (EIC) is a future collider planned to be built at BNL in about a decade. It will provide physicists with high luminosity and highly polarized beams with a wide range of nuclei species at different energies, covering an extensive kinematic range. The EIC physics goals include measuring the Generalized Parton Distribution (GPD) from Deeply Virtual Compton Scattering (DVCS) and Deeply Virtual Meson Production (DVMP) experiments, performing precision 3D imaging of the nuclei structure, studying color confinement and hadronization mechanisms, and understanding the spin structure of the proton. In order to meet the physics goals of EIC, a highresolution electromagnetic calorimeter (EMCAL) is required to measure electrons and photons and to achieve good particle identification. We propose to develop a tungsten/shashlik (W/shashlik) EMCAL with better readout configuration to achieve better energy and position resolution. In this work, we will present the GEANT4 detector simulation results ofWand Pb shashlik EMCAL to study π0 merging probability as a function of π0 energy and the performance of position and energy resolutions of the EMCAL for ECCE design. [ABSTRACT FROM AUTHOR]

The processing of experimental data for the photon induced reactions on 238U and 232Th investigated by quasi-monochromatic γ-ray beams (produced in Laser Compton scattering at the NewSUBARU facility) needs the prediction of prompt neutron spectra. They are obtained using reliable models and systematics, i.e. the most employed and well validated approach of the most probable fragmentation with input parameters provided by a recent systematic and fission chance probabilities based on nuclear reaction calculations performed with the EMPIRE code. [ABSTRACT FROM AUTHOR]

Obtaining directional information is required in many applications such as nuclear homeland security, contamination mapping after a nuclear incident and radiological events, or during the decontamination work. However, many directional radiation detectors are based on directional shielding, made of lead or tungsten collimators, introducing two main drawbacks. The first is the size and weight, making those detectors too heavy and irrelevant for utilization in handheld devices, drone mapping, or space applications. The second drawback is the limited field of view, which requires multiple detectors to cover the whole required field of view or machinery to rotate the narrow field of view detector. We propose a novel 4π directional detector based on a segmented hollow cubic detector, which uses the Compton effect interactions with no heavy collimators. The symmetrical cubical design provides both higher efficiency and 4π detection ability. Instead of traditional two types of detectors (scatterer and absorber) structure, we use the same type of detector, based on GAGG(Ce) scintillator coupled to silicon photomultiplier. Additional advantage of the proposed detector obtained by locating the photon sensors inside the detector, behind the scintillators, which improves the radiation hardness required for space applications. Furthermore, such arrangement flattens the temperature variation across the detector, providing better gain stability. The main advantage of the proposed detector is the ability of 4pi radiation detection for high energy gamma-rays without the use of heavy collimators. [ABSTRACT FROM AUTHOR]

This paper presents the most recent progress on the development of gamma transport capability for the CASL neutronics code MPACT: (1) 3D gamma transport and (2) explicit gamma heating capabilities. The 3D gamma calculation capability was implemented by leveraging the 2D/1D solver originally developed for neutron calculations. The results were verified by MCNP6 on a small assembly with 5 × 5 pins. Generally, errors were lower than 0.5% on each axial mesh as long as MPACT was running with enough axial meshes. The gamma heating calculation considered the energy deposition from photoelectric absorption, Compton scattering, and pair production. Verification with MCNP6 for both 2D and 3D benchmarks showed that the errors of energy depositions are comparable with those of gamma fluxes, proving the proper implementation of the energy deposition. [ABSTRACT FROM AUTHOR]

Contemporary CO2 laser systems are capable to delivering picosecond pulses of the multi-terawatt peak power. Further pulse compression to a few cycles is possible using a post-compression in bulk materials with negative group velocity dispersion (GVD). We have experimentally demonstrated the post-compression of a long-wave infrared (9.2 μm) 150-GW peak power pulse from 1.85 ps to less than 500 fs using a combination of two optical materials with significantly different ratios of the nonlinear refractive index to the GVD coefficient. Such combination allows for optimization of the compression mechanism and promises a viable path to scaling peak powers to multi-terawatt levels. [ABSTRACT FROM AUTHOR]

