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In this work, we have established the relations between the T-even proton transverse-momentum-dependent parton distributions (TMDs) at all twist levels up to twist-4 using the light-front quark–diquark model. From the parameterization equations of TMDs, we have found that there are multiple ways by which a particular TMD can be expressed in terms of the initial and final helicity states of the proton. For the first time, we have presented a parameterization table that can be applied to the derivation and recognition of proton TMDs based on their helicity. We have constructed the linear and quadratic relationships of TMDs at the intra- and intertwist levels within the same model. We have also looked at the inequality relations that TMDs follow. Additionally, to provide easy access to the calculations, amplitude matrices have been expressed in the form of TMDs over all the possible helicities of the diquark. [ABSTRACT FROM AUTHOR]

The amount of irradiance incident on a photovoltaic module and the module temperature are essential parameters to estimate its performance and forecast its energy output. These data are often available only where there are meteorological stations. Consequently, other methods are required to estimate these data. The objective of this work was to estimate the irradiance and temperature from different models and further estimate the annual energy output for Bambili, Cameroon. To this effect, mathematical models such as Angstrom–Prescott (A‐P), Kaplanis, Duffie and Beckman, and Collares‐Pereira and Rabl were employed for the estimation of irradiance, while the WAVE, SOYGRO, and Parton and Logan models were used for temperature computations. Collares‐Pereira and Rabl irradiance models showed a lower percentage root mean square error (RMSE) value of 6.71 with respect to the National Aeronautics and Space Administration (NASA), while for temperature models, Parton and Logan performed better from 6 a.m. to noon and SOYGRO from 1 to 6 p.m. with percentage RMSE values of 7.17 and 9.86, respectively. With the estimated irradiance and temperatures from the models, the monthly and annual energy outputs were computed using mathematical models of the PV module. The percentage RMSE of the annual energy estimated with respect to the Photovoltaic Geographical Information System (PVGIS) was found to be 1.95 and 4.40 for BP3125 and BP3180 modules, respectively, while the percentage RMSE of the annual energy estimated with respect to Photovoltaic Software (PVsyst) was found to be 2.14 and 4.22 for BP3125 and BP3180 modules, respectively. In conclusion, the results showed that Collares‐Pereira and Rabl, SOYGRO, and PV model equations can be employed with BP3125 and BP3180 PV modules for the estimation of energy output for Bambili and other locations with no meteorological stations or internet services. [ABSTRACT FROM AUTHOR]

This paper presents a measurement of the production cross-section of a Z boson in association with b- or c-jets, in proton–proton collisions at s = 13 TeV with the ATLAS experiment at the Large Hadron Collider using data corresponding to an integrated luminosity of 140 fb - 1 . Inclusive and differential cross-sections are measured for events containing a Z boson decaying into electrons or muons and produced in association with at least one b-jet, at least one c-jet, or at least two b-jets with transverse momentum p T > 20 GeV and rapidity | y | < 2.5 . Predictions from several Monte Carlo generators based on next-to-leading-order matrix elements interfaced with a parton-shower simulation, with different choices of flavour schemes for initial-state partons, are compared with the measured cross-sections. The results are also compared with novel predictions, based on infrared and collinear safe jet flavour dressing algorithms. Selected Z + ≥ 1 c -jet observables, optimized for sensitivity to intrinsic-charm, are compared with benchmark models with different intrinsic-charm fractions. [ABSTRACT FROM AUTHOR]

The production of polarized mesons at the NICA (Nuclotron based Ion Collider fAcility) energy of GeV is studied on the basis of the generalized parton model in the leading order of perturbative QCD. The hadronization of a quark pair to a meson is described within the model of nonrelativistic QCD. Nonperturbative model parameters are determined on the basis of a comparison with available experimental data on the production of prompt mesons at the energies of GeV (NA3) and GeV (PHENIX). [ABSTRACT FROM AUTHOR]

