Tue·Oct 1, 2024Tuesday·October 1, 2024

1. 01*

   Recent results from NA61/SHINE

   Andrzej Rybicki (for the NA61/SHINE Collaboration)🇵🇱

   The NA61/SHINE experiment at the CERN SPS is a multipurpose fixed-target spectrometer for charged and neutral hadron measurements. Its research program includes studies of strong interactions as well as reference measurements for neutrino and cosmic-ray physics. A significant advantage of NA61/SHINE over collider experiments is its extended coverage of phase space available for hadron production. This includes the nearly entire forward hemisphere for charged hadrons and additionally, a large part of the backward hemisphere for specific neutrals. This paper summarizes a selected set of new results, obtained by NA61/SHINE since the last SQM conference (Busan, 2022). Particular attention is devoted to (1) the first-ever direct measurement of open charm production in nucleus-nucleus collisions at SPS energies (2) the difference observed between charged and neutral meson production in Ar+Sc reactions, up to now not understood by existing models, and (3) the importance of baseline effects in the search for the critical point of strongly interacting matter.

   nucl-exEPJ Web Conf.(2025)·4 citations
2. 02*

   $K^{\ast }/K$ ratio and the time between freeze-outs for intermediate-mass Ar+Sc system at the SPS energy range

   Bartosz Kozłowski (for the NA61/SHINE Collaboration)🇵🇱

   Resonance production is one of the key observables to study the dynamics of high-energy collisions. In dense systems created in heavy nucleus-nucleus collisions, the properties of some of them (widths, masses, branching ratios) were predicted to be modified due to partial restoration of chiral symmetry. The resonance spectra and yields are also important inputs for Blast-Wave and Hadron Resonance Gas models. Finally, the analysis of strange $K^{\ast }(892{)}^0$ resonance allows us to better understand the time evolution of high-energy nucleus-nucleus collision. Namely, the ratio of $K^{\ast }(892{)}^0$ to charged kaons is used to determine the time between chemical and kinetic freeze-outs. In this article, the first results on the analysis of $K^{\ast }(892{)}^0$ production in central Ar+Sc collisions at three SPS energies ($\sqrt{s_{\mathrm{NN}}}$ = 8.8, 11.9, 16.8 GeV) are presented. The $K^{\ast }(892{)}^0/K^{+/-}$ yield ratios are compared with corresponding results in $p$+$p$ collisions, allowing us to estimate the time between chemical and thermal freeze-outs in Ar+Sc collisions. These first results for intermediate-mass nucleus-nucleus systems at the SPS energy range are compared with the results of heavier systems at a similar energy range.

   nucl-exPoS(2025)·5 citations
3. 03*

   Assessing the QGP speed of sound in ultra-central heavy-ion collisions with ALICE

   Omar Vazquez Rueda🇺🇸

   Ultrarelativistic heavy-ion collisions produce a state of hot, dense, strongly interacting QCD matter known as quark-gluon plasma (QGP). On an event-by-event basis, the volume of the QGP in ultra-central collisions is mostly constant, while its total entropy can vary significantly, leading to variations in the temperature of the system. Exploiting this unique feature of ultra-central collisions allows us to interpret the correlation between the mean transverse momentum $(⟨p_{\mathrm{T}}⟩)$ of produced charged hadrons and the number of charged hadrons as a measure of the the speed of sound, $c_s$. The speed of sound, $c_s$, which relates to the speed at which compression waves travel in a medium (in this case the QGP), is determined by fitting the relative increase of $⟨p_{\mathrm{T}}⟩$ with respect to the relative change of the average charged-particle density $(⟨\mathrm{d}{N}_{\mathrm{ch}}/\mathrm{d}\eta ⟩)$ measured at midrapidity. This study reports the $⟨p_{\mathrm{T}}⟩$ of charged particles in ultra-central Pb-Pb collisions at a center-of-mass energy of 5.02 TeV per nucleon pair, using the ALICE detector. Different centrality estimators based on charged-particle multiplicity or the transverse energy of the event are employed to select ultra-central collisions. By ensuring a pseudorapidity gap between the region used to define the centrality and the region used for measurement, the influence of biases and their potential effects on the rise of the mean transverse momentum are tested. The measured $c_s^2$ is found to strongly depend on the type of the centrality estimator, ranging from $0.113\pm 0.003(\mathrm{stat})\pm 0.007(\mathrm{syst})$ to $0.438\pm 0.001(\mathrm{stat})\pm 0.019(\mathrm{syst})$ in natural units.

