Wed·Jul 10, 2024Wednesday·July 10, 2024

1. 01*

   Measurement and analysis of the ${}^{246}$Cm and ${}^{248}$Cm neutron capture cross-sections at the EAR2 of the n TOF facility

   V. Alcayne · A. Kimura · E. Mendoza · D. Cano-Ott · O. Aberle · F. Álvarez-Velarde · S. Amaducci · J. Andrzejewski · L. Audouin · V. Bécares · V. Babiano-Suarez · M. Bacak and 121 other authors

   The ${}^{246}$Cm(n,$\gamma$) and ${}^{248}$Cm(n,$\gamma$) cross-sections have been measured at the Experimental Area 2 (EAR2) of the n_TOF facility at CERN with three C${}_6$D${}_6$ detectors. This measurement is part of a collective effort to improve the capture cross-section data for Minor Actinides (MAs), which are required to estimate the production and transmutation rates of these isotopes in light water reactors and innovative reactor systems. In particular, the neutron capture in ${}^{246}$Cm and ${}^{248}$Cm open the path for the formation of other Cm isotopes and heavier elements such as Bk and Cf and the knowledge of (n,$\gamma$) cross-sections of these Cm isotopes plays an important role in the transport, transmutation and storage of the spent nuclear fuel. The reactions ${}^{246}$Cm(n,$\gamma$) and ${}^{248}$Cm(n,$\gamma$) have been the two first capture measurements analyzed at n_TOF EAR2. Until this experiment and two recent measurements performed at J-PARC, there was only one set of data of the capture cross-sections of ${}^{246}$Cm and ${}^{248}$Cm, that was obtained in 1969 in an underground nuclear explosion experiment. In the measurement at n_TOF a total of 13 resonances of ${}^{246}$Cm between 4 and 400 eV and 5 of ${}^{248}$Cm between 7 and 100 eV have been identified and fitted. The radiative kernels obtained for ${}^{246}$Cm are compatible with JENDL-5, but some of them are not with JENDL-4, which has been adopted by JEFF-3.3 and ENDF/B-VIII.0. The radiative kernels obtained for the first three ${}^{248}$Cm resonances are compatible with JENDL-5, however, the other two are not compatible with any other evaluation and are 20% and 60% larger than JENDL-5.

   nucl-exEPJA(2024)·3 citations
2. 02*

   Disentangling sources of momentum fluctuations in Xe+Xe and Pb+Pb collisions with the ATLAS detector

   ATLAS Collaboration

   High-energy nuclear collisions create a quark-gluon plasma, whose initial condition and subsequent expansion vary from event to event, impacting the distribution of the event-wise average transverse momentum ($P([p_{\mathrm{T}}])$). Distinguishing between contributions from fluctuations in the size of the nuclear overlap area (geometrical component) and other sources at fixed size (intrinsic component) presents a challenge. Here, these two components are distinguished by measuring the mean, variance, and skewness of $P([p_{\mathrm{T}}])$ in ${}^{208}$Pb+${}^{208}$Pb and ${}^{129}$Xe+${}^{129}$Xe collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ and 5.44 TeV, respectively, using the ATLAS detector at the LHC. All observables show distinct changes in behavior in ultra-central collisions, where the geometrical variations are suppressed as the overlap area reaches its maximum. These results demonstrate a new technique to disentangle geometrical and intrinsic fluctuations, enabling constraints on initial condition and properties of the quark-gluon plasma, such as the speed of sound.

   nucl-exhep-exPRL(2024)·39 citations
3. 03*

   White Paper on Polarized Target Studies with Real Photons in Hall D

   F. Afzal🇩🇪 · M. M. Dalton🇺🇸 · A. Deur🇺🇸 · P. Hurck🇬🇧 · C.D. Keith🇺🇸 · V. Mathieu🇪🇸 · S. Sirca🇸🇮 · Z. Yu🇺🇸

   This white paper summarizes the Workshop on Polarized Target Studies with Real Photons in Hall D at Jefferson Lab, that took place on 21 February 2024. The Workshop included about 45 participants both online and in person at Florida State University in Tallahassee. Contributions describe the experimental infrastructure available in Hall D and potential physics applications. The rate and detection capabilities of Hall D are outlined, as well as the properties of a circularly polarized photon beam and a polarized target. Possible physics measurements include light and strange quark baryon spectroscopy, the GDH sum rule, proton structure accessed through measurement of Generalized Parton Distributions and modification of nucleon structure within the nuclear medium.

   nucl-ex4 citations
4. 04*

   Antiproton annihilation at rest in thin solid targets and comparison with Monte Carlo simulations

