Publications

Order by: publication date number of citations

• Probing quantum entanglement and collectivity effects in e+p collisions at HERA H1

  Chuan Sun

  SciPost Phys. Proc. 8, 147 (2022) · published 14 July 2022 | Toggle abstract · pdf

  Charged particle multiplicity spectra are measured at HERA H1 in DIS process at 319 GeV. The hadron entropy determined from the multiplicity spectra is compared to the gluon entropy predicted from a quantum-entanglement model. On the other hand, observed collective behaviours in high multiplicity pA, pp and ultra-peripheral PbPb collisions at RHIC and LHC motivate a study in ep collisions. Two- and multi-particle correlations are studied in DIS, as well as photoproduction events with collision energy <Wγp>~270 GeV.

• Transverse spin asymmetries for inclusive $\rho^0$ production in SIDIS at COMPASS

  A. Kerbizi

  SciPost Phys. Proc. 8, 146 (2022) · published 14 July 2022 | Toggle abstract · pdf

  The production of vector mesons in SIDIS is a particularly interesting channel to study the polarized fragmentation and related phenomena. Preliminary COMPASS results for the first measurement of inclusive $\rho^0$ Collins and Sivers transverse-spin asymmetries are presented here for the first time. The analysis is based on the data-set collected by COMPASS in $2010$ using a $160\, \rm{GeV}/c$ $\mu^+$ beam and a transversely polarized $NH_3$ target. The asymmetries are extracted as function of Bjorken-$x$, of the total transverse momentum of the oppositely charged hadron pair and of the fraction of available energy $z$ carried by the pair. Indications for positive Collins and Sivers asymmetries are obtained as expected from models.

• Photoproduction of diffractive dijets in Pythia 8

  Ilkka Helenius

  SciPost Phys. Proc. 8, 145 (2022) · published 14 July 2022 | Toggle abstract · pdf

  The new framework for the simulations of hard diffractive events in photoproduction within Pythia 8 is presented. The model, originally introduced for proton-proton collisions, applies the dynamical rapidity gap survival probability based on the multiparton interaction model in Pythia. These additional interactions provide a natural explanation for the observed factorization-breaking effects in hard diffraction by filling up the rapidity gaps used to classify the events of diffractive origin. The generated cross sections are well in line with the existing data from HERA experiments and predictions for the future electron-ion collider are presented. In addition, also predictions for ultra-peripheral collisions at the LHC have been calculated where the factorization-breaking effects are found to be more pronounced.

• TMD observables in unpolarised Semi-Inclusive DIS at COMPASS

  Andrea Moretti

  SciPost Phys. Proc. 8, 144 (2022) · published 14 July 2022 | Toggle abstract · pdf

  In 2016 and 2017, the COMPASS Collaboration at CERN collected a large sample of DIS events with a longitudinally polarised 160 GeV/$c$ muon beam scattering off a liquid hydrogen target. Part of the collected data has been analysed to extract preliminary results for the amplitudes of the modulations in the azimuthal angle of the charged hadrons and for their transverse-momentum distributions. These observables give relevant information for the study of the transverse momentum and spin structure of the nucleon. Similarly to the results obtained in COMPASS with a deuteron target, the azimuthal asymmetries exhibit interesting kinematic dependences, while the squared-transverse-momentum distributions can be described by two exponentials.

• QCD factorization for hadronic quarkonium production at high $p_T$

  Kyle Lee, Jian-Wei Qiu, George Sterman, Kazuhiro Watanabe

  SciPost Phys. Proc. 8, 143 (2022) · published 14 July 2022 | Toggle abstract · pdf

  Heavy quarkonium production at high transverse momentum ($p_T$) in hadronic collisions is explored in the QCD factorization approach. We find that the leading power in the $1/p_T$ expansion is responsible for high $p_T$ regime, while the next-to-leading power contribution is necessary for the low $p_T$ region. We present the first numerical analysis of the scale evolution of coupled twist-2 and twist-4 fragmentation functions (FFs) for heavy quarkonium production and demonstrate that the QCD factorization approach is capable of describing the $p_T$ spectrum of hadronic $J/\psi$ production at the LHC.