Interest in studying multiparticle-production processes in lepton and hadron interactions has not faded to date. The development of strong-interaction theory in the form of quantum chromodynamics (QCD) permits describing these interactions at the level of quarks and gluons. The transition from partons to observed hadrons at the hadronization stage is very difficult. The gluon-dominance model describing multiparticle production of secondaries and including the hadronization stage is proposed in the present study. This model is applied to describing electron–positron annihilation. It confirms an active role of the gluon component in the formation of secondaries, is indicative of the fragmentation mechanism of hadronization occurring in a vacuum, and describes experimental data on multiplicity distributions. [ABSTRACT FROM AUTHOR]

A novel observable, the double nuclear modification factor, is proposed to probe simultaneously the initial and final state effects in nucleus–nucleus collisions. An interesting competition between the combinatorial enhancement in the double parton scattering and the suppression due to parton energy loss can be observed in the production rate of two hard particles. In particular, the production of mesons in association with a W boson is not suppressed but is enhanced in the region of moderate transverse momenta, unlike the case of unassociated (inclusive) production. At the same time, in the region of high enough transverse momenta the nuclear modification factor for associated production converges to that of unassociated . [ABSTRACT FROM AUTHOR]

We investigate the leading twist generalized transverse momentum dependent parton distributions (GTMDs) of the unpolarized and longitudinally polarized gluons in the nucleon. We adopt a light-front gluon-triquark model for the nucleon motivated by soft-wall AdS/QCD. The gluon GTMDs are defined through the off-forward gluon-gluon generalized correlator and are expressed as the overlap of light-cone wave functions. The GTMDs can be employed to provide the generalized parton distributions (GPDs) by integrating out the transverse momentum. The Fourier transform of the GPDs encodes the parton distributions in the transverse position space, namely, the impact parameter dependent parton distributions (IPDs). We also calculate the three gluon IPDs corresponding to the GPDs H g , E g and H ~ g , and present their dependence on x and b ⊥ , respectively. [ABSTRACT FROM AUTHOR]

We present an analytic calculation of the one-loop correction to the double-real emission contribution to the zero-jettiness soft function at N3LO in QCD, accounting for both gluon-gluon and quark-antiquark soft final-state partons. We explain all the relevant steps of the computation including the reduction of phase-space integrals to master integrals in the presence of Heaviside functions, and the methods we employed to compute them. [ABSTRACT FROM AUTHOR]

We study double parton distributions with flavor interference in the nucleon and compare them with previous results for the flavor diagonal case. We investigate both unpolarized and polarized partons. We compare our lattice results with those obtained from the simple description of the proton in terms of an SU(6) symmetric three-quark wave function and find that this description fails for both flavor and polarization dependence. We also derive and test a factorization ansatz for the unpolarized flavor interference distribution in terms of single-parton distributions and find that this ansatz fails to a large extent. [ABSTRACT FROM AUTHOR]

Lattice QCD offers the possibility of computing parton distributions from first principles, although not in the usual MS ¯ factorization scheme. Calculations are therefore matched to MS ¯ using a perturbative procedure which is the source of significant uncertainty within the currently accessible kinematics. We present the possibility of computing the z2 evolution of non-singlet pseudo-parton distribution functions within the short factorization scheme in a numerically improvable way. The goal is to have tools to evolve a calculation to a scale where perturbative uncertainties are less pronounced. We compare a numerical extraction of the evolution operator from lattice data to the computation of z2 dependence in perturbation theory. Finally, we discuss how this numerical work may be extended to address the two-scale problem that arises when the Ioffe time range must be made large to extend the reach of the calculation of the pseudo-PDF to smaller values of the momentum fraction. [ABSTRACT FROM AUTHOR]

Measurements of quarkonia isolation in jets at the Large Hadron Collider (LHC) have been shown to disagree with fixed-order non-relativistic quantum chromodynamics (NRQCD) calculations, even at higher orders. Calculations using the fragmenting jet function formalism are able to better describe data but cannot provide full event-level predictions. In this work we provide an alternative model via NRQCD production of quarkonia in a timelike parton shower. We include this model in the Pythia 8 event generator and validate our parton-shower implementation against analytic forms of the relevant fragmentation functions. Finally, we make inclusive predictions of quarkonia production for the decay of the standard-model Higgs boson. [ABSTRACT FROM AUTHOR]