   nucl-exhep-exPoS(2025)·1 citation
4. 04*

   Probing Nuclear Structure of Heavy Ions at the Large Hadron Collider

   Heikki Mäntysaari🇫🇮 · Björn Schenke🇺🇸 · Chun Shen🇺🇸 · Wenbin Zhao🇺🇸

   We perform high-statistics simulations to study the impacts of nuclear structure on the ratios of anisotropic flow observables in ${}^{208}$Pb+${}^{208}$Pb and ${}^{129}$Xe+${}^{129}$Xe collisions at the Large Hadron Collider. Even with $40\%$ difference in atomic numbers between ${}^{208}$Pb and ${}^{129}$Xe nuclei, the ratios of anisotropic flow in the same centrality class between the two collision systems are strongly affected by the nuclear structure inputs in the initial state. The ratios of $v_2\{4\}/v_2\{2\}$ in these collisions are sensitive to the nuclear skin thickness of the colliding nuclei, providing indirect constraints on the nuclei's neutron skin. Our model predictions serve as a benchmark to compare with experimental measurements.

   ↳ nucl-thhep-phnucl-exPRC(2024)·27 citations
5. 05*

   Athermal phonon collection efficiency in diamond crystals for low mass dark matter detection

   I. Kim🇺🇸 · N. A. Kurinsky🇺🇸 · H. Kagan🇺🇸 · S. T. P. Boyd🇺🇸 · G. B. Kim🇺🇸

   We explored the efficacy of lab-grown diamonds as potential target materials for the direct detection of sub-GeV dark matter~(DM) using metallic magnetic calorimeters~(MMCs). Diamond, with its excellent phononic properties and the low atomic mass of the constituent carbon, can play a crucial role in detecting low-mass dark matter particles. The relatively long electron-hole pair lifetime inside the crystal may provide discrimination power between the DM-induced nuclear recoil events and the background-induced electron recoil events. Utilizing the the fast response times of the MMCs and their unique geometric versatility, we deployed a novel methodology for quantifying phonon dynamics inside diamond crystals. We demonstrated that lab-grown diamond crystals fabricated via the chemical vapor deposition~(CVD) technique can satisfy the stringent quality requirements for sub-GeV dark matter searches. The high-quality polycrystalline CVD diamond showed a superior athermal phonon collection efficiency compared to that of the reference sapphire crystal, and achieved energy resolution 62.7~eV at the 8.05~keV copper fluorescence line. With this energy resolution, we explored the low-energy range below 100~eV and confirmed the existence of so-called low-energy excess~(LEE) reported by multiple cryogenic experiments.

   ↳ physics.ins-dethep-exnucl-exPRD(2025)·5 citations
6. 06*

   Exploring the Diversity of Nuclear Density through Information Entropy

   Wei-Hu Ma🇨🇳 · Yu-Gang Ma🇨🇳

   This study explores the role of information entropy in understanding nuclear density distributions, including both stable configurations and non-traditional structures such as neutron halos and $\alpha$-clustering. By quantifying the uncertainty and disorder inherent in nucleon distributions in nuclear many-body systems, information entropy provides a macroscopic measure of the physical properties of the system. A more dispersed and disordered density distribution results in a higher value of information entropy. This intrinsic relationship between information entropy and system complexity allows us to quantify uncertainty and disorder in nuclear structures by analyzing various geometric parameters such as nuclear radius, diffuseness, neutron skin, and cluster structural features.

