Publications

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• First measurement of the forward rapidity gap distribution in pPb collisions at 8 TeV

  Dmitry E. Sosnov

  SciPost Phys. Proc. 8, 065 (2022) · published 12 July 2022 | Toggle abstract · pdf

  We present the forward rapidity gap spectra from proton-lead collisions for both I\!P-Pb and I\!P-p topologies measured at the CMS at a center-of-mass energy of 8.16 TeV. For the I\!P-Pb topology, the cross-section predicted by EPOS-LHC is a factor of two lower than the data while has reasonable description of the spectrum shape. For the I\!P-p topology, the EPOS-LHC, QGSJET~II and HIJING predictions are significantly lower than the data, what can be explained by a contribution of ultra-peripheral photoproduction events. The obtained data may be of significant input for understanding the high energy limit of QCD and modeling cosmic ray air showers.

• Proton reconstruction with the Precision Proton Spectrometer (PPS) in Run 2 and the PPS at HL-LHC

  Fabrizio Ferro

  SciPost Phys. Proc. 8, 062 (2022) · published 12 July 2022 | Toggle abstract · pdf

  The Precision Proton Spectrometer (PPS) started operating in 2016 and has collected more than 110 fb$^{-1}$ of data over the course of the LHC Run 2, now fully available for physics analysis. This contribution covers the key features of the PPS alignment and optics calibration, which have been developed from scratch. The reconstructed proton distributions, the performance of the PPS simulation and finally the validation of the full reconstruction chain with physics data (dilepton events) are also illustrated.

• Prospects of a future multi-TeV muon collider

  M. Casarsa

  SciPost Phys. Proc. 8, 061 (2022) · published 12 July 2022 | Toggle abstract · pdf

  A multi-TeV muon collider is a discovery machine and an invaluable tool for many new standard model precision measurements such as the shape of the Higgs boson potential. The update of the European Strategy for Particle Physics recognized the unique opportunity of a muon collider to reach the energy frontier, despite the challenges to produce intense collimated muon beams. The options of a collider at 3 TeV and a collider at 10 TeV or above are the main focus of the forming International Muon Collider Collaboration as well as of the discussion panels at the ongoing US Snowmass process.

• Non-zero transverse single spin asymmetry of very forward $\pi^0$ in polarized $p + p$ collisions at $\sqrt{s} = 510$ GeV

  Minho H. Kim

  SciPost Phys. Proc. 8, 060 (2022) · published 12 July 2022 | Toggle abstract · pdf

  The RHICf experiment measured transverse single spin asymmetry of very forward ($\eta > 6$) $\pi^0$ from polarized $p + p$ collisions at $\sqrt{s} = 510$ GeV. In order to measure it precisely, we installed a new electromagnetic calorimeter at zero-degree area of the STAR experiment at the Relativistic Heavy Ion Collider (RHIC) and measured the $\pi^0$s over the kinematic range of $x_F > 0.25$ and $0 < p_T < 1$ GeV/$c$ in June, 2017. A clear non-zero asymmetry was observed even in low $p_T < 1$ GeV$c$ showing a similar $x_F$ dependence with the forward ($2 < \eta < 4$) $\pi^0$ ones. A possible diffractive contribution may need to be taken into account to explain the very forward $\pi^0$ asymmetry. RHICf-STAR combined analysis and follow-up experiment will give a clue to understand it qualitatively.

• Measurement of splittings along a jet shower in $\sqrt{s} = 200$ GeV pp collisions at STAR

  Raghav Kunnawalkam Elayavalli

  SciPost Phys. Proc. 8, 059 (2022) · published 12 July 2022 | Toggle abstract · pdf

  Jets are algorithmic proxies of hard scattered partons, i.e. quarks and gluons, in high energy particle collisions. The STAR collaboration presents the first measurements of substructure observables at the first, second and third splits in the jet clustering tree via the iterative SoftDrop procedure. For each of these splits, we measure the fully corrected groomed shared momentum fraction (\zg) and groomed jet radius (\rg). We discuss the evolution of jet substructure in both the angular and momentum scales which allows for a self-similarity test of the DGLAP splitting function. We compare the fully corrected data to Monte Carlo models, providing stringent constraints on model parameters related to the parton shower and non-perturbative effects such as hadronization.