We discuss an alternative picture of neutrino oscillation. In this phenomenological model, the flavor-changing phenomena of massless neutrinos arise from scattering processes between neutrinos and four types of undetected spin-0 massive particles pervading throughout the Universe, instead of neutrinos' own nature. These scattering processes are kinematically similar to Compton scattering. One type of left-handed massless sterile neutrino is needed in order to reproduce the neutrino oscillation modes predicted in the theory of neutrino mixing. Implications of our model include the existence of sterile neu- trinos, the nonconservation of active neutrinos, the possible mismatch among three neutrino mass squared differences ∆m2ij interpreted in the theory of neutrino mixing, the spacetime dependence of neutrino oscillation, and the impossibility of neutrinoless double beta decay. Several important open problems in neutrino physics become trivial or less severe in our model, such as the smallness of neutrino masses, neutrino mass hierarchy, the mechanism responsible for neutrino masses, and the Dirac/Majorana nature of neutrinos. [ABSTRACT FROM AUTHOR]

Gamma logging for uranium exploration are currently based on total counting with Geiger Müller gas detectors or NaI (TI) scintillators. However, the total count rate interpretation in terms of uranium concentration may be impaired in case of roll fronts, when the radioactive equilibrium of the natural 238U radioactive chain is modified by differential leaching of uranium and its daughter radioisotopes of thorium, radium, radon, etc. Indeed, in case of secular equilibrium, more than 95 % of gamma rays emitted by uranium ores come from 214Pb and 214Bi isotopes, which are in the back-end of 238U chain. Consequently, these last might produce an intense gamma signal even when uranium is not present, or with a much smaller activity, in the ore. Therefore, gamma spectroscopy measurements of core samples are performed in surface with high-resolution hyper-pure germanium HPGe detectors to directly characterize uranium activity from the 1001 keV gamma ray of 234mPa, which is in the beginning of 238U chain. However, due to the low intensity of this gamma ray, i.e. 0.84 %, acquisitions of several hours are needed. In view to characterize uranium concentration within a few minutes, we propose here a method using both the 92 keV gamma ray of 234Th and the 98.4 keV uranium X-ray. This last is due to uranium self-induced fluorescence caused by gamma radiations of 214Pb and 214Bi, which create a significant Compton scattering continuum acting as a fluorescence source and resulting in the emission of uranium fluorescence X-rays. The comparison of the uranium activity obtained with the 92 keV and 98.4 keV lines allows detecting a uranium heterogeneity in the ore. Indeed, in case of uranium nugget, the 92 keV line leads to underestimated uranium concentration due to gamma self-absorption, but on the contrary the 98.4 keV line leads to an overestimation because of increased fluorescence. In order to test this new approach, several tens of uranium ore samples have been measured with a handheld HPGe FALCON 5000 detector. [ABSTRACT FROM AUTHOR]

A scan of the threshold region of the process e+e−→ τ+τ− with integrated luminosity about 140 pb−1 was performed with the BES-III detector at the BEPC-II collider in order to measure the τ-lepton mass. The beam energy was determined by the Compton backscattering method. To verify the measurement accuracy scans of the J/ψ and ψ′ resonances were performed. [ABSTRACT FROM AUTHOR]