   ↳ nucl-thnucl-exEntropy(2024)·3 citations
7. 07*

   On the origin of the peak of the sound velocity for isospin imbalanced strongly interacting matter

   Alejandro Ayala🇲🇽 · Bruno S. Lopes🇧🇷 · Ricardo L. S. Farias🇧🇷 · Luis C. Parra🇲🇽

   We study the properties of a system composed of strongly interacting matter with an isospin imbalance, using as an effective description of QCD the two-flavor Linear Sigma Model with quarks. From the one-loop effective potential, including the two light quarks, pions and sigma contributions, and enforcing the restrictions imposed by chiral symmetry, we show that the development of an isospin condensate comes together with the emergence of a Goldstone mode that provides a constraint for the chiral and isospin condensates as a result of a non-trivial mixing between the charged pions and the sigma. We compute the thermodynamical quantities of interest and in particular the sound velocity squared, showing that it presents a maximum for an isospin chemical potential similar to the one reported by lattice QCD results and also with a similar height. Therefore, we attribute the origin of the peak of the sound velocity to the proper treatment of the Goldstone mode and to the non-trivial mixing of the charged pions and sigma in the isospin condensed phase.

   ↳ hep-phhep-latnucl-exnucl-thPLB(2025)·17 citations
8. 08*

   Hypercontractivity and factorial moment scaling in the symmetry broken phase

   Athanasios Brofas🇬🇷 · Manolis Zampetakis🇺🇸 · Fotios Diakonos🇬🇷

   The search for remnants of the QCD chiral critical point is a central objective of current and future high-energy ion collision experiments. Previous studies suggest that a scaling law relating higher-order factorial moments of hadron multiplicity fluctuations to the second factorial moment could serve as a tool for detecting the QCD critical point. However, we demonstrate that this scaling law is not unique to critical phenomena. Instead, it emerges as a general property of distributions by extending the concept of hypercontractivity, originally applied to ordinary moments, to factorial moments. We present examples of distribution classes that exhibit the same higher-order factorial moment scaling as multiplicity fluctuations in the symmetry-broken phase. This insight allows us to explain the recent intermittency analysis results from the STAR experiment at RHIC (arXiv:2301.11062), where no indication of criticality was observed.

   ↳ hep-phhep-exhep-thnucl-ex+1PLB(2025)·3 citations
9. 09*

   SMASH as an event generator for heavy-ion collisions

   A. Sciarra🇩🇪 · H. Elfner🇩🇪

   In this article we present an overview of the SMASH hadronic transport approach that is applied for non-equilibrium dynamics of hadrons in \heavyion\ collisions. We will give an overview about the ingredients of the approach and the applications for the dynamical description of \heavyion\ collisions and for calculations of fundamental properties of the hadron gas. The main emphasis of the article will be the infrastructure for sustainable software development that we have developed over the last 10 years including extensive unit tests and continuous integration. We will also provide one section about the performance of the code and how it can be analyzed and improved in the future.

   ↳ nucl-thnucl-exFront.in Phys.(2024)·7 citations
10. 10*

    Complete 1-loop study of exclusive $J/\psi$ and ${\rm Y}$ photoproduction with full GPD evolution

    Chris Flett🇫🇷 · Jean-Philippe Lansberg🇫🇷 · Saad Nabeebaccus🇫🇷 · Maxim Nefedov🇫🇷 · Pawel Sznajder🇵🇱 · Jakub Wagner🇵🇱

    We discuss the exclusive photoproduction of a heavy vector quarkonium, namely $J/\psi$ and ${\rm Y}$ at 1-loop in ${\alpha }_s$. In collinear factorisation (CF), the amplitude for such a process is obtained by the convolution of a hard partonic sub-amplitude, with a universal generalised parton distribution (GPD). For the first time, we perform a complete calculation at 1-loop including full leading-log (LL) GPD evolution. We first demonstrate the huge instability of the cross section at high energies when the factorisation scale ${\mu }_F$ is varied. This instability has been reported previously in the literature, and occurs due to the large logarithms generated by the huge difference between the hard scale of the process, which is the mass of the heavy quarkonium here, and the centre-of-mass energy of the process. This problem was also reported in inclusive heavy vector quarkonium photoproduction. We show that this issue can be resolved by resumming these large logarithms using high-energy factorisation (HEF), by performing a matching with the result in CF using the doubly logarithmic approximation (DLA) in order to be consistent with the fixed order evolution of GPDs. Finally, we show that the cross sections obtained from such a matching, besides being free from the previously mentioned factorisation scale variation instabilities, are consistent with the H1 data for $J/\psi$ production and with the ZEUS data for ${\rm Y}$ production.

    ↳ hep-phhep-exnucl-exnucl-thPoS(2025)·0 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.