The production of a W-boson with a charm quark jet provides a highly sensitive probe of the strange quark distribution in the proton. Employing a novel flavour dressing procedure to define charm quark jets, we compute W+charm-jet production up to next-to-next-to-leading order (NNLO) in QCD. We study the perturbative stability of production cross sections with same-sign and opposite-sign charge combinations for the W boson and the charm jet. A detailed breakdown according to different partonic initial states allows us to identify particularly suitable observables for the study of the quark parton distributions of different flavours. [ABSTRACT FROM AUTHOR]

We cure the perturbative instability of the total-inclusive-photoproduction cross sections of vector S-wave quarkonia observed at high photon-proton-collision energies ( s γ p ) in Next-to-Leading Order (NLO) Collinear-Factorisation (CF) computations. This is achieved using High-Energy Factorisation (HEF) in the Doubly-Logarithmic Approximation (DLA), which is a subset of the Leading-Logarithmic Approximation (LLA) of HEF which resums higher-order QCD corrections proportional to α s n ln n - 1 (s ^ / M 2) in the Regge limit s ^ ≫ M 2 with M 2 being the quarkonium mass and s ^ is the squared partonic-center-of-mass energy. Such a DLA is strictly consistent with the NLO and NNLO DGLAP evolutions of the parton distribution functions. By improving the treatment of the large- s ^ asymptotics of the CF coefficient function, the resummation cures the unphysical results of the NLO CF calculation. The matching is directly performed in s ^ space using the Inverse-Error Weighting matching procedure which avoids any possible double counting. The obtained cross sections are in good agreement with data. In addition, the scale-variation uncertainty of the matched result is significantly reduced compared to the LO results. Our calculations also yield closed-form analytic limits for s ^ ≫ M 2 of the NLO partonic CF and numerical limits for contributions to those at NNLO scaling like α s 2 ln (s ^ / M 2) . [ABSTRACT FROM AUTHOR]

We study the transverse momentum ( p T ) spectra of neutral pions and identified charged hadrons produced in proton–proton (pp), deuteron–gold (d–Au), and gold–gold (Au–Au) collisions at the center of mass energy s NN = 200 GeV. The study is made in the framework of a multisource thermal model used in the partonic level. It is assumed that the contribution to the p T -value of any hadron comes from two or three partons with an isotropic distribution of the azimuthal angle. The contribution of each parton to the p T -value of a given hadron is assumed to obey any one of the standard (Maxwell-Boltzmann, Fermi-Dirac, and Bose-Einstein) distributions with the kinetic freeze-out temperature and average transverse flow velocity. The p T spectra of the final-state hadrons can be fitted by the superposition of two or three components. The results obtained from our Monte Carlo method are used to fit the experimental results of the PHENIX and STAR Collaborations. The results of the present work serve as a suitable reference baseline for other experiments and simulation studies. [ABSTRACT FROM AUTHOR]

We study the azimuthal angle dependence of the energy-energy correlators in the back-to-back region for e+e− annihilation and deep inelastic scattering (DIS) processes with general polarization of the proton beam. We demonstrate that the polarization information of the beam and the underlying partons from the hard scattering is propagated into the azimuthal angle dependence of the energy-energy correlators. In the process, we define the Collins-type EEC jet functions and introduce a new EEC observable using the lab-frame angles in the DIS process. Furthermore, we extend our formalism to explore the two-point energy correlation between hadrons with different quantum numbers in the back-to-back limit . We find that in the Operator Product Expansion (OPE) region the nonperturbative information is entirely encapsulated by a single number. Using our formalism, we present several phenomenological studies that showcase how energy correlators can be used to probe transverse momentum dependent structures. [ABSTRACT FROM AUTHOR]

