Fri·Mar 31, 2023Friday·March 31, 2023

1. 01*

   Probing small Bjorken-$x$ nuclear gluonic structure via coherent J/$\psi$ photoproduction in ultraperipheral PbPb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV

   CMS Collaboration

   Quasireal photons exchanged in relativistic heavy ion interactions are powerful probes of the gluonic structure of nuclei. The coherent J/$\psi$ photoproduction cross section in ultraperipheral lead-lead collisions is measured as a function of photon-nucleus center-of-mass energies per nucleon (W${}_{\gamma \text{N}}^{\text{Pb}}$), over a wide range of 40 $<$ W${}_{\gamma \text{N}}^{\text{Pb}}$ $<$ 400 GeV. Results are obtained using data at the nucleon-nucleon center-of-mass energy of 5.02 TeV collected by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of 1.52 nb${}^{-1}$. The cross section is observed to rise rapidly at low W${}_{\gamma \text{N}}^{\text{Pb}}$, and plateau above W${}_{\gamma \text{N}}^{\text{Pb}}$ $\approx$ 40 GeV, up to 400 GeV, a new regime of small Bjorken-$x$ ($\approx$ 6 $\times$ 10${}^{-5}$) gluons being probed in a heavy nucleus. The observed energy dependence is not predicted by current quantum chromodynamic models.

   nucl-exhep-exPRL(2023)·117 citations
2. 02*

   Hot QCD White Paper

   M. Arslandok🇺🇸 · S. A. Bass🇺🇸 · A. A. Baty🇺🇸 · I. Bautista🇲🇽 · C. Beattie🇺🇸 · F. Becattini🇮🇹 · R. Bellwied🇺🇸 · Y. Berdnikov🇷🇺 · A. Berdnikov🇷🇺 · J. Bielcik🇨🇿 · J. T. Blair🇺🇸 · F. Bock🇺🇸 and 162 other authors

   Hot QCD physics studies the nuclear strong force under extreme temperature and densities. Experimentally these conditions are achieved via high-energy collisions of heavy ions at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). In the past decade, a unique and substantial suite of data was collected at RHIC and the LHC, probing hydrodynamics at the nucleon scale, the temperature dependence of the transport properties of quark-gluon plasma, the phase diagram of nuclear matter, the interaction of quarks and gluons at different scales and much more. This document, as part of the 2023 nuclear science long range planning process, was written to review the progress in hot QCD since the 2015 Long Range Plan for Nuclear Science, as well as highlight the realization of previous recommendations, and present opportunities for the next decade, building on the accomplishments and investments made in theoretical developments and the construction of new detectors. Furthermore, this document provides additional context to support the recommendations voted on at the Joint Hot and Cold QCD Town Hall Meeting, which are reported in a separate document.

   nucl-exhep-exhep-phnucl-th125 citations
3. 03*

   Measurement of the Sensitivity of Two-Particle Correlations in $pp$ Collisions to the Presence of Hard Scatterings

   ATLAS Collaboration

   A key open question in the study of multi-particle production in high-energy $pp$ collisions is the relationship between the "ridge'' - observed azimuthal correlations between particles in the underlying event that extend over all rapidities - and hard or semi-hard scattering processes. In particular, it is not known whether jets or their soft fragments are correlated with particles in the underlying event. To address this question, two-particle correlations are measured in $pp$ collisions at $\sqrt{s}=13$ TeV using data collected by the ATLAS experiment at the LHC, with an integrated luminosity of $15.8$ ${\mathrm{pb}}^{-1}$, in two different configurations. In the first case, charged particles associated with jets are excluded from the correlation analysis, while in the second case, correlations are measured between particles within jets and charged particles from the underlying event. Second-order flow coefficients, $v_2$, are presented as a function of event multiplicity and transverse momentum. These measurements show that excluding particles associated with jets does not affect the measured correlations. Moreover, particles associated with jets do not exhibit any significant azimuthal correlations with the underlying event, ruling out hard processes contributing to the ridge.

   nucl-exhep-exPRL(2023)·15 citations
4. 04*

   Examination of cluster production in excited light systems at Fermi energies from new experimental data and comparison with transport model calculations

   C. Frosin🇮🇹 · S. Piantelli🇮🇹 · G. Casini🇮🇹 · A. Ono🇯🇵 · A. Camaiani🇧🇪 · L. Baldesi🇮🇹 · S. Barlini🇮🇹 · B. Borderie🇫🇷 · R. Bougault🇫🇷 · C. Ciampi🇮🇹 · M. Cicerchia🇮🇹 · A. Chbihi🇫🇷 and 35 other authors

   Four different reactions, ${}^{32}$S+${}^{12}$C and ${}^{20}$Ne+${}^{12}$C at 25 and 50 MeV/nucleon, have been measured with the FAZIA detector capable of full isotopic identification of most forward emitted reaction products. Fragment multiplicities, angular distributions and energy spectra have been measured and compared with Monte Carlo simulations, i.e. the antisymmetrized molecular dynamics (AMD) and the heavy-ion phase space exploration (HIPSE) models. These models are combined with two different afterburner codes (HF$l$ and SIMON) to describe the decay of the excited primary fragments. In the case of AMD, the effect of including the clustering and inter-clustering processes to form bound particles and fragments is discussed. A clear confirmation of the role of cluster aggregation in the reaction dynamics and particle production for these light systems, for which the importance of the clustering process increases with bombarding energy, is obtained.

