The determination of the quark and gluon structure of the proton is a central component of the precision phenomenology program at the Large Hadron Collider (LHC) as well of future hadron-hadron and lepton-hadron colliders. In this talk I review recent progress in the determination of the quark and gluon structure of the proton, with emphasis on the impact of new processes in the global PDF...
The Wigner and Husimi distributions have been proposed as phase space distributions of partons inside the nucleon. I discuss various aspects of these distribution including their experimental measurement, model calculations, applications to spin physics.
We discuss inclusive photon production to next-to-leading order accuracy in both p+A and e+A collisions within the color glass condensate framework of high energy QCD. For hadron-hadron collisions, we will present comparisons to data in p+p and p+A collisions. For e+A data, we will outline some advantages of our framework relative to extant NLO computations in the literature.
I will review recent progress in nucleon structure calculations on the lattice, focusing on results obtained from simulations with physical or near-physical quark mass values. In particular, results on moments of generalized parton distributions and the axial, scalar, and tensor charges will be presented. I will also discuss the implications of these results on the decomposition of the nucleon...
Improvements in our understanding of confinement allows the modification of the phenomenology of jet fragmentation. Transverse-momentum dependent jet observables allow for a global description of the dynamics of QCD jets including long-range correlations associated with quantum interference.
I will first discuss entanglement entropy of
soft gluons in a light cone wave function of a fast moving projectile hadron and
then entropy production in collisions with target nucleus.
We develop a novel real-time approach to computing the entanglement between spatial regions for Gaussian states in quantum field theory. The entanglement entropy is characterized in terms of local correlation functions on space-like Cauchy hypersurfaces. The framework is applied to explore an expanding light cone geometry in the particular case of the Schwinger model for quantum...
Photoproduction in electron-proton collisions were extensively studied at HERA for several observables. In these processes a quasi-real photon from the lepton interacts with the proton. Due to the small virtuality, the photons may also fluctuate into a hadronic state so that constituting partons act as initiators of the hard process. The partonic structure of these resolved photons can be...
Thanks to A^{1/3} enhancement on the saturation scale in a heavy nucleus compared to that of the proton, nonlinearities are enhanced in nuclei compared to proton. This makes nuclear DIS an ideal laboratory to study the small-x structure of the nucleus. Probably the most powerful process for this is exclusive vector meson production, which at leading order is proportional to the squared gluon...
We calculate energy deposition and axial charge production from color flux tubes at early times in a heavy-ion collision. Based on analytic expressions for the space-time dependent fluctuations of the axial charge and energy density distributions in terms of the unpolarized and linearly polarized gluon distributions of the nuclei, we develop a phenomenological model for the initial state,...
I will describe the status of lattice QCD studies of gluon structure quantities in nucleons and nuclei. I will focus in particular on the prospects for controlled determinations of key effects such as a gluon analogue of the EMC effect, and exotic glue in nuclei, ahead of the planned EIC.
The correlation length associated with color-charge fluctuations, known as the inverse saturation momentum, plays a fundamental role in the initial conditions of heavy-ion collisions. With state-of-the-art hydrodynamic codes tailored for the finite-baryon-density physics of the Beam Energy Scan, it is interesting to study the analogous role of correlations between quarks and antiquarks. ...
The Electron-Ion Collider (EIC) will provide the first opportunity to study electron-nucleus (eA) scattering at high energies. For heavy ions, key measurements include QCD at high gluon densities and the onset of saturation, mapping of the transverse spatial gluon distribution through coherent diffraction, and parton/hadron propagation in cold nuclear matter. All these measurements greatly...
We study the color coherence phenomenon starting from the original quark-antiquark antenna laboratory in the presence of a medium. Measurements of jet substructure shed light on the character of the jet interactions with the dense medium formed in the collisions, which can break the intrajet color coherence leading to interesting phenomena. Describing the decoherence of the $ q \bar{q} $ pair...
Within the Colour Glass Condensate effective field theory, the JIMWLK equation can also be used to describe the energy evolution of long-range rapidity correlations in nuclear collisions. The projectile interaction with the target classical field is described by Wilson lines. It is useful for numerical implementations to study JIMWLK evolution as a stochastic process. A Langevin equation then...