Possible connection between visible and hidden Worlds of particle physics is provided by the vector portal interaction, that is kinetic mixing between ordinary (visible) and hidden photons. If sufficiently light, the hidden photon can be produced (and absorbed) by ordinary matter in a Compton-like processes, which naively are insensitive to the hidden photon mass. In this talk we study the evolution of the two vector boson system, which exhibits oscillations similar to the well-known neutrino oscillations. We show that, provided by the environment matter, this quantum phenomenon significantly suppresses the hidden photon production in particle collisions. The ordinary photon is effectively massive in the media. The suppression is important for hidden photon lighter than photon in the corresponding media (detector, beam dump material etc) and grows with decrease of the hidden photon mass making all the accelerator and reactor experiments absolutely insensitive to the models with light photons. The dedicated study is required for the case of the degenerate photon and hidden photon, when, on the contrary, the hidden photon production can be amplified with respect to the Compton process. [ABSTRACT FROM AUTHOR]

Three-dimensional tomography of hadrons can be investigated by generalized parton distributions (GPDs), transverse-momentum-dependent parton distributions (TMDs), and generalized distribution amplitudes (GDAs). The GDA studies had been only theoretical for a long time because there was no experimental measurement until recently, whereas the GPDs and TMDs have been investigated extensively by deeply vir- tual Compton scattering and semi-inclusive deep inelastic scattering. Here, we report our studies to determine pion GDAs from recent KEKB measurements on the differen- tial cross section of γ*γ → π0π0. Since an exotic-hadron pair can be produced in the final state, the GDAs can be used also for probing internal structure of exotic hadron candidates in future. The other important feature of the GDAs is that the GDAs contain information on form factors of the energy-momentum tensor for quarks and gluons, so that gravitational form factors and radii can be calculated from the determined GDAs. We show the mass (energy) and the mechanical (pressure, shear force) form factors and radii for the pion. Our analysis should be the first attempt for obtaining gravitational form factors and radii of hadrons by analysis of actual experimental measurements. We believe that a new field of gravitational physics is created from the microscopic level in terms of elementary quarks and gluons. [ABSTRACT FROM AUTHOR]

μX-ray spectra for Z=9-90 were measured with HPGe detectors and muonic beams of PSI (Villigen, Switzerland) [1]. The results are presented as electronic atlas composed of graphic plots. The atlas is available at JINR site [2]. [ABSTRACT FROM AUTHOR]

Photo-neutron energy spectra for Eg=23.1 and 26.6 MeV mono-energetic photons on natC were measured using laser Compton scattering facility at NewSUBARU BL01. The photon energy spectra were evaluated through measurements and simulations with collimator sizes and arrangements for the laser electron photon. The neutron energy spectra for the nattC(g,xn) reaction were measured at 60 degrees in horizontal and 90 degrees in horizontal and vertical with respect to incident photon. The spectra show almost isotropic angular distribution and flat energy distribution from detection threshold to upper limit defined by reaction Q-value. [ABSTRACT FROM AUTHOR]

The A2 collaboration at the Mainz Microtron has undertaken a program of Compton scattering experiments with the goal of extracting the proton and, in the future, neutron polarizabilities. These are fundamental parameters that describe the response of the nucleon to an electromagnetic field. An extraction of these parameters will provide a crucial test of QCD theories. This talk presented the concept and status of this program, including some preliminary results. [ABSTRACT FROM AUTHOR]

The last six years have witnessed major revisions of our knowledge about the Crab Pulsar. The consensus scenario for the origin of the high-energy pulsed emission has been challenged with the discovery of a very-high-energy power law tail extending up to ∼400 GeV, above the expected spectral cut off at a few GeV. Now, new measurements obtained by the MAGIC collaboration extend the energy spectrum of the Crab Pulsar even further, on the TeV regime. Above ∼400 GeV the pulsed emission comes mainly from the interpulse, which becomes more prominent with energy due to a harder spectral index. These findings require γ-ray production via inverse Compton scattering close to or beyond the light cylinder radius by an underlying particle population with Lorentz factors greater than 5 × 106. We will present those new results and discuss the implications in our current knowledge concerning pulsar environments. [ABSTRACT FROM AUTHOR]