   nucl-exnucl-thPRC(2023)·24 citations
5. 05*

   Theoretical and Experimental Constraints for the Equation of State of Dense and Hot Matter

   Rajesh Kumar🇺🇸 · Veronica Dexheimer🇺🇸 · Johannes Jahan🇺🇸 · Jorge Noronha🇺🇸 · Jacquelyn Noronha-Hostler🇺🇸 · Claudia Ratti🇺🇸 · Nico Yunes🇺🇸 · Angel Rodrigo Nava Acuna🇺🇸 · Mark Alford🇺🇸 · Mahmudul Hasan Anik🇺🇸 · Debarati Chatterjee🇮🇳 · Katerina Chatziioannou🇺🇸 and 48 other authors

   This review aims at providing an extensive discussion of modern constraints relevant for dense and hot strongly interacting matter. It includes theoretical first-principle results from lattice and perturbative QCD, as well as chiral effective field theory results. From the experimental side, it includes heavy-ion collision and low-energy nuclear physics results, as well as observations from neutron stars and their mergers. The validity of different constraints, concerning specific conditions and ranges of applicability, is also provided.

   ↳ nucl-thastro-ph.HEgr-qchep-ph+1Living Rev.Rel.(2024)·171 citations
6. 06*

   Observation of the ${\rm Y}$(3S) meson and suppression of ${\rm Y}$ states in PbPb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV

   CMS Collaboration

   The production of ${\rm Y}$(2S) and ${\rm Y}$(3S) mesons in lead-lead (PbPb) and proton-proton (pp) collisions is studied in their dimuon decay channel using the CMS detector at the LHC. The ${\rm Y}$(3S) meson is observed for the first time in PbPb collisions, with a significance above five standard deviations. The ratios of yields measured in PbPb and pp collisions are reported for both the ${\rm Y}$(2S) and ${\rm Y}$(3S) mesons, as functions of transverse momentum and PbPb collision centrality. These ratios, when appropriately scaled, are significantly less than unity, indicating a suppression of ${\rm Y}$ yields in PbPb collisions. This suppression increases from peripheral to central PbPb collisions. Furthermore, the suppression is stronger for ${\rm Y}$(3S) mesons compared to ${\rm Y}$(2S) mesons, extending the pattern of sequential suppression of quarkonium states in nuclear collisions previously seen for the $\psi$/J, $\psi$(2S), ${\rm Y}$(1S), and ${\rm Y}$(2S) mesons.

   ↳ hep-exnucl-exPRL(2024)·62 citations
7. 07*

   A Deep Learning Approach to Extracting Nuclear Matter Properties from Neutron Star Observations

   Plamen G. Krastev (Harvard University)🇺🇸

   Understanding the equation of state of dense QCD matter remains a major challenge in both nuclear physics and astrophysics. Neutron star observations from electromagnetic and gravitational wave spectra provide critical insights into the behavior of dense neutron-rich matter. The next generation of telescopes and gravitational wave observatories will offer even more detailed observations of neutron stars. Utilizing deep learning techniques to map neutron star mass and radius observations to the equation of state allows for its accurate and reliable determination. This work demonstrates the feasibility of using deep learning to extract the equation of state directly from neutron star observational data, and to also obtain related nuclear matter properties such as the slope, curvature, and skewness of the nuclear symmetry energy at saturation density. Most importantly, we show that this deep learning approach is able to reconstruct \textit{realistic} equations of state, and deduce \textit{realistic} nuclear matter properties. This highlights the potential of artificial neural networks in providing a reliable and efficient means to extract crucial information about the equation of state and related properties of dense neutron-rich matter in the era of multi-messenger astrophysics.

   ↳ nucl-thastro-ph.HEnucl-exSymmetry(2023)·28 citations
8. 08*

   Cumulants from fluctuating width of rapidity distribution

   Michał Barej🇵🇱 · Adam Bzdak🇵🇱

   In relativistic heavy-ion collisions, the longitudinal fluctuations of the fireball density caused, e.g., by baryon stopping fluctuations result in event-by-event modifications of the shape of the proton rapidity density distribution. The multiparticle rapidity correlation functions due to the varying distribution width of the proton rapidity density in central Au+Au collisions at low energies are derived. The cumulant ratios are calculated and discussed in the context of the recent STAR Collaboration results. We find that the cumulant ratios for small width fluctuations seem to be universal.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2023)·1 citation
9. 09*

   Small-$x$ Quark and Gluon Helicity Contributions to the Proton Spin Puzzle

   Yossathorn Tawabutr🇫🇮

   A small-$x$ helicity evolution has been derived in 2016-18 and received an important modification in 2022. This article discusses its general framework and summarizes the recent theoretical developments, including the asymptotic behaviors of helicity PDFs and $g_1$ structure function at small $x$. The latest fits to various polarized scattering data are also discussed. The results from this research program will provide important theoretical inputs for the future polarized small-$x$ measurements at the electron-ion collider (EIC).

   ↳ hep-phhep-exnucl-exnucl-thActa Phys.Polon.Supp.(2023)·3 citations

* 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.