Monte Carlo event generators for hard hadronic collisions depend on the evolution of parton showers backwards from a high-scale subprocess to the hadronization scale. The evolution is treated as a branching process with a sequence of resolvable parton emissions. The criterion of resolvability involves cutoffs that determine the no-emission probability (NEP) for a given range of the evolution scale. Existing event generators neglect cutoff-dependent terms in the NEP that, although formally power-suppressed, can have significant phenomenological effects. We compute such terms and study their consequences. One important result is that it is not possible for the backward shower to faithfully reproduce the cutoff-independent parton distribution functions (PDFs) used to generate it. We show that the computed NEP corrections mitigate but do not eliminate this problem. An alternative approach is to use cutoff-dependent PDFs that are consistent with the uncorrected NEP. Then one must apply cutoff-dependent corrections to hard subprocess matrix elements. We compute those corrections to the first nontrivial order for the Drell-Yan process and for Higgs production by gluon fusion. [ABSTRACT FROM AUTHOR]

Understanding the production mechanism of exotic hadrons with the structures beyond naive parton model can be helpful to find out their inner configuration and also to check the theory of quantum chromodynamics (QCD). Theoretically, fragmentation is known as the dominant production mechanism of conventional heavy hadrons with large transverse momentum so as this mechanism can also be considered for heavy pentaquarks production. In the present work, we first study the fragmentation function of S-wave fully heavy pentaquarks in leading-order perturbative QCD and then we will estimate their production cross section in pair annihilation process at lowest order of perturbation theory, relevant for the present and future high energy electron–positron colliders. [ABSTRACT FROM AUTHOR]

We present a study of the internal structure of lowest-lying octet baryons using one-loop quantum fluctuations of a fermion state in Yukawa theory. Employing a quark-scalar diquark model, we compute the Generalized Parton Distributions (GPDs) for the various members of the octet baryon differing by their amount of strange content. Different possible combinations of quark-scalar diquark pairs have been considered. The quark helicity independent chiral even GPDs in momentum as well as impact parameter space have been studied for purely transverse momentum transfer (zero skewness). We have also extended our calculations to explore and visualize the distinct behavior of charge distributions in coordinate space as well as charge densities in impact parameter space. Furthermore, magnetization density in impact parameter space has also been investigated. Quantitative as well as qualitative analysis of all the distributions has been carried out. [ABSTRACT FROM AUTHOR]

The mean transverse momentum of produced particles, [ p T ] , and its event-by-event fluctuations give direct access to the initial conditions of ultra-relativistic heavy-ion collisions and help probe the colliding nuclei's structure. The [ p T ] fluctuations can be studied via multi-particle p T correlations; so far, only the lowest four orders have been studied. Higher-order fluctuations can provide stronger constraints on the initial conditions and improved sensitivity to the detailed nuclear structure; however, their direct implementation can be challenging and is still lacking. In this paper, we apply a generic recursive algorithm for the genuine multi-particle p T correlations, which enables the accurate study of higher-order [ p T ] fluctuations without heavy computational cost for the first time. With this algorithm, we will examine the power of multi-particle p T correlations through Monte Carlo model studies with different nuclear structures. The impact on the nuclear structure studies, including the nuclear deformation and triaxial structure, will be discussed. These results demonstrate the usefulness of multi-particle p T correlations for studying nuclear structure in high-energy nuclei collisions at RHIC and the LHC, which could serve as a complementary tool to existing low-energy nuclear structure studies. [ABSTRACT FROM AUTHOR]

We present a symmetry-preserving scheme to derive the pion and kaon generalized parton distributions (GPDs) in Euclidean space. The key to maintaining crucial symmetries under this approach is the treatment of the scattering amplitude, such that it contains both the traditional leading-order piece and the scalar/vector pole contributions automatically, the latter being necessary to ensure the soft-pion theorem. The GPD is extracted analytically via the uniqueness and definition of the Mellin moments and we find that it naturally matches the double distribution representation; consequently, the polynomiality condition and sum rules are satisfied. The present scheme thus paves the way for the extraction of the GPD in Euclidean space using the Dyson-Schwinger equation framework or similar continuum approaches. [ABSTRACT FROM AUTHOR]