The study of Compton scattering-S + γ → S + γ-at MAMI and elsewhere has led to a relatively successful understanding of proton structure via its polarizabilities. The recent observation of gravitational radiation observed by LIGO has raised the need for a parallel understanding of gravitational Compton scattering-S + g → S + g-and we show here how it can be obtained from ordinary Compton scattering by use of the double copy theorem. [ABSTRACT FROM AUTHOR]

The values of charged pion polarizabilities obtained in the framework of chiral perturbation theory at the level of two-loop accuracy are compared with the experimental result recently reported by COMPASS Collaboration. It is found that the calculated value for the dipole polarizabilities (α - β)π± = (5.7 ± 1.0) × 10-4 fm3 fits quite well the experimental result (α - β)π± = (4.0 ± 1.2stat ± 1.4syst) × 10-4 fm3. [ABSTRACT FROM AUTHOR]

The process of the photon splitting, γ → γγ, is investigated in the presence of strongly magnetized charge-asymmetric cold plasma. The dispersion properties of photons and the new polarization selection rules are obtained in such plasma. The absorption rate of the leading photon splitting channel are calculated with taking account of the photon dispersion and wave function renormalization. In addition, a comparison of the photon splitting and the Compton scattering processes is performed. [ABSTRACT FROM AUTHOR]

In this manuscript we review the challenges of Compton backscattering sources in advancing photon beam performances in the 1 - 20 MeV energy range, underlining the design criteria bringing to maximum spectral luminosity and briefly describing the main achievements in conceiving and developing new devices (multi-bunch RF cavities and Laser recirculators) for the case of ELI-NP Gamma Beam System (ELI-NP-GBS). [ABSTRACT FROM AUTHOR]

The COMPTON@MAX-lab collaboration has recently published a new measurement of elastic photon scattering from deuterium using tagged photons at the MAX IV Laboratory [1]. The experiment utilized the Tagged Photon Facility at MAX IV and three of the largest NaI(Tl) detectors in the world. Correction terms to the cross section were determined via Monte Carlo simulations [2, 3] and were confirmed by comparisons to the well-known 12C(γ,γ)12C reaction [4]. These results represent the most extensive data on deuteron Compton scattering ever measured and effectively double the world data set. In addition, the energy range overlaps previous experiments and extends nearly 20 MeV higher where the sensitivity to the polarizabilities is enhanced. As a result, we have obtained the neutron polarizabilities as αn=[11.55 ± 1.25(stat) ± 0.2(BSR) ± 0.8(th)] × 10-4 fm3 and βn=[3.65 ± 1.25(stat) ± 0.2(BSR) ± 0.8(th)] × 10-4 fm3, which represents a 30% reduction in the statistical uncertainty [ABSTRACT FROM AUTHOR]

We review theoretical progress and prospects to understand the nucleon's static dipole polarisabilities from Compton scattering on few-nucleon targets, including new values; see Refs. [1-5] for details and a more thorough bibliography. [ABSTRACT FROM AUTHOR]

The searching of saturation effects in inclusive and exclusive eA collisions is reviewed. In particular, we present a comparison between the linear and non-linear predictions for the nuclear structure functions as well as for the Deep Virtual Compton Scattering and vector meson production in future eA colliders. [ABSTRACT FROM AUTHOR]

Exclusive processes of heavy meson production and spacelike and timelike deeply virtual Compton scattering allow us to investigate the hadron structure in terms of Generalized Parton Distributions (GPDs). We review recent developments in the NLO description of such processes. [ABSTRACT FROM AUTHOR]

S. Brodsky, F.J. Llanes-Estrada and A. Szczepaniak formulated the J = 0 fixed pole universality hypothesis for (deeply) virtual Compton scattering. We show that in the Bjorken limit this hypothesis is equivalent to the validity of the inverse moment sum rule for the D-term form factor. However, any supplementary D-term added to a generalized parton distribution (GPD) results in an additional J = 0 fixed pole contribution that violates universality. Unfortunately, one can not provide any reliable theoretical argument excluding the existence of such supplementary D-term. Moreover, the violation of J = 0 fixed pole universality was revealed in field theoretical GPD models. Therefore, J = 0 fixed pole universality hypothesis remains just an external assumption and probably will never be proven theoretically. [ABSTRACT FROM AUTHOR]

