Wed·Sep 17, 2025Wednesday·September 17, 2025

1. 01*

   Unveiling the shape of the ${}^{20}$Ne nucleus by measuring the flow coefficients with cumulants in PbNe and PbAr collisions at $\sqrt{s_{NN}}=70.9$ GeV

   LHCb collaboration

   The anisotropic flow coefficients $v_n$ quantify the collective medium response to the initial spatial anisotropy of the overlapping region in ion collisions and serve as sensitive probes of both the medium properties and shape of nuclear initial states. In this analysis, the $v_2$ and $v_3$ parameters of prompt charged particles are measured using the multiparticle cumulant method in fixed-target PbNe and PbAr collisions at $\sqrt{s_{NN}}=70.9$ GeV, collected by LHCb using the SMOG2 gas-target system during the 2024 LHC lead-beam run. The cumulant method is first validated using 2018 PbPb collision data, successfully reproducing previous measurements obtained via the two-particle correlation method. Results for the fixed-target collisions are then presented, showing a significantly larger value of the elliptic flow coefficient $v_2$ in central PbNe with respect to PbAr collisions. This is qualitatively consistent with 3+1D hydrodynamic predictions including ab-initio descriptions of the nuclear structure. The results provide the first experimental confirmation of the distinctive bowling-pin shape of the ground-state ${}^{20}$Ne nucleus, validating at the same time the hydrodynamic description of the hot medium formed in high-energy collisions involving light ions.

   nucl-exhep-ex2 citations
2. 02*

   Observation of charmonium sequential suppression in heavy-ion collisions at the Relativistic Heavy Ion Collider

   STAR Collaboration: B. E. Aboona · J. Adam · L. Adamczyk · I. Aggarwal · M. M. Aggarwal · Z. Ahammed · A. K. Alshammri · E. C. Aschenauer · S. Aslam · J. Atchison · V. Bairathi · X. Bao and 384 other authors

   We report measurements of charmonium sequential suppression in Ru+Ru and Zr+Zr collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV with the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). The inclusive yield ratio of $\psi$(2S) to J/$\psi$ as a function of transverse momentum is reported, along with the centrality dependence of the double ratio, defined as the $\psi$(2S) to J/$\psi$ ratio in heavy-ion collisions relative to that in $p$+$p$ collisions. In the 0-80% centrality class, the double ratio is found to be 0.41 $\pm$ 0.10 (stat) $\pm$ 0.03 (syst) $\pm$ 0.02 (ref), lower than unity with a significance of 5.6 standard deviations. This provides experimental evidence that $\psi$(2S) is significantly more suppressed than J/$\psi$ in heavy-ion collisions at RHIC. This sequential suppression pattern seems to increase from peripheral to central collisions, but with no significant dependence on the transverse momentum.

   nucl-exhep-exPRL(2026)·10 citations
3. 03*

   Nonresonant capture cross section measurement of the 29Si(p,gamma)30P reaction

   Zs Mátyus · L Csedreki · Zs Fülöp · Z Halász🇭🇺 · G G Kiss🇯🇵 · T Szücs🇭🇺 · Á Tóth · Gy Gyürky🇭🇺

   The isotopic ratios measured in meteoritic presolar grains are a crucial tool for tracing the nucleosynthetic origin of isotopes. In the case of silicon isotopes, two important indicators to establish the origin of presolar grains are the ratios 29Si/28Si and 30Si/28Si. To constrain theoretical predictions, the rates of key nuclear reactions influencing the abundances of 29Si and 30Si must be well known. One such reaction is 29Si(p,gamma)30P which plays a role in classical nova explosions. The aim of the present work is to determine the nonresonant cross section of the 29Si(p,gamma)30P reaction, which has not been previously measured. The activation method was employed to measure the total cross section at four proton energies between Ep = 1000 and 1430 keV. The measured cross sections were found to be significantly (a factor of 4.3+-0.6) higher than those predicted by theoretical direct capture calculations, thereby impacting the reaction rates at low astrophysical temperatures, below about 30 MK. This higher nonresonant cross section - now based on experimental data - can be used in forthcoming nucleosynthesis calculations of classical novae. As a secondary result, the 16O(p,gamma)17F cross section was also obtained and found to be in good agreement with existing literature data.

   nucl-exastro-ph.SRJ.Phys.G(2025)·0 citations
4. 04*

   Measurement of neutron total cross-section of Mg and MgF${}_2$ at MONNET (JRC-Geel) from transmission with fine multi-scattering corrections

   Marco Antonio Martínez-Cañadas🇪🇸 · Pablo Torres-Sánchez🇪🇸 · Miguel Macías · Javier Praena🇪🇸 · Cristiano L. Fontana · Cédric Bonaldi · Wouter Geerts · Stephan Oberstedt · Ignacio Porras🇪🇸

