Publications

Order by: publication date number of citations

• Prompt hadroproduction of C-even quarkonia in the light-front $k_T$ -factorization approach

  Wolfgang Schäfer, Izabela Babiarz, Roman Pasechnik, Antoni Szczurek

  SciPost Phys. Proc. 8, 032 (2022) · published 11 July 2022 | Toggle abstract · pdf

  We present a new approach for the prompt production of quarkonia which is based on the $k_T$-factorization method. The production of even C-parity quarkonia proceeds via the fusion of two (off-shell) gluons. Especially in the kinematics of the LHCb experiment these processes are thus expected to be a sensitive probe of the small-x gluon distribution. We calculate the relevant off-shell matrix elements in terms of the light-front wave functions of the quarkonium states. We present our results for scalar and pseudoscalar charmonia and discuss photon transition form factors as well as cross sections for prompt hadroproduction. We compare our results for the $\eta_c$ to recent LHCb data.

• Resummation for $tqH$ production

  Matthew Forslund, Nikolaos Kidonakis

  SciPost Phys. Proc. 8, 021 (2022) · published 11 July 2022 | Toggle abstract · pdf

  We present results with soft-gluon resummation for the associated production of a single top quark and a Higgs boson. We present analytical results for the higher-order soft-gluon corrections and numerical results for the total cross section and top-quark transverse momentum and rapidity distributions at LHC energies.

• Measurements and searches of Higgs boson production involving fermion couplings with the ATLAS detector

  Shigeki Hirose

  SciPost Phys. Proc. 8, 006 (2022) · published 11 July 2022 | Toggle abstract · pdf

  In the standard model, fermions acquire the mass via the Yukawa interaction. This mechanism can be tested by measuring couplings of the fermions with the Higgs boson. At the ATLAS experiment, the Higgs-fermion coupling measurements became possible thanks to the abundant dataset: the integrated luminosity of 139~fb$^{-1}$ at the centre-of-mass energy of 13~TeV as well as 25~fb$^{-1}$ at 7--8~TeV. This paper presents recent results from measurements of the Higgs boson productions in decays to a fermion pair in the final state with the ATLAS detector.

• Spin Density Matrix Elements for Exclusive $\rho^{0}$ Meson Muoproduction at COMPASS

  W.~Augustyniak

  SciPost Phys. Proc. 8, 073 (2022) · published 12 July 2022 | Toggle abstract · pdf

  Spin density matrix elements were extracted from COMPASS data for exclusive $\rho^{0}$ meson muoproduction on a liquid hydrogen target. The measurement cover the kinematic range of 1.0 (GeV/$c$)$^2$ $< Q^{2} <$ 10.0 (GeV/$c$)$^2$, 5.0 GeV/$c^2$ $< W <$ 17.0 GeV/$c^2$ and 0.01 (GeV/$c$)$^2$ $<p^{2}_{T} < $ 0.5 (GeV/$c$)$^2$. Here, $W$ denotes the mass of the final hadronic system, $Q^{2}$ the virtuality of the exchanged photon and $p_{T}$ the transverse momentum of the $\rho^{0}$ meson with respect to the virtual-photon direction. We observe a violation of s-channel helicity conservation for the transition $\gamma^{*}_{T} \to \rho^{0}_{L}$. Additionally, we find a dominant contribution of the natural-parity-exchange transitions.

• The Belle II experiment: Status and prospects

  Kavita Lalwani (on behalf of the Belle II Collaboration)

  SciPost Phys. Proc. 8, 176 (2023) · published 11 July 2023 | Toggle abstract · pdf

  The Belle II experiment at the SuperKEKB energy asymmetric $e^{+}e^{-}$ collider is a substantial upgrade of the B factory facility at the Japanese KEK laboratory. The design luminosity of the machine is $6\times10^{35}$ $cm^{-2}s^{-1}$ and the Belle II experiment aims to record 50 $ab^{-1}$ of data, a factor of 50 more than its predecessor. With this data set, Belle II will be able to measure the Cabibbo-Kobayashi-Maskawa (CKM) matrix, the matrix elements and their phases, with unprecedented precision and explore flavor physics with $B$, charmed mesons, and $\tau$ leptons. Belle II has also a unique capability to search for low-mass dark matter and low-mass mediators. In this paper, we will review the status of the Belle II detector, SuperKEKB accelerator and the prospects for physics at Belle II.

• Probing gluon density fluctuations at large momentum transfer $|t|$ at HERA

  Arjun Kumar

  SciPost Phys. Proc. 8, 166 (2022) · published 14 July 2022 | Toggle abstract · pdf

  The information on the gluonic structure and its fluctuations is captured by the differential $|t|$ spectrum in diffractive events. The incoherent cross-section is sensitive to the fluctuations in the target wavefunction in such events. We investigate the incoherent $ep$ cross-section in $J/\psi$ photoproduction using the impact-parameter dependent dipole model. The spatial gluonic structure is modelled as hotspots of gluon density having substructure where this substructure is modelled as hotspots within hotspots. We find that three levels of the substructure provide a good description of all the data, available up to $|t|=30~$GeV$^2$. We investigate these fluctuations in both the saturated and non-saturated dipole models and compare our predictions with the HERA Data.

• 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.

• 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.

• 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.

• Simultaneous Extraction of Unpolarized PDFs and Nuclear Effects

  C. Cocuzza, A. Metz, N. Sato

  SciPost Phys. Proc. 8, 098 (2022) · published 13 July 2022 | Toggle abstract · pdf

  We present a new global QCD analysis of unpolarized parton distribution functions (PDFs) and nuclear effects including for the first time data from the SeaQuest and MARATHON experiments in addition to high-energy weak-boson-production data from the Tevatron and Large Hadron Collider. Simultaneously extracting the PDFs and nuclear effects, we examine the impact of the SeaQuest and MARATHON data on the light-quark sea asymmetry and the EMC ratios of deuterium, helium, and tritium.