We review the dispersion relation formalism for the deeply virtual Compton scattering amplitudes, and derive a dispersive representation of the D-term form factor, using unsubtracted t-channel dispersion relations. Results for the D-term form factor as function of t as well as at t = 0 are shown in comparison with available model predictions and phenomenological parametrizations. [ABSTRACT FROM AUTHOR]

Having in mind the well-known limitations of certain models of generalized parton distributions (GPDs), we show that the allegedly universal GPDs, describing both deeply virtual Compton scattering (DVCS) and deeply virtual meson production (DVMP) data, fail to describe measurements of deep inelastic scattering. We present a new global DVCS fit that describes reasonably the world data set, which includes now also new measurements from Hall A and CLAS collaborations. We also explicitly illustrate that Compton form factors (CFFs) cannot be unambiguously extracted from photon electroproduction measurements off unpolarized proton alone and we argue that it is more reliable to interpret such measurements in terms of certain CFF combinations, where still some care is needed in order to estimate the propagated error. [ABSTRACT FROM AUTHOR]

Existing data for the electromagnetic proton form factors and for the cross section of the wide angle Compton scattering (WACS) show that the hard two-gluon exchange mechanism (collinear factorization) is still not applicable in the kinematical region where Mandelstam variables s ~ -t ~ -u are about few GeV². On the other hand these observables can be described in phenomenological models where spectator quarks are soft which assumes a large contribution due to the soft-overlap mechanism. It turns out that the simple QCD factorization picture is not complete and must also include the soft-overlap contribution which can be described as a certain matrix element in the soft collinear effective theory (SCET). Then the leading power contribution to WACS amplitude is described as a sum of the hard- and soft-spectator contributions. The existing experimental data allows one to check certain conclusions based on the assumption about dominant role of the soft-spectator mechanism. [ABSTRACT FROM AUTHOR]

This paper gives the preliminary results of the experimental cross section for deeply virtual Compton scattering on the neutron (en → enγ). The E08-025 experiment was performed at Jefferson Lab Hall A.We measured the (D(e, eX-H(e, e'γ)X) unpolarized cross section and we extracted, for the first time, a non-zero contribution of (neutron-DVCS + coherent-deuteron-DVCS) at Q² = 1.75 GeV² and xB = 0.36. [ABSTRACT FROM AUTHOR]

The JLAB EIC (JLEIC) design includes a chicane after the interaction point to detect electron associated with production of quasi-real photon at the interaction. This chicane layout can also be used for Compton polarimetry to measure the electron beam polarization. This proceeding will present the layout of the low Q² chicane and the implementation and current R&D of a Compton polarimeter which would be located in the middle of this chicane. [ABSTRACT FROM AUTHOR]

Photoproduction of a pair of particles with large invariant mass is a natural extension of collinear QCD factorization theorems which have been much studied for deeply virtual Compton scattering and deeply virtual meson production. We discuss the production of a photon and a meson, where the wide angle Compton scattering on a meson subprocess factorizes from generalized parton distribution. We calculate at dominant twist and leading order in αs, the production cross-section of a transversely polarized ρ meson which is sensitive to chiral-odd GPDs, and show that it may be measurable in near future JLab experiments. [ABSTRACT FROM AUTHOR]