• Investigation of the background in coherent $J/\psi$ production at the EIC

  Wan Chang

  SciPost Phys. Proc. 8, 053 (2022) · published 12 July 2022 | Toggle abstract · pdf

  Understanding fundamental properties of nucleons and nuclei are among the most important scientific goals of the next-generation machine, the Electron-Ion Collider (EIC). With the unprecedented versatility provided by the EIC, it will provide answers to many standing puzzles and open questions in modern nuclear physics. One of the golden measurements at the EIC is coherent vector meson production in electron-nucleus (eA) scattering in order to obtain the spatial gluon density distribution in heavy nuclei. This requires the experiment to overcome an overwhelmingly large background arising from the incoherent diffractive production, where the nucleus mostly breaks up into fragments of particles in the far-forward direction close to the hadron beam rapidity. In this talk, we systematically study the rejection of incoherent $J/\psi$ production by vetoing products from the nuclear breakup - protons, neutrons, and photons, which is modeled with the BeAGLE event generator and the most up-to-date EIC Far-forward Interaction Region design.

• The LHCspin project

  M. Santimaria, V. Carassiti, G. Ciullo, P. Di Nezza, P. Lenisa, S. Mariani, L. L. Pappalardo, E. Steffens

  SciPost Phys. Proc. 8, 050 (2022) · published 12 July 2022 | Toggle abstract · pdf

  Broad and unexplored kinematic regions can be accessed at the LHC with fixed-target $pp$, $pA$ and $PbA$ collisions at $\sqrt{s_{\rm{NN}}}=72-115~\rm{GeV}$. The LHCb detector is a fully-instrumented forward spectrometer able to run in fixed-target mode, and currently hosts a target gas cell to take data in the upcoming Run 3. The LHCspin project aims at extending this physics program to Run 4 and to bring polarised physics at the LHC. An overview of the physics potential and a description of the LHCspin experimental setup are presented.

  2 citations

• Di-$\pi^0$ correlations in p+p, p+Al and p+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV at STAR

  Xiaoxuan Chu

  SciPost Phys. Proc. 8, 043 (2022) · published 12 July 2022 | Toggle abstract · pdf

  The STAR Collaboration reports measurements of back-to-back azimuthal correlations of di-$\pi^0$ produced at forward pseudorapidity ($2.6<\eta<4.0$) in $p+$$p$, $p+$$\mathrm{Al}$ and $p+$$\mathrm{Au}$ collisions at a center-of-mass energy per nucleon-nucleon pair of 200 GeV. A clear suppression of the correlated away-side yields is observed in $p+$$\mathrm{Au}$ and for the first time in $p+$$\mathrm{Al}$ collisions, compared with the $p$$+$$p$ data. The enhanced suppression found in $p+$$\mathrm{Au}$ with respect to $p+$$\mathrm{Al}$ collisions exhibits the saturation scale ($Q_s^2$) dependence on the mass number~~$A$. The observed suppression of back-to-back pairs as a function of event activity and transverse momentum points to non-linear gluon dynamics arising at high parton densities.

  1 citation

• Study of Short-Range nuclear Correlations in light nuclei using the BeAGLE event generator

  Zhoudunming Tu

  SciPost Phys. Proc. 8, 042 (2022) · published 12 July 2022 | Toggle abstract · pdf

  Nuclear dynamics at short distances among nucleons is one of the most outstanding phenomena in nuclear physics. Understanding the role of QCD in generating nuclear forces is important for uncovering the underlying physics of Short-Range Correlations (SRCs). In recent years, SRCs has been observed from light to heavy nuclei using fixed target experiments at Jefferson lab via high energy electron-nucleus scattering. In this talk, I will talk about the opportunity of studying SRCs using light nuclei with collider experiments, e.g., the Electron Ion Collider (EIC). The experimental technique of studying the light nuclei can be based on exclusive processes with tagging final-state particles, in order to fully control the initial state of the target wavefunction. In particular, incoherent diffractive production of $J/\psi$ particle off deuteron will be presented. In addition, the spectral function in light nuclei has been recently modeled in the BeAGLE event generator, where the decay kinematics of the light nuclei and their influence on the very forward detector design at the EIC will be discussed.

• Measurements of W and Z boson production in ATLAS

  Zhibo Wu

  SciPost Phys. Proc. 8, 031 (2022) · published 11 July 2022 | Toggle abstract · pdf

  Precision measurements of the production cross-sections of W and Z boson at LHC provide important tests of perturbative QCD and information about the parton distribution functions for quarks within the proton. We present measurements of cross sections for inclusive $W^+$, $W^{-}$ and Z boson production using data collected by the ATLAS experiment at a center-of-mass energy of $\sqrt{s}$=2.76 TeV. Measurement of the transverse momentum distribution of Z boson at $\sqrt{s}$=13 TeV is also presented. The measurements are corrected for detector effects and compared with state-of-the-art theoretical calculations.