Mon·Sep 30, 2024Monday·September 30, 2024

1. 01*

   Remeasurement of the ${}^{239}$Pu(n,f)/${}^{235}$U(n,f) Cross-Section Ratio with the NIFFTE fission Time Projection Chamber Using Vapor-deposited Targets

   D.H. Dongwi🇺🇸 · L. Snyder · V. Aguilar · N. Androski · M. Anastasiou🇺🇸 · N.S. Bowden🇺🇸 · A. Chemey🇺🇸 · T. Classen🇺🇸 · J.E. Fuzaro Alencar · U. Greife🇺🇸 · M. Haseman · L.D. Isenhower and 8 other authors

   The NIFFTE fission Time Projection Chamber (fissionTPC) has been used to measure the ${}^{239}$Pu(n,f)/${}^{235}$U(n,f) cross-section ratio for neutron-induced fission in the range of 0.1 - 100 MeV, with high precision. A white neutron source was provided by the Los Alamos Neutron Science Center, where the experiment was conducted as a remeasurement to evaluate a roughly 2% discrepancy of the previous fissionTPC results with ENDF/B-VIII.0. A detailed accounting of measurement uncertainties was performed, based on the fissionTPC's novel ability to provide three-dimensional reconstruction of fission-fragment ionization profiles. Current results obtained using a vapor-deposited, highly uniform ${}^{239}$Pu target, in comparison to the measurement published in 2021, where a ${}^{239}$Pu electroplated target was used, are presented and discussed. The remeasurement presented here is in agreement with the previous fissionTPC result within measurement uncertainties.

   nucl-ex0 citations
2. 02*

   The glue that binds us all -- Latin America and the Electron-Ion Collider

   A. C. Aguilar🇧🇷 · A. Bashir🇲🇽 · J. J. Cobos-Martínez🇲🇽 · A. Courtoy🇲🇽 · B. El-Bennich🇧🇷 · D. de Florian🇦🇷 · T. Frederico🇧🇷 · V. P. Gonçalves🇧🇷 · M. Hentschinski🇲🇽 · R. J. Hernández-Pinto🇲🇽 · G. Krein🇧🇷 · M. V. T. Machado🇧🇷 and 14 other authors

   The Electron-Ion Collider, a next generation electron-hadron and electron-nuclei scattering facility, will be built at Brookhaven National Laboratory. The wealth of new data will shape research in hadron physics, from nonperturbative QCD techniques to perturbative QCD improvements and global QCD analyses, for the decades to come. With the present proposal, Latin America based physicists, whose expertise lies on the theory and phenomenology side, make the case for the past and future efforts of a growing community, working hand-in-hand towards developing theoretical tools and predictions to analyze, interpret and optimize the results that will be obtained at the EIC, unveiling the role of the glue that binds us all. This effort is along the lines of various initiatives taken in the U.S., and supported by colleagues worldwide, such as the ones by the EIC User Group which were highlighted during the Snowmass Process and the Particle Physics Project Prioritization Panel (P5).

   nucl-exhep-exhep-lathep-ph+1Braz.J.Phys.(2025)·4 citations
3. 03*

   First Measurement of Near- and Sub-Threshold $J/\psi$ Photoproduction off Nuclei

   J.R. Pybus🇺🇸 · L. Ehinger🇺🇸 · T. Kolar🇮🇱 · B. Devkota🇺🇸 · P. Sharp🇺🇸 · B. Yu🇺🇸 · M.M. Dalton🇺🇸 · D. Dutta🇺🇸 · H. Gao🇺🇸 · O. Hen🇺🇸 · E. Piasetzky🇮🇱 · S.N. Santiesteban🇺🇸 and 56 other authors

   We report on the first measurement of $J/\psi$ photoproduction from nuclei in the photon energy range of $7$ to $10.8$ GeV, extending above and below the photoproduction threshold in the free proton of $\sim 8.2$ GeV. The experiment used a tagged photon beam incident on deuterium, helium, and carbon, and the GlueX detector at Jefferson Lab to measure the semi-inclusive $A(\gamma ,e^{+}{e}^{-}p)$ reaction with a dilepton invariant mass $M(e^{+}{e}^{-})\sim m_{J/\psi }=3.1$ GeV. The incoherent $J/\psi$ photoproduction cross sections in the measured nuclei are extracted as a function of the incident photon energy, momentum transfer, and proton reconstructed missing light-cone momentum fraction. Comparisons with theoretical predictions assuming a dipole form factor allow extracting a gluonic radius for bound protons of $\sqrt{⟨r^2⟩}=0.85\pm 0.14$ fm. The data also suggest an excess of the measured cross section for sub-threshold production and for interactions with high missing light-cone momentum fraction protons. The measured enhancement can be explained by modified gluon structure for high-virtuality bound-protons.

   nucl-exPRL(2025)·18 citations
4. 04*

   Charged-particle production in pp collisions at $\sqrt{s}$ = 13.6 TeV and Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.36 TeV with ALICE