Hard exclusive processes such as photoproduction or electroproduction of photon or meson off the nucleon provide access to the Generalized Parton Distributions (GPDs), in the regime where the scattering amplitude is factorized into a hard and a soft part. GPDs contain the correlation between the longitudinal momentum fraction and the transverse spatial densities of quarks and gluons in the nucleon. Timelike Compton Scattering (TCS) correspond to the reaction γN → γ*N → e*e-N, where the photon is scattered off a quark. It is measured through its interference with the associated Bethe-Heitler process, which has the same final state. TCS allows to access the GPDs and test their universality by comparison to the results obtained with the DVCS process (eN → eγN). Also, results obtained with TCS provide additional independent constrains to the GPDs parameterization. We will present the physical motivations for TCS, with our theoretical predictions for TCS observables and their dependencies. We calculated for JLab 12 GeV energies all the single and double beam and/or target polarization observables off the proton and off the neutron. We will also present the experimental perspectives for the next years at JLab. Two proposals were already accepted at JLab: in Hall B, with the CLAS12 spectrometer, in order to measure the unpolarized cross section and in Hall A, with the SoLID spectrometer, in order to measure the unpolarized cross section and the beam spin asymmetry at high intensity. A Letter Of Intent was also submitted in order to measure the transverse target spin asymmetries in Hall C. We will discuss the merits of this different experiments and present some of the expected results. [ABSTRACT FROM AUTHOR]

The Extreme Light Infrastructure - Nuclear Physics facility is dedicated to nuclear physics studies with the use of extreme electromagnetic radiation. One of the main research system to be installed and operated in the facility is an outstanding high brilliance gamma beam system. The Gamma Beam System of ELI--NP will produce intense, quasi--monochromatic gamma beams via inverse Compton scattering of short laser pulses on relativistic electron beam pulses. The gamma beams available at ELI--NP will allow for the performance of photo-nuclear reactions aiming to reveal the intimate structure of the atomic nucleus. Nuclear Resonance Fluorescence, photo-fission, photo-disintegration reactions above the particle threshold will be used to study the dipole response of nuclei, the structure of the Pygmy resonances, nuclear processes relevant for astrophysics, production and study of exotic neutron--rich nuclei. [ABSTRACT FROM AUTHOR]

Galactic Centre is a bright γ -ray source with the GeV-TeV band spectrum composed of two distinct components in the 1-10 GeV and 1-10 TeV energy ranges. The nature of the two components is not clearly understood.We report the analysis of the data of 74 months of observations of the Galactic Center by Fermi/LAT γ -ray telescope with the goal to constrain the morphology of the source and the nature of the two components. Spatially the Galactic Center is consistent with a point source with 0.13° 3σ upper limit on its radius. We use the Fermi/LAT data in the energy band below 100MeV to show that the γ -ray emission from the Galactic Centre source can't be explained within the pure hadronic model and discuss the necessary modifications to make the model to be consistent with the observational data. We also discuss an alternative self-consistent interpretation of the 60MeV-30 TeV spectrum of the source by a model in which the signal is produced via inverse Compton scattering of the ambient infrared radiation field. [ABSTRACT FROM AUTHOR]

Nowadays, the use of nuclear density gauges, due to the ability to work in harsh industrial environments, is very common. In this study, to reduce error related to the p of continuous measuring density, the combination of backscatter and transmission are used simultaneously. For this reason, a 137Cs source for Compton scattering dominance and two detectors are simulated by MCNP4C code for measuring the density of 3 materials. Important advantages of this combined radiometric gauge are diminished influence of µ and therefore improving linear regression. [ABSTRACT FROM AUTHOR]