In this work, we analyze nuclear effects in the inclusive production of quarkonium in proton‐nucleus collisions at high energy regime. A theoretical framework that includes initial state effects like nuclear shadowing and gluon density saturation is considered. Numerical results for nuclear modification factor, RpA(y)$$ {R}_{pA}(y) $$, as a function of meson rapidity in proton‐nucleus collisions are presented. The parameter‐free predictions are compared to the available data from the Large Hadron Collider. Discussion on the main theoretical uncertainties is made, with emphasis on the phenomenological models for the nuclear saturation scale. [ABSTRACT FROM AUTHOR]

We study the energy distribution of hard gluons traversing a dense quark‐gluon plasma by comparing various transverse momentum broadening rates q^(t)$$ \hat{q}(t) $$, using a probabilistic perturbative approach. These results were applied to address the thermalization problem in heavy ion collisions. Within the weak coupling model, thermalization follows a "bottom‐up" process: early‐formed high‐energy partons emit low‐energy gluons, leading to their equilibrium formation, creating a thermal bath that facilitates equilibrium in the high‐energy sector. Under this scenario, we model the time dependencies of q^(t)$$ \hat{q}(t) $$ as a power‐law q^(t)∼tn$$ \hat{q}(t)\sim {t}^n $$, and assess the impact of n$$ n $$ on the distribution of hard gluons passing through the medium. [ABSTRACT FROM AUTHOR]

We present the first complete simulation framework, in the event generator, for resolved photon interactions at next-to leading order accuracy. It includes photon spectra obtained through the equivalent-photon approximation, parton distribution functions to parametrize the hadronic structure of quasi-real photons, the matching of the parton shower to next-to leading order QCD calculations for resolved photon cross sections, and the modelling of multiple-parton interactions. We validate our framework against a wide range of photo-production data from and experiments, observing good overall agreement. We identify important future steps relevant for high-quality simulations at the planned Electron–Ion Collider. [ABSTRACT FROM AUTHOR]

We present a systematic study demonstrating the impact of lattice QCD data on the extraction of generalised parton distributions (GPDs). For this purpose, we use a previously developed modelling of GPDs based on machine learning techniques fulfilling the theoretical requirements of polynomiality, a form of positivity constraint and known reduction limits. A special care is given to estimate the uncertainty stemming from the ill-posed character of the connection between GPDs and the experimental processes usually considered to constrain them, like deeply virtual Compton scattering (DVCS). Moke lattice QCD data inputs are included in a Bayesian framework to a prior model based on an Artificial Neural Network. This prior model is fitted to reproduce the most experimentally accessible information of a phenomenological extraction by Goloskokov and Kroll. We highlight the impact of the precision, correlation and kinematic coverage of lattice data on GPD extraction at moderate ξ which has only been brushed in the literature so far, paving the way for a joint extraction of GPDs. [ABSTRACT FROM AUTHOR]

The Parton Branching (PB) method describes the evolution of transverse momentum dependent (TMD) parton distributions, covering all kinematic regions from small to large transverse momenta k T . The small k T -region is very sensitive both to the contribution of the intrinsic motion of partons (intrinsic k T ) and to the resummation of soft gluons taken into account by the PB TMD evolution equations. We study the role of soft-gluon emissions in TMD as well as integrated parton distributions. We perform a detailed investigation of the PB TMD methodology at next-to-leading order (NLO) in Drell–Yan (DY) production for low transverse momenta. We present the extraction of the nonperturbative "intrinsic- k T " distribution from recent measurements of DY transverse momentum distributions at the LHC across a wide range in DY masses, including a detailed treatment of statistical, correlated and uncorrelated uncertainties. We comment on the (in)dependence of intrinsic transverse momentum on DY mass and center-of-mass energy, and on the comparison with other approaches. [ABSTRACT FROM AUTHOR]

