Spain

Néstor Armesto

Miguel Ángel Escobedo

Elena G. Ferreiro

Víctor López-Pardo

Corrigendum to “A potential approach to the <italic>X</italic>(3872) thermal behavior&#8221; [Phys. Lett. B 854 (2024) 138760]

The assumption of factorization lies at the core of calculations of medium effects on observables computable in perturbative Quantum Chromodynamics. In this work we examine this assumption, for which we propose a setup to study hard processes and bulk nuclear matter in heavy-ion collisions on the same footing using the Glauber modelling of heavy nuclei. To exemplify this approach, we calculate the leading-order corrections to azimuthal decorrelation in Drell-Yan and boson-jet processes due to cold nuclear matter effects, not considering radiation. At leading order in both the hard momentum scale and the nuclear size, the impact-parameter dependent cross section is found to factorize for both processes. The factorization formula involves a convolution of the hard cross section with the medium-modified parton distributions, and, for boson-jet production, the medium-modified jet function.

Florian Cougoulic

Bin Wu

Cold nuclear matter effects on azimuthal decorrelation in heavy-ion collisions

We investigate the determination of the partonic structure of colorless exchanges in deep inelastic diffractive <math><mi>e</mi><mi>p</mi></math> scattering at the Electron Ion Collider (EIC), using the standard decomposition into Pomeron and Reggeon contributions. We perform fits to simulated diffractive cross section pseudodata in four variables, including the momentum transfer <math><mi>t</mi></math>, to estimate the achievable precision on the Pomeron and Reggeon quark and gluon distributions. We analyze the influence of different cuts in the kinematic variables, beam energy configurations, and luminosities, including a “first year” scenario. We conclude that the EIC will be able to constrain the partonic structure of the subleading Reggeon exchange with a precision comparable to that of the leading Pomeron exchange.

United Kingdom

Paul R. Newman

Poland

Wojciech Słomiński

United States

Anna M. Staśto

Extracting the partonic structure of colorless exchanges at the Electron Ion Collider

We analyze the effects of next-to-eikonal corrections on dijet production in Deep Inelastic Scattering off nuclear targets in the framework of the Color Glass Condensate. They require the knowledge of correlators of fields in the target beyond those computed in the standard McLerran-Venugopalan model, specifically those between transverse and boost-enhanced components, and of the recoil of the fields. We neglect the latter, while for the former we develop a linear model valid for large nuclei. We considered the unpolarized cross sections for dijet production in the approximation of a homogenous dilute nucleus, obtaining simple analytic expressions for the cross sections at next-to-eikonal accuracy, valid in the limit of total dijet momentum and dijet momentum imbalance larger than the saturation scale of the nucleus. We perform a numerical study of the results at energies of the Electron Ion Collider, finding   <math> <mi>O</mi> </math>  $$ \mathcal{O} $$ (10%) effects in the cross sections at large total momentum. We also analyze the azimuthal asymmetries between total momentum and imbalance, finding that non-eikonal corrections induce odd azimuthal harmonics for the situation of jets with equal momentum fractions from the virtual photon, where they are absent in the eikonal approximation. Finally, in the eikonal approximation we have compared the results of our analytic expansion valid in the dilute limit of the target, and the full Color Glass Condensate results in the McLerran-Venugopalan model and their correlation limit. Our analytic expressions match the correlation limit ones in the region where both should be simultaneously valid and reproduce very well the full Color Glass Condensate results in its validity region.

Pedro Agostini

Tolga Altinoluk

Next-to-eikonal corrections to dijet production in Deep Inelastic Scattering in the dilute limit of the Color Glass Condensate

We study the potential of <math><mi>X</mi><mo>(</mo><mn>3872</mn><mo>)</mo></math> at finite temperature in the Born-Oppenheimer approximation under the assumption that it is a tetraquark. We argue that, at large number of colors, it is a good approximation to assume that the potential consists in a real part plus a constant imaginary term. The real part is then computed adapting an approach by Rothkopf and Lafferty and using as input lattice QCD determinations of the potential for hybrids. This model allows us to qualitatively estimate at which temperature range the formation of a heavy tetraquark is possible, and to propose a qualitative picture for the dissociation of the state in a medium. Our approach can be applied to other suggested internal structures for the <math><mi>X</mi><mo>(</mo><mn>3872</mn><mo>)</mo></math> and to other exotic states.

A potential approach to the (3872) Thermal Behavior

A study is presented of the impact of updated simulated inclusive electron ion collider deep inelastic scattering data on the determination of the proton and nuclear parton distribution functions (PDFs) at next-to-next-to-leading and next-to-leading order in QCD, respectively. The influence on the proton PDFs is evaluated relative to the HERAPDF2.0 set, which uses inclusive HERA data only, and also relative to the global fitting approach of the MSHT20 PDFs. The impact on nuclear PDFs is assessed relative to the EPPS21 global fit and is presented in terms of nuclear modification ratios. For all cases studied, significant improvements in the PDF uncertainties are observed for several parton species. The most striking impact occurs for the nuclear PDFs in general and for the region of high Bjorken <math><mi>x</mi></math> in the proton PDFs, particularly for the valence quark distributions.