   Neutron-transmission measurements through samples of magnesium fluoride (MgF${}_2$) and pure magnesium were performed to obtain the (n, tot) cross section for all isotopes involved, ${}^{19}$F and ${}^{24-26}$Mg. Lithium-glass detectors were used in conjunction with the neutron time-of-flight technique. The measurement campaign was performed at the MONNET fast-neutron source of the European Commission Joint Research Centre (JRC-Geel, Belgium). Highly precise corrections for multiple scattering were calculated using a sophisticated iterative method based on Monte Carlo simulations with the MCNP6.3 code, accounting for the effects of the experimental setup. With the SAMMY code, an R-Matrix analysis of the experimental data was performed. The extracted cross-sections, resonance spin and parity as well as the limitations of the method are carefully discussed.

   nucl-ex0 citations
5. 05*

   Search for Quintessence-Like Pseudoscalar Dark Energy Effects on ${}^{56}\text{Fe}$ Nuclear Transition Energies in Supernova 1991T

   Robert D. Orlando🇺🇸 · David S. Koltick🇺🇸 · Dennis E. Krause🇺🇸

   The nature of dark energy remains one of the most important unanswered problems in physics. Here we use gamma-ray spectra from the Type Ia supernova 1991T to constrain the recent evolution of a dynamical pseudoscalar quintessence-like field $Q(t)$. We found that the 1991T gamma rays emitted by the ${}^{56}\text{Fe}$ nuclei observed by COMPTEL aboard the Compton Gamma Ray Observatory were slightly shifted to lower energies with respect to terrestrial values, with the average fractional energy shift of both the first and second excited states found to be $\delta E/E=-0.006\pm 0.008$ including statistical and systematic errors. Assuming that this energy shift is caused by a dynamical QCD axion-like pseudoscalar field $Q(t)$, we find that observed energy deviations are consistent with a fractional rate of change of the pion mass given by $\delta \dot{m_{\pi }}/m_{\pi }=-(6\pm 9)\times 10^{-11}{\text{ yr}}^{-1}$. The observed energy deviation was also used to determine the rate of change of the quintessence-like field (${\dot{Q}}_0$) for tracking models: ${\dot{Q}}_{0,max}=(3\pm 4)\times 10^7\text{ GeV/yr}$. Our findings are consistent with the cosmological constant (${\dot{Q}}_0=0$). Furthermore, we have demonstrated how nuclear spectra produced by astrophysical events can be used to inform the nature and behavior of dark energy.

   ↳ astro-ph.COhep-phnucl-ex0 citations
6. 06*

   Investigation of ground state properties and shape evolution in Hf isotopes using the CDFT approach

   Usuf Rahaman

   The ground-state properties and shape evolution of even-even hafnium isotopes ranging from $N=80$ to the neutron dripline are thoroughly examined using Covariant Density Functional Theory (CDFT) with density-dependent effective interactions, specifically the parameter sets DD-ME1, DD-ME2, DD-PC1, and DD-PCX. Key nuclear properties, including binding energies, two-neutron separation energies ($S_{2n}$), two-neutron shell gaps ($\delta S_{2n}$), neutron pairing energies ($E_{pair,n}$), quadrupole deformation parameters (${\beta }_2$), root-mean-square (RMS) charge and matter radii, and neutron skin thickness ($\Delta r_{np}$), are systematically computed and compared with available experimental results and predictions from various theoretical models. These include the Hartree-Fock-Bogoliubov (HFB) framework employing the Skyrme SLy4 interaction, the Finite Range Droplet Model (FRDM), the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) using the PC-PK1 functional, and the relativistic mean-field (RMF) approach with NL3 parameterization. Shell closures at $N=82$ and $N=126$, subshell effects at $N=108$ and $N=152$, and shape transitions with coexistence in ${}^{192}$Hf and ${}^{222-236}$Hf are observed. Neutron skin thickness increases with neutron excess, and potential energy surfaces show consistent trends, validating CDFT's reliability for nuclear structure predictions.

   ↳ nucl-thnucl-exIJMPE(2025)·2 citations
7. 07*

   Partonic structure of nuclei from UPCs

   V. Guzey (Jyvaskyla U. and Helsinki Inst. of Phys.)🇫🇮

   We present an overview of theoretical and phenomenological studies on the partonic structure of nuclei and small-$x$ QCD dynamics using photon-nucleus $(\gamma A$) scattering in heavy ion ultraperipheral collisions (UPCs). Focusing on nuclear shadowing, we review implications of coherent charmonium and inclusive dijet production in Pb-Pb UPCs at the LHC and discuss the potential of inelastic $\gamma A$ scattering accompanied by forward neutrons in a zero degree calorimeter (ZDC).

   ↳ hep-phhep-exnucl-ex1 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.