Light-front formulations of quantum field theories have many advantages for computing electroweak matrix elements of strongly interacting systems and other quantities that are used to study hadronic structure. The theory can be formulated in Hamiltonian form so non-perturbative calculations of the strongly interacting initial and final states are in principle reduced to linear algebra. These states are needed for calculating parton distribution functions and other types of distribution amplitudes that are used to understand the structure of hadrons. Light-front boosts are kinematic transformations so the strongly interacting states can be computed in any frame. This is useful for computing current matrix elements involving electroweak probes where the initial and final hadronic states are in different frames related by the momentum transferred by the probe. Finally in many calculations the vacuum is trivial so the calculations can be formulated in Fock space. The advantages of light front-field theory would not be interesting if the light-front formulation was not equivalent to the covariant or canonical formulations of quantum field theory. Many of the distinguishing properties of light-front quantum field theory are difficult to reconcile with canonical or covariant formulations of quantum field theory. This paper discusses the resolution of some of the apparent inconsistencies in canonical, covariant and light-front formulations of quantum field theory. The puzzles that will be discussed are (1) the problem of inequivalent representations (2) the problem of the trivial vacuum (3) the problem of ill-posed initial value problems (4) the problem of rotational covariance (5) the problem of zero modes and (6) the problem of spontaneously broken symmetries. [ABSTRACT FROM AUTHOR]

We introduce the parton cascade Alpaca, which evolves parton ensembles corresponding to single events according to the effective kinetic theory of QCD at high temperature formulated by Arnold, Moore and Yaffe by explicitly simulating elastic scattering, splitting and merging. By taking the ensemble average over many events the phase space density (as evolved by the Boltzmann equation) is recovered, but the parton cascade can go beyond the evolution of the mean because it can be turned into a complete event generator that produces fully exclusive final states including fluctuations and correlations. The parton cascade does not require the phase space density as input (except for the initial condition at the starting time). Rather, effective masses and temperature, which are functions of time and are defined as integrals over expressions involving the distribution function, are estimated in each event from just the parton ensemble of that event. We validate the framework by showing that ensembles sampled from a thermal distribution stay in thermal equilibrium even after running the simulation for a long time. This is a non-trivial result, because it requires all parts of the simulation to intertwine correctly. [ABSTRACT FROM AUTHOR]

The article discusses Stéphane Madelrieux's book "Expériences radicales et expériences enracinées," which explores the concept of radical experiences and rooted experiences. The author argues that these experiences have both physical-empirical and metaphysical value, and distinguishes between ordinary experiences, pure experiences, and limit experiences. The text examines the influence of philosophers like Nietzsche, William James, Bataille, and Foucault on the understanding of radical experiences, and questions whether Nietzsche was the first to identify their traits in Dionysian ecstasy. It also explores the relationship between the Dionysian and the Apollonian, and raises questions about the role of philosophy in understanding these experiences. The text concludes by proposing a pragmatic approach that views exceptional experiences as natural and embedded within ordinary experiences. [Extracted from the article]

In this paper, we study the associated production of prompt J / ψ mesons and Z (W) bosons in the improved color evaporation model using the high-energy factorization as it is formulated in the parton Reggeization approach. The last one is based on the modified Kimber–Martin–Ryskin–Watt model for unintegrated parton distribution functions and the effective field theory of Reggeized gluons and quarks, suggested by Lipatov. We predict cross-section for associated J / ψ and Z (W) hadroproduction via the single and double parton scattering mechanisms using the set of model parameters which has been obtained early for description of single and double prompt J / ψ production at the LHC energies. The numerical calculations are realized using the Monte Carlo event generator KaTie. The calculation results are compared with the data at the energies s = 7 TeV and 8 TeV and we make predictions for the energy s = 1 3 TeV for J / ψ plus Z (W) and ϒ plus Z (W) associated production at s = 8 TeV and 13 TeV. [ABSTRACT FROM AUTHOR]