Germany

Thomas Cridge

CERN

Francesco Giuli

Lucian Harland-Lang

Paul Newman

Barak Schmookler

Robert Thorne

Katarzyna Wichmann

Impact of inclusive electron ion collider data on collinear parton distributions

We study the production, in deep inelastic scattering at high energy, of a quark-gluon dijet induced by <math><mi>t</mi></math>-channel quark exchange with the target, which goes beyond the eikonal approximation. Throughout this study we follow the color glass condensate approach, keep full dependence on the quark mass and consider the target to be unpolarized. We focus on the correlation limit in which the produced jets fly almost back-to-back and find a factorized expression for the cross section, for both longitudinal and transverse photons, involving the unpolarized quark transverse momentum dependent distribution. Quark-gluon dijets can be distinguished from other types of dijets at least in the heavy quark case, thanks to heavy flavor tagging. In that case, the dominant background is expected to come from the eikonal production of a quark-antiquark-gluon system. We propose experimental cuts to suppress that background contribution, making the process of quark-gluon dijet production in deep inelastic scattering a new method to probe the quark transverse momentum dependent distribution at the Electron Ion Collider.

Guillaume Beuf

Probing quark transverse momentum distributions in the color glass condensate: Quark-gluon dijets in deep inelastic scattering at next-to-eikonal accuracy

We revisit the calculation of the cross section for forward inclusive single hadron production in <math><mi>p</mi><mi>A</mi></math> collisions within the hybrid approach. We show that the proper framework to perform this calculation beyond leading order is not the collinear factorization, as has been assumed so far, but the transverse momentum dependent (TMD) factorized framework. Within the TMD factorized approach we show that all the large transverse logarithms appearing in the fixed order calculation are resummed into the evolution of the TMD parton distribution functions and TMD fragmentation functions with factorization scale. The resulting expressions, when written in terms of TMDs evolved to the appropriate, physically well understood factorization scale, contain no additional large logarithms. The absence of any large logarithms in the resummed result should ensure positivity of the cross section and eradicate the persistent problem that has plagued the previous attempts at calculating this observable in the hybrid approach.

Alexander Kovner

Israel

Michael Lublinsky

Single inclusive particle production at next-to-leading order in proton-nucleus collisions at forward rapidities: Hybrid approach meets TMD factorization

We perform a numerical analysis of the two particle azimuthal correlations at central rapidities generated in pA collisions within the framework of the Color Glass Condensate. We extend the standard computations to include the subeikonal corrections which stem from considering the finite longitudinal width of the dense target. For practical reasons, we only consider the next-to-next-to-eikonal corrections instead of using the all-order expressions for the inclusive two gluon production cross section. We show that the subeikonal terms that we account for in the two gluon yields contribute to both even and odd harmonics, the latter being absent in the standard Color Glass Condensate calculations performed at eikonal accuracy. Our analysis confirms the vanishing of the subeikonal effects with increasing collision energy and when going to forward rapidities, as expected.

Finite width effects on the azimuthal asymmetry in proton-nucleus collisions in the Color Glass Condensate

We study the effects on multigluon production at mid-rapidity in the Color Glass Condensate of the non-eikonal corrections that stem from relaxing the shockwave approximation and giving the target a finite size. We extend previous works performed in the dilute-dilute approximation suitable for proton–proton collisions, to the dilute-dense one applicable to proton–nucleus. We employ the McLerran–Venugopalan model for the projectile averages. For the target averages, we use the Golec-Biernat–Wüsthoff model and restrict to the leading contributions in overlap area that allow a factorization of ensembles of Wilson lines into products of dipoles. We make the connection with the jet quenching formalism and compare with previous results in the literature, providing a parametrization of the so-called decorated dipoles. We show that the non-eikonal effects on single inclusive particle production, contrary to what happens in jet quenching, are only sizable, of a few percent, for modest energies  $$\sqrt{s_{NN}}\le 100$$  <math> <mrow> <msqrt> <msub> <mi>s</mi> <mrow> <mi>NN</mi> </mrow> </msub> </msqrt> <mo>≤</mo> <mn>100</mn> </mrow> </math>   GeV and central rapidities. On the other hand, we find that the effects on double inclusive gluon production are larger for the same kinematics. We show that, as found previously in the dilute-dilute situation, non-eikonal corrections break the accidental symmetry in the CGC, allowing for the existence of non-vanishing odd azimuthal harmonics.

Fabio Dominguez

Portugal

José Milhano

Multiparticle production in proton–nucleus collisions beyond eikonal accuracy