   Abhi Modak (for the ALICE Collaboration)🇮🇹

   This article presents the measurement of charged-particle pseudorapidity ($\eta$) density, $\mathrm{d}{N}_{\mathrm{ch}}/\mathrm{d}\eta$, in proton$-$proton (pp) collisions at a centre-of-mass energy $\sqrt{s}$ = 13.6 TeV, and in lead$-$lead (Pb$-$Pb) collisions at a centre-of-mass energy per nucleon pair $\sqrt{s_{\mathrm{NN}}}$ = 5.36 TeV. The analysis is performed using the Run 3 data recorded during 2022 and 2023 by the upgraded ALICE detector. The charged-particle multiplicity is measured at midrapidity ($|\eta |<1$) using the new monolithic active pixel sensors-based Inner Tracking System and the Time Projection Chamber upgraded with Gas Electron Multiplier-based readout system. The measurements in pp collisions are reported for inelastic events with at least one charged particle having $|\eta |<1$ whereas for Pb$-$Pb collisions, the $\mathrm{d}{N}_{\mathrm{ch}}/\mathrm{d}\eta$ is obtained for different centrality classes, ranging from 0$-$5\% (most central) to 70$-$80\% (most peripheral). The energy dependence of average charged-particle pseudorapidity density ($⟨\mathrm{d}{N}_{\mathrm{ch}}/\mathrm{d}\eta ⟩$) measured in $|\eta |<0.5$ is studied and compared to earlier measurements at lower collision energies. In Pb$-$Pb collisions, the evolution of $⟨\mathrm{d}{N}_{\mathrm{ch}}/\mathrm{d}\eta ⟩$ as a function of the average number of participating nucleons, $⟨N_{\mathrm{part}}⟩$, determined with a Glauber model, is also studied and compared with predictions from theoretical models.

   nucl-exhep-exPoS(2025)·1 citation
5. 05*

   Clocking the particle production and tracking of strangeness balance and radial flow effects at top LHC energy with ALICE

   Victor Gonzalez (for the ALICE collaboration)🇺🇸

   Balance functions have been used extensively to elucidate the time evolution of quark production in heavy-ion collisions. Early models predicted two stages of quark production, one for light quarks and one for the heavier strange quark, separated by a period of isentropic expansion. This led to the notion of clocking particle production and tracking radial flow effects, which drive the expansion of the system. In this talk, balance functions of identified particles in different multiplicity classes of pp collisions at $\sqrt{s}=13.6\text{TeV}$ recorded by ALICE during the LHC Run 3 are reported. The results are compared with different models as well as with previously published results on pp and Pb--Pb collisions at different energies. The results enable tracking the balancing of electric charge and strangeness by measuring how the widths and integrals of the charge and strangeness balance functions evolve across different collision energies.

   nucl-exhep-exPoS(2025)·0 citations
6. 06*

   Improved modeling of $\gamma \gamma$ processes in ultraperipheral collisions at hadron colliders

   Nicolas Crépet🇫🇷 · David d'Enterria🇨🇭 · Hua-Sheng Shao🇫🇷

   The CERN LHC is not only the current energy-frontier collider for parton-parton collisions, but has proven a powerful photon collider providing photon-photon ($\gamma \gamma$) collisions at center-of-mass energies and luminosities never reached before. The latest theoretical developments implemented in the gamma-UPC Monte Carlo (MC) event generator, which can calculate arbitrary exclusive final state produced via $\gamma \gamma$ fusion in ultraperipheral collisions (UPCs) of protons and/or nuclei at the LHC, are presented. These include azimuthal modulations of dilepton pairs produced in the $\gamma \gamma \to {\ell }^{+}{\ell }^{-}$ process, and neutron emission probabilities for photoexcited lead ions in PbPb UPCs. A few comparisons of the results of the updated gamma-UPC v.1.6 code to relevant RHIC and LHC data are presented.

   ↳ hep-phhep-exnucl-exnucl-thPoS(2025)·5 citations
7. 07*

   New Insights into Supradense Matter from Dissecting Scaled Stellar Structure Equations

   Bao-Jun Cai🇨🇳 · Bao-An Li🇺🇸

   The strong-field gravity in General Relativity (GR) realized in neutron stars (NSs) renders the Equation of State (EOS) $P(\epsilon )$ of supradense neutron star (NS) matter to be essentially nonlinear and refines the upper bound for $\varphi \equiv P/\epsilon$ to be much smaller than the Special Relativity (SR) requirement with linear EOSs, where $P$ and $\epsilon$ are respectively the pressure and energy density of the system considered. Specifically, a tight bound $\varphi \lesssim 0.374$ is obtained by anatomizing perturbatively the intrinsic structures of the scaled Tolman--Oppenheimer--Volkoff (TOV) equations without using any input nuclear EOS. New insights gained from this novel analysis provide EOS-model independent constraints on properties (e.g., density profiles of the sound speed squared $s^2=\text{d}P/\text{d}\epsilon$ and trace anomaly $\Delta =1/3-\varphi$) of cold supradense matter in NS cores. Using the gravity-matter duality in theories describing NSs, we investigate the impact of gravity on supradense matter EOS in NSs. In particular, we show that the NS mass $M_{\mathrm{NS}}$, radius $R$ and its compactness $\xi \equiv M_{\mathrm{NS}}/R$ scale with certain combinations of its central pressure and energy density (encapsulating its central EOS). Thus, observational data on these properties of NSs can straightforwardly constrain NS central EOSs without relying on any specific nuclear EOS-model.

   ↳ astro-ph.HEastro-ph.GAhep-phnucl-ex+1Front.Astron.Space Sci.(2024)·4 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.