We report on the status of a current project by the RQCD lattice QCD group aimed at non-perturbatively estimating the second moment of the pion distribution amplitude. Our investigation is carried out using Nf=2+1 dynamical non-perturbatively order a improved Wilson fermions on lattices of different volumes and pion masses down to 220 MeV. We employ momentum smearing in order to decrease the...
During the last decade a robust TMD program has blossomed at RHIC. A variety of observables, including $W^{\pm}/Z$ and hadron+jet reconstruction, are sensitive to TMD parton distribution and fragmentation functions. This talk will review existing results, outline plans for continued studies in proton-proton collisions and discuss the implications for a future EIC.
We review the theory of transverse momentum distributions (TMDs). The emphasis is made on the recent development in the perturbation theory and its influence on the predictions/extraction of TMDs.
Nucleon TMDs from Lattice QCD
We summarize the calculation of the SIvers, Boer-Mulders, generalized transversity and worm-gear shifts using two ensembles of gauge configurations with different discretization of the fermion Dirac actions. We discuss factorization and renormalization of the operators and present estimates of lattice discretization artifacts. For these TMD observables, we find...
The feasibility of extracting information on gluon Transverse-Momentum Dependent (TMD) parton distributions, in particular the distribution of linearly polarized gluons, is discussed for the production of quarkonium pairs in proton collisions. Evidences are presented that azimuthal modulations of the cross section, caused by linearly polarized gluons, may be larger for a quarkonium pair in the...
Higher-twist transverse-momentum dependent parton distributions (TMDs) go beyond the parton model description of a proton as they describe correlations between quarks and gluons. Higher-twist TMDs, however, turn out to be very elusive objects, as they are difficult to extract from experimental data. Twist-3 distributions can be decomposed as a sum of different contributions. In general, these...
I will present the theoretical computation methods and several results for exclusive diffractive impact factors at NLO accuracy at small x with saturation, with an emphasis on corrections to light vector meson electroproduction on a dense target. I will discuss the practical use of our results for phenomenological predictions at an Electron-Ion Collider, as well as theoretical questions on...
Abstract:
Low-$x$ evolution of spin-dependent TMDs and spin $g_1$ structure function are relevant for the future Electron Ion Collider.
Recently, the spin-low-$x$ evolution was obtained in the saturation formalism. Unfortunately, it does not agree with previous result obtained by calculation of perturbative diagrams in the leading log approximation so an independent study on this subject...
After a brief reminder about the role of GPDs in the description of hadron structure, I will review what is known about these functions after a decade and a half of experiments and fits to the data, with emphasis on deeply virtual Compton scattering. I will show results of global fits, both in the traditional and in the neural network approach. I will also discuss main challenges for...
I will present an analysis of the parton transverse momentum, k_T, substructure of the generalized Wandzura Wilczek relations involving twist three Generalized Parton Distributions. Out of 16 possible Equation of Motion relations that can be written in the T-even sector, I will focus on three helicity configurations that can be detected analyzing specific spin asymmetries: two correspond to...
Our knowledge of nuclear Parton Distribution Functions is currently limited by the restricted kinematic space covered in fixed target $e+A$ experiments and $p(d)+A$ collisions. In this talk I will present an impact study of the possibilities offered by an Electron-Ion Collider for the improvement of the understanding of collinear factorized nuclear PDFs.
We provide a first calculation of the complete next-to-leading order QCD corrections for heavy flavor contributions to the inclusive structure function $g_1$ in longitudinally polarized deep-inelastic scattering. The results are derived with largely analytical methods and retain the full dependence on the heavy quark's mass. We discuss all relevant technical details of the calculation and...
We study quantitatively [1] the importance of the recently derived NLO corrections [2,3,4] to the DIS structure functions at small x in the dipole formalism. We show that these corrections can be significant and depend on the factorization scheme used to resum large logarithms of energy into renormalization group evolution with the BK equation. This feature is similar to what has recently been...
