Wed·Apr 26, 2023Wednesday·April 26, 2023

1. 01*

   Exclusive and dissociative J/$\psi$ photoproduction, and exclusive dimuon production, in p$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}=8.16$ TeV

   ALICE Collaboration

   The ALICE Collaboration reports three measurements in ultra-peripheral proton$-$lead collisions at forward rapidity. The exclusive two-photon process \ggmm and the exclusive photoproduction of J/$\psi$ are studied. J/$\psi$ photoproduction with proton dissociation is measured for the first time at a hadron collider. The cross section for the two-photon process of dimuons in the invariant mass range from 1 to 2.5 GeV/$c^2$ agrees with leading order quantum electrodynamics calculations. The exclusive and dissociative cross sections for J/$\psi$ photoproductions are measured for photon$-$proton centre-of-mass energies from 27 to 57 GeV. They are in good agreement with HERA results.

   nucl-exhep-exPRD(2023)·38 citations
2. 02*

   Polarised parton distribution functions and proton spin

   Peng Cheng🇨🇳 · Yang Yu🇨🇳 · Hui-Yu Xing🇨🇳 · Chen Chen🇨🇳 · Zhu-Fang Cui🇨🇳 · Craig D. Roberts🇨🇳

   Supposing there exists an effective charge which defines an evolution scheme for both unpolarised and polarised parton distribution functions (DFs) that is all-orders exact and using Ansätze for hadron-scale proton polarised valence quark DFs, constrained by flavour-separated axial charges and insights from perturbative quantum chromodynamics, predictions are delivered for all proton polarised DFs at the scale ${\zeta }_{\mathrm{C}}^2=3$GeV${}^2$. The pointwise behaviour of the predicted DFs and, consequently, their moments, compare favourably with results inferred from data. Notably, flavour-separated singlet polarised DFs are small. On the other hand, the polarised gluon DF, $\Delta G(x;{\zeta }_{\mathrm{C}})$, is large and positive. Using our result, we predict ${\int }_{0.05}^{1}dx\Delta G(x;{\zeta }_{\mathrm{C}})=0.214(4)$ and that experimental measurements of the proton flavour-singlet axial charge should return $a_0^{\mathrm{E}}({\zeta }_{\mathrm{C}})=0.35(2)$.

   ↳ hep-phhep-exhep-latnucl-ex+1PLB(2023)·29 citations
3. 03*

   Ultra-peripheral nuclear collisions

   C. A. Bertulani🇺🇸

   This article presents a very brief review of the physics of Ultra-Peripheral Collisions (UPC) at the Large Hadron Collider (LHC) and other nuclear facilities. I discuss several processes of interest such as electron-position pair production, the anti-hydrogen atom, giant resonances, exotic meson production and parton distribution functions.

   ↳ hep-phnucl-exnucl-thJ.Phys.Conf.Ser.(2023)·5 citations
4. 04*

   An Augmented QCD Phase Portrait: Mapping Quark-Hadron Deconfinement for Hot, Dense, Rotating Matter under Magnetic Field

   Gaurav Mukherjee🇮🇳 · D. Dutta🇮🇳 · D. K. Mishra🇮🇳

   The quark-hadron transition that happens in ultra-relativistic heavy-ion collisions is expected to be influenced by the effects of rotation and magnetic field, both present due to the geometry of a generic non-head-on impact. We augment the conventional $T$--${\mu }_B$ planar phase diagram for QCD matter by extending it to a multi-dimensional domain spanned by temperature $T$, baryon chemical potential ${\mu }_B$, external magnetic field $B$ and angular velocity $\omega$. Using two independent approaches, one from a rapid rise in entropy density and another dealing with a dip in the squared speed of sound, we identify deconfinement in the framework of a modified statistical hadronization model. We find that the deconfinement temperature $T_C({\mu }_B,\omega ,eB)$ decreases nearly monotonically with increasing ${\mu }_B,\omega$ and $eB$ with the most prominent drop (by nearly $40$ to $50$ MeV) in $T_C$ occurring when all the three quasi-control (via collision energy and centrality) parameters are simultaneously tuned to finite values that are typically achievable in present and upcoming heavy-ion colliders.

   ↳ hep-phnucl-exnucl-thPLB(2023)·14 citations
5. 05*

   Random model of flow decorrelation

   Piotr Bozek🇵🇱 · Hadi Mehrabpour🇩🇪

   The collective flow generated in relativistic heavy-ion collisions fluctuates from event to event. The fluctuations lead to a decorrelation of flow vectors measured in separate bins in phase space. These effects have been measured in experiments and observed in numerical simulations in hydrodynamic models. We present a simple random model of flow decorrelation in pseudorapidity. Analytical expressions for the flow factorization breaking coefficients for flow vectors, flow vector magnitudes, and flow angles are derived. The model explains the relations between different factorization breaking coefficients found in experimental data and model simulations. In particular, it is found that the flow angle decorrelation constitutes about one half of the total flow vector decorrelation.

   ↳ nucl-thhep-phnucl-exPRC(2023)·3 citations
6. 06*

   The TULIP project : first on-line result and near future

   V. Bosquet🇫🇷 · P. Jardin🇫🇷 · M. MacCormick🇫🇷 · C. Michel🇫🇷

   The TULIP project aims to produce radioactive ion beams of short-lived neutron-deficient isotopes by using fusion-evaporation reactions in an optimized Target Ion Source System (TISS). The first step consisted of the design of a TISS to produce rubidium isotopes. It was tested with a primary beam of ${}^{22}$Ne@4.5 MeV/A irradiating a natural Ni target at the SPIRAL1/GANIL facility in March 2022. Rates of ${}^{76,78}$Rb were measured as well as an exceptionally short atom-to-ion transformation time for an ISOL system, of the order of 200 $\text{micro}$s. The second step of the project aims at producing neutron-deficient short-lived metallic isotopes in the region of ${}^{100}$Sn. A "cold" prototype has been realized to study the electron impact ionization in the TISS cavity and a "hot" version is under construction to prepare an on-line experiment expected in the near future.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.B(2023)·1 citation

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.