Existing PET (Positron Emission Tomography) systems make clear images in demonstration (measuring small PET reagent in pure water), however images in real diagnosis become unclear. The authors suspected that this problem was caused by Compton scattering in a detector. When PET systems observe plural photomultiplier tube outputs, an original emission point is regarded as centroid of the outputs. However, even if plural emission in Compton scattering occur, these systems calculate original point in the same way as single emission. Therefore, the authors considered that rejecting Compton scattering events makes PET systems much better, and made prototype counter. Main components of the prototype counter are plate-like high-growth-rate (HGR) La-GPS scintillators and wavelength shifting fibers (WLSF). HGR crystals grow 10 times as fast as a mono-crystal (a normal mono-crystal grows at 2 - 3 mm an hour). Thus, it includes microbubble and its transparency get worth. Consequently, HGR crystals usually are not used in radiation measuring instruments. However, this time they are used on the purpose. Because of their low transparency, scintillation lights come out right above and right under of emission position. Therefore, Compton scattering events is rejected easily. The prototype detector has an effective area of 300 by 300 square mm. The detector consists of 24 layers. One layer consists of HGR La-GPS scintillator of 1 mm thickness. Top and bottom surface of scintillator were covered by dual sheets of WLSF with a diameter of 0.2 mm. Sheets of WLSF on top and bottom of the scintillator make a right angle with each other, and measure X- and Y-components. Z-component is measured by difference of WLSF outputs between top and bottom. If plural layers output signals, this counter regards the event as Compton scattering event, and reject the event. Even if only a layer output signals, the event is rejected when number output signals from WLSF is more than 1.5 times of single emission. Material cost of this system is, 0.2M$ for HGR La-GPS, 0.03M$ for WLSF, 0.03M$ for 600 units of 6 by 6 mm SiPM's, 0.12M$ for 12000 units of 1 by 1 mm SiPM's, and 0.09M$ for 1800 channel of signal readout circuits. Considering total cost, price of this PET will be set 1M$ or less. This idea was confirmed with numerical simulation and experimentation. In experimentation, position resolution in photoelectric absorption was 0.2 mm, and minimum distance that this detector could recognize plural emission in Compton scattering was 1 mm. In parallel, three kinds of model were made: a prototype detector, all the signals readout method, and resistance delay method. Simulation setting was 2 MBq/L in normal tissue and 10 MBq/L in cancer. As a result of simulation, a prototype detector identified 3 mm cancer, however the others made unclear image and was not able to identified cancer. That is to say, the prototype detector is able to reject Compton scattering events and inexpensive. Therefore, whole-body PET system with this detector must diagnose cancer with a diameter of 3 mm or more and be priced 1M$ or less. [ABSTRACT FROM AUTHOR]

COMPASS experiment, at CERN SPS, has been compiling for more than a decade successful and precise results on nucleon structure and hadron spectroscopy, leading to statistical errors much smaller than previously measured. The new COMPASS spin physics program, starting this year, aims to a rather complete nucleon structure description; this new representation goes beyond the collinear approximation by including the quark intrinsic transverse momentum distributions. The theoretical framework, for this new picture of the nucleon, is given by the Transverse Momentum Dependent distributions (TMDs) and by the Generalised Parton Distributions (GPDs). The TMDs, in particular Sivers, Boer-Mulders, pretzelosity and transversity functions will be obtained through the polarised Drell-Yan process, for the first time. The results will be complementary to those already obtained via polarised Semi-Inclusive Deep Inelastic Scattering (SIDIS). Also unpolarised SIDIS will be studied, allowing the knowledge improvement of the strange quark PDF and the access to the kaon fragmentation functions (FFs). Deeply Virtual Compton Scattering (DVCS) off an unpolarised hydrogen target will be used to study the GPDs, in a kinematic region not yet covered by any existing experiment. [ABSTRACT FROM AUTHOR]

The recently developed formalism of Generalized Parton Distributions (GPDs) allows connecting the experimental information of hard exclusive reactions to the spin contribution and even to the angular momentum contribution of quarks in the nucleon. By selecting different quantum numbers of the final state in exclusive productions, different GPDs can be addressed separately. The HERMES experiment at the HERA ring at DESY (Hamburg) made pioneering contributions and first constraints to Generalized Parton Distributions (GPDs), using hard exclusive vector meson production (EVMP) and Deeply Virtual Compton Scattering (DVCS). Using a novel recoil detector, HERMES managed to measure DVCS and EVMP free of any significant background. Selected results are highlighted and discussed in this paper. [ABSTRACT FROM AUTHOR]