We revisit the next-to-leading order (NLO) perturbative QCD corrections for the deeply virtual meson production (DVMP) process, exploring its phenomenology both in isolation and in a multichannel fit combined with deeply virtual Compton scattering (DVCS). Our approach involves the conformal partial wave (CPaW) formalism, which allows for the straightforward inclusion of higher-order contributions and evolutionary effects. Our findings indicate that a description of the longitudinal component of the vector meson DVMP cross-section at high energies is achievable only at NLO within the standard collinear approach. Furthermore, we demonstrate a simultaneous description of DIS, DVCS, and DVMP processes, providing insights into the proton structure described at NLO by unique universal generalized parton distribution (GPD) functions. [ABSTRACT FROM AUTHOR]

We elucidate the structure of the next-to-leading-power soft-gluon expansion of arbitrary one-loop massless-QCD amplitudes. The expansion is given in terms of universal colour-, spin- and flavour-dependent operators acting on process-dependent gauge-invariant amplitudes. The result is proven using the method of expansion-by-regions and tested numerically on non-trivial processes with up to six partons. In principle, collinear-region contributions are expressed in terms of convolutions of universal jet operators and process-dependent amplitudes with two collinear partons. However, we evaluate these convolutions exactly for arbitrary processes. This is achieved by deriving an expression for the next-to-leading power expansion of tree-level amplitudes in the collinear limit, which is a novel result as well. Compared to previous studies, our analysis, besides being more general, yields simpler formulae that avoid derivatives of process-dependent amplitudes in the collinear limit. [ABSTRACT FROM AUTHOR]

We compute the three-loop correction to the universal single-soft emission current for the case of scattering amplitudes with two additional color-charged partons. We present results valid for QCD and N = 4 super-symmetric Yang-Mills theory. To achieve our results we develop a new integrand expansion technique for scattering amplitudes in the presence of soft emissions. Furthermore, we obtain contributions from single final-state parton matrix elements to the Higgs boson and Drell-Yan production cross section at next-to-next-to-next-to-next-to leading order (N4LO) in perturbative QCD in the threshold limit. [ABSTRACT FROM AUTHOR]

In double parton scattering (DPS), two partonic collisions take place between one pair of colliding hadrons. The effect of DPS can be significant for precision measurements due to the additional radiation from secondary partonic collisions, and especially for specific processes such as same-sign WW production. Its effect is usually included through Monte Carlo parton showers. In a factorization approach to DPS, the initial state is described by double parton distributions (DPDs). These are currently poorly constrained by experiment, but provide a view on interesting correlations between partons in the hadron. Here we show that the Large Momentum Effective Theory approach can be applied to DPDs. Specifically, we present a general matching relation between DPDs and lattice-calculable quasi-DPDs for general flavor, spin and color structures. We furthermore calculate the one-loop matching coefficients for the quark-quark DPDs, verifying that the infrared logarithms and divergences cancel in the matching. While we restrict to the flavor-non-singlet case, we do take color and spin correlations into account. Interestingly, quasi-DPDs combines nontrivial features from both the collinear and transverse momentum dependent quasi-parton distribution functions. This represents a first step in extending the quasi-PDF approach to DPDs, opening up a new way to constrain these distributions using lattice QCD. [ABSTRACT FROM AUTHOR]

We use the AMPT model to simulate the shear viscous transport dynamics of parton matter for Pb + Pb collisions at 2760A GeV. The shear viscosity to entropy density ratio is parameterized as a function of temperature and the partonic phase temperature is calculated by the Gaussian smearing approximation of the parton energy density. The results of particle spectra and elliptic flow are compared with experimental data and show a reasonable agreement. The elliptic flow is found to be more sensitive to the shear viscosity than the particle spectra and more influenced by the temperature-dependent shear viscosity than the constant ratio at large transverse momentum and midrapidity regions. The final observables are influenced by the partonic system evolution process, which is reflected by the effect of temperature-dependent shear viscosity. [ABSTRACT FROM AUTHOR]