Publications

Order by: publication date number of citations

• Diffractive dissociation in future electron-ion colliders

  Anh Dung Le

  SciPost Phys. Proc. 8, 168 (2022) · published 14 July 2022 | Toggle abstract · pdf

  We study diffractive scattering cross sections, focusing on the rapidity gap distribution in realistic kinematics at future electron-ion colliders. Our study consists in numerical solutions of the QCD evolution equations in both fixed and running coupling frameworks. The fixed and the running coupling equations are shown to lead to different shapes for the rapidity gap distribution. The obtained distribution when the coupling is fixed exhibits a shape characteristic of a recently developed model for diffractive dissociation, which indicates the relevance of the study of that diffractive observable for the partonic-level understanding of diffraction.

• Latest ALICE results on J/$ψ$ photoproduction in ultra-peripheral collisions at the LHC

  Tomas Herman

  SciPost Phys. Proc. 8, 106 (2022) · published 13 July 2022 | Toggle abstract · pdf

  Ultra-peripheral collisions (UPCs), studied using the ALICE detector, allow us to investigate the low-$x$ behavior of the gluon distribution of the colliding particles. Two new measurements of coherent J/$\psi$ photoproduction cross section from Pb-Pb UPCs at $\sqrt{s_{\rm NN}}=5.02$ TeV are presented: the first measurement of the $|t|$-dependence of the cross section providing a new tool to investigate the transverse gluonic structure at low Bjorken-$x$ and a rapidity-differential measurement at midrapidity allowing us to provide stringent constraints on nuclear gluon shadowing and saturation models. In addition, prospects for heavy vector meson photoproduction measurements in LHC Run 3 and 4 are presented.

• Hadron Polarimetry for the Electron-Ion Collider

  A.S. Nunes, E.C. Aschenauer, O. Eyser, W. Schmidke

  SciPost Phys. Proc. 8, 163 (2022) · published 14 July 2022 | Toggle abstract · pdf

  The Electron-Ion Collider (EIC) will be the first collider to use both polarized electron beams and polarized proton and light ion beams. It will therefore offer unique opportunities to study the structure of nucleons and to answer fundamental questions in QCD. The uncertainties on the polarization measurement translate directly into the uncertainties of final physics observables. Hence, a precise measurement of the hadron beam polarization and a good control of systematic uncertainties are critical for the success of the spin program at the EIC. Contrary to the case of electron beam polarimetry, which uses physical processes derived from first principles that allow a high precision extraction of the electron beam polarization, for hadron beams no such process is available. The currently best used methods rely on the process of elastic scattering in the Coulomb-Nuclear Interference (CNI) region, for which there are only effective models available. The experience from RHIC, the only existing polarized proton collider, will be detailed and the challenges of the measurements at the EIC will be addressed. In particular, measurements of the present RHIC polarimeters and simulations of the future EIC polarimeters will be presented.

• Understanding the proton mass in QCD

  Andreas Metz, Barbara Pasquini, Simone Rodini

  SciPost Phys. Proc. 8, 105 (2022) · published 13 July 2022 | Toggle abstract · pdf

  Understanding the proton mass in quantum chromodynamics (QCD) is a very important and current topic in hadronic physics. The decomposition (sum rule) of the proton mass is not unique, and different sum rules, which are related to the QCD energy-momentum tensor, can be found in the literature. We review and compare these sum rules and identify open questions in this field.

• Gluon saturation in proton and its contribution to single inclusive soft gluon production in high energy proton-nucleus collisions

  Ming Li

  SciPost Phys. Proc. 8, 162 (2022) · published 14 July 2022 | Toggle abstract · pdf

  The leading order single inclusive soft gluon production in high energy proton-nucleus (pA) collisions has been studied by various approaches for more than two decades. The first correction due to the gluon saturation in proton was analytically attempted recently through a diagrammatic approach in which only partial results were obtained. An important feature of the first saturation correction is that it includes both initial state and final state interactions. In this paper, we present the complete result derived from the Color Glass Condensate framework. Our approach is to analytically solve the classical Yang-Mills equations in the dilute-dense regime and then use the Lehmann-Symanzik-Zimmermann (LSZ) reduction formula to obtain gluon production from classical gluon fields.

• Single-Logarithmic Corrections to Small-$x$ Helicity Evolution

  Yossathorn Tawabutr

  SciPost Phys. Proc. 8, 103 (2022) · published 13 July 2022 | Toggle abstract · pdf

  The small-$x$ quark helicity evolution equations at double-logarithmic order, with the kernel $\sim\alpha_s\ln^2(1/x)$, have been derived previously. In this work, we derive the single-logarithmic corrections to the equations, to order $\alpha_s\ln(1/x)$ of the evolution kernel. The new equations include the effects of the running coupling and the unpolarized small-$x$ evolution, both of which are parametrically significant at single-logarithmic order. The large-$N_c$ and large-$N_c\& N_f$ approximations to the equation are computed. (Here, $N_c$ and $N_f$ are the numbers of quark colors and flavors, respectively.) Their solutions will provide more precise estimates of the quark helicity distribution at small $x$, contributing to the resolution of the proton spin puzzle.

• Azimuthal correlations in diffractive scattering at the Electron-Ion Collider

  Adrian Dumitru, Heikki Mäntysaari, Risto Paatelainen, Kaushik Roy, Farid Salazar, Björn Schenke

  SciPost Phys. Proc. 8, 102 (2022) · published 13 July 2022 | Toggle abstract · pdf

  We calculate azimuthal correlations between the exclusively produced vector meson and the scattered electron in Deep Inelastic Scattering processes at the future Electron-Ion Collider (EIC). We identify "kinematical" and "intrinsic" contributions to these correlations, and show that the correlations are sensitive to the non-trivial correlations in the gluon distribution of the target. Realistic predictions at the EIC kinematics are provided using two different approaches to describe the dipole-proton interaction at relatively small $x$.