Deeply virtual exclusive reactions provide a unique opportunity to probe the complex internal structure of the nucleon. They allow to access information about the correlations between parton transverse spatial and longitudinal momentum distributions from experimental observables. Dedicated experiments to study Deeply Virtual Compton Scattering (DVCS) and Deeply Virtual Meson Production (DVMP) have been carried out at Jefferson Lab using continuous electron beam with energies up to 6 GeV. Unpolarized cross sections, beam, target and double spin asymmetries have been measured for DVCS as well as for п0 exclusive electroproduction. The data from Hall B provide a wide kinematic coverage with Q²=1-4.5 GeV², xB=0.1-0.5, and -- t up to 2 GeV². Hall A data have limited kinematic range partially overlapping with Hall B kinematics but provide a high accuracy measurements. Scaling tests of the DVCS cross sections provide solid evidence of twist-2 dominance, which makes chiral-even GPDs accessible even at modest Q². We will discuss the interpretation of these data in terms of Generalized Parton Distributions (GPDs) model. Successful description of the recent CLAS п0 exclusive production data within the framework of the GPD-based model provides a unique opportunity to access the chiral-odd GPDs. [ABSTRACT FROM AUTHOR]

A selection of hard exclusive measurements (deeply virtual Compton Scattering and meson production) from past, present and future experimental programs are reviewed. The goal is the determination of the Generalized Parton Distributions which offer one of the most complete description of the partonic structure of the nucleon. [ABSTRACT FROM AUTHOR]

The analysis of exclusive meson leptoproduction (DVMP) within the handbag approach is reviewed and the parametrization of the generalized parton distributions (GPDs) is discussed in some detail with the main interest focused of the GPDs H and E. Applications of the GPDs extracted from DVMP to other hard exclusive processes as for instance deeply virtual Compton scattering (DVCS) and an evaluation of Ji's sum rule are also presented. [ABSTRACT FROM AUTHOR]

It has been recently proposed to study coherent deeply virtual Compton scattering (DVCS) off ³He nuclei to access neutron generalized parton distributions (GPDs). In particular, it has been shown that, in Impulse Approximation (IA) and at low momentum transfer, the sum of the quark helicity conserving GPDs of ³He, H and E, is dominated by the neutron contribution. This peculiar result makes the ³He target very promising to access the neutron information. We present here the IA calculation of the spin dependent GPD H of ³He. Also for this quantity the neutron contribution is found to be the dominant one, at low momentum transfer. The known forward limit of the IA calculation of H, yielding the polarized parton distributions of ³He, is correctly recovered. The extraction of the neutron information could be anyway non trivial, so that a procedure, able to take into account the nuclear effects encoded in the IA analysis, is proposed. These calculations, essential for the evaluation of the coherent DVCS cross section asymmetries, which depend on the GPDs H,E and H, represent a crucial step for planning possible experiments at Jefferson Lab. [ABSTRACT FROM AUTHOR]

In the present work, preliminary results of the analysis of polarization transfers in real Compton scattering (RCS) performed in Hall-C at JLAB are presented, for data collected at large scattering angle (θcm=70°) in the experiment E07-002. A previous experiment, E99-114, has already demonstrated a complete inconsistence of its results with a pQCD mechanism at JLAB energy regime. This kind of experiment, therefore, is of crucial importance for understanding the nature of the reaction mechanism for such a simple process, involving a real photon. Furthermore, RCS experiments allow the extraction of Compton form factors and Generalized Parton Distributions (GPDs), the latter connected to the total angular momentum of the nucleon. [ABSTRACT FROM AUTHOR]

Recent promising results, obtained at Jefferson Lab, on cross sections and asymmetries for DVCS and their link to the Generalized Parton Distributions are the focus of this paper. The extensive experimental program to measure DVCS with the 12-GeV-upgraded CEBAF in three experimental Halls (A, B, C) of Jefferson Lab, will also be presented. [ABSTRACT FROM AUTHOR]