  4 citations

• Prospects for diffractive dijet photoproduction at the EIC

  V. Guzey, M. Klasen

  SciPost Phys. Proc. 8, 142 (2022) · published 14 July 2022 | Toggle abstract · pdf

  We discuss the prospects of diffractive dijet photoproduction at the EIC to distinguish different fits of diffractive proton PDFs, different schemes of factorization breaking, to determine diffractive nuclear PDFs and pion PDFs from leading neutron production.

• Inclusive and diffractive dijet photoproduction in ultraperipheral heavy ion collisions at the LHC

  V. Guzey, M. Klasen

  SciPost Phys. Proc. 8, 141 (2022) · published 14 July 2022 | Toggle abstract · pdf

  We calculate the cross section of inclusive dijet photoproduction in ultraperipheral collisions (UPCs) of heavy ions at the CERN Large Hadron Collider using next-to-leading order perturbative QCD and demonstrate that it provides a good description of the ATLAS data. We study the role of this data in constraining nuclear parton distribution functions (nPDFs) using the Bayesian reweighting technique and find that it can reduce current uncertainties of nPDFs at small $x$ by a factor of 2. We also make predictions for diffractive dijet photoproduction in UPCs and examine its potential to shed light on the disputed mechanism of QCD factorization breaking in diffraction.

• Measurements of $W$ and $Z/γ^*$ cross sections and their ratios in $pp$ collisions at STAR

  Jae Nam

  SciPost Phys. Proc. 8, 140 (2022) · published 14 July 2022 | Toggle abstract · pdf

  While the unpolarized parton distribution functions of the valence quarks ($d$ and $u$) are well determined from DIS experiments, the sea quark counterparts, $\bar{d}$ and $\bar{u}$, are much less constrained, in particular, near the valence region. Measurements of $W^+/W^-$ production ratio in $pp$ collider experiments, such as the STAR experiment at RHIC, can probe the $\bar{d}/\bar{u}$ ratio at a large $Q^2$ set by the $W$ mass. These proceedings will discuss recent results of $W$ and $Z$ cross-section measurements using the STAR $pp$ collision data at a center-of-mass energy of $\sqrt{s} = 500/510\;\mathrm{GeV}$ collected in 2011, 2012, 2013 and 2017.

• Phenomenological extraction of a universal TMD fragmentation function from single hadron production in $e^+ e^-$ annihilations

  M. Boglione, J.O. Gonzalez-Hernandez, A. Simonelli

  SciPost Phys. Proc. 8, 139 (2022) · published 14 July 2022 | Toggle abstract · pdf

  Factorizing the cross section for single hadron production in $e^+e^-$ annihilations, differential in $z_h$, $P_T$ and thrust, is a highly non trivial task. We have devised a factorization scheme that allows us to recast the $e^+e^- \to hX$ cross section in the convolution of a calculable hard coefficient and a universal Transverse Momentum Dependent (TMD) Fragmentation Function (FF). The predictions obtained from our NLO-LL perturbative computation, together with a simple ansatz to model the non-perturbative part of the TMD, are applied to the experimental measurements of the BELLE Collaboration for the phenomenological extraction of this process independent TMD FF.

  2 citations

• Comparison of $pp$ and $p \bar{p}$ differential elastic cross sections and observation of the exchange of a colorless $C$-odd gluonic compound

  C. Royon

  SciPost Phys. Proc. 8, 138 (2022) · published 14 July 2022 | Toggle abstract · pdf

  We describe the discovery of the colorless $C$-odd gluonic compound, the odderon, by the D0 and TOTEM Collaborations by comparing elastic differential cross sections in $pp$ and $p \bar{p}$ interactions at high energies.