   Claude Amsler🇦🇹 · Horst Breuker🇯🇵 · Marcus Bumbar🇨🇭 · Matti Cerwenka🇦🇹 · Giovanni Costantini🇮🇹 · Rafael Ferragut🇮🇹 · Markus Fleck🇦🇹 · Marco Giammarchi🇮🇹 · Angela Gligorova🇦🇹 · Giulia Gosta🇮🇹 · Eric David Hunter🇦🇹 · Carina Killian🇦🇹 and 24 other authors

   The mechanism of antiproton-nucleus annihilation at rest is not fully understood, despite substantial previous experimental and theoretical work. In this study we used slow extracted antiprotons from the ASACUSA apparatus at CERN to measure the charged particle multiplicities and their energy deposits from antiproton annihilations at rest on three different nuclei: carbon, molybdenum and gold. The results are compared with predictions from different models in the simulation tools Geant4 and FLUKA. A model that accounts for all the observed features is still missing, as well as measurements at low energies, to validate such models.

   nucl-exEPJA(2024)·15 citations
5. 05*

   A Neutron Spectrometry for Fusion Plasmas

   Iskender Atilla Reyhancan

   It is very important to measure the plasma performances of fusion reactors such as fuel ion density, plasma temperature, fusion power, fast neutron energy, and neutron flux. Various diagnostic systems are needed to measure fast neutron properties in fusion plasmas. Generally, various types of neutron cameras and monitors are used. These systems are sensitive to neutron as well as gamma-ray radiation. Therefore, monitor systems that distinguish between neutron and gamma rays should be used. In this study, the NE-213 liquid scintillation detector was selected, and Pulse Shape Discriminator (PSD) NIM unit was used for the neutron/gamma-ray discrimination. True spectrum was found by unfolding the spectrum obtained by the reaction of neutrons to the protons in the detector with the FERD-PC computer code. In this study, the energy spectrum of fast neutrons produced in a neutron generator was measured by the unfolding method.

   nucl-exphysics.ins-det0 citations
6. 06*

   Net-Proton Number Cumulants in Strongly and Weakly Coupled QGP

   Kiminad A. Mamo🇺🇸

   We provide a description of the QCD phase diagram across different energy regimes. Without any adjustable free parameters fitted to lattice or experimental data, we demonstrate that the net-proton number cumulant ratios from the Beam Energy Scan-I (BES-I) central ($0-5\%$) Au+Au collision experiments at RHIC, for center-of-mass energies $\sqrt{s}\ge 39\text{GeV}$, are well described by the $\text{dynamical soft-wall}$ AdS black hole model, indicating the formation of a strongly coupled quark-gluon plasma (sQGP) dominated by gluons in the large $N_c$ limit. We identify a critical point at ${\mu }_B=247\text{MeV}$ or $\sqrt{s}=16\text{GeV}$ in this model, where net-proton cumulant ratios show non-monotonic variation. However, for $\sqrt{s}<39\text{GeV}$, the recent BES-II data does not exhibit the expected variation due to the critical point, suggesting instead a transition to a nearly-cold (${\mu }_B\gg T$) weakly coupled QGP (wQGP), for $\sqrt{s}<7.7\text{GeV}$, dominated by valence quarks. This prediction can be tested by the upcoming STAR Fixed-Target experimental data.

   ↳ hep-phhep-thnucl-exnucl-th1 citation
7. 07*

   Constraining the dense matter equation of state with new NICER mass-radius measurements and new chiral effective field theory inputs

   Nathan Rutherford🇺🇸 · Melissa Mendes🇩🇪 · Isak Svensson🇩🇪 · Achim Schwenk🇩🇪 · Anna L. Watts🇳🇱 · Kai Hebeler🇩🇪 · Jonas Keller🇩🇪 · Chanda Prescod-Weinstein🇺🇸 · Devarshi Choudhury🇳🇱 · Geert Raaijmakers🇳🇱 · Tuomo Salmi🇳🇱 · Patrick Timmerman🇳🇱 and 3 other authors

   Pulse profile modeling of X-ray data from NICER is now enabling precision inference of neutron star mass and radius. Combined with nuclear physics constraints from chiral effective field theory ($\chi$EFT), and masses and tidal deformabilities inferred from gravitational wave detections of binary neutron star mergers, this has lead to a steady improvement in our understanding of the dense matter equation of state (EOS). Here we consider the impact of several new results: the radius measurement for the 1.42$M_{\odot }$ pulsar PSR J0437$-$4715 presented by Choudhury et al. (2024), updates to the masses and radii of PSR J0740$+$6620 and PSR J0030$+$0451, and new $\chi$EFT results for neutron star matter up to 1.5 times nuclear saturation density. Using two different high-density EOS extensions -- a piecewise-polytropic (PP) model and a model based on the speed of sound in a neutron star (CS) -- we find the radius of a 1.4$M_{\odot }$ (2.0$M_{\odot }$) neutron star to be constrained to the 95% credible ranges $12.28_{-0.76}^{+0.50}$km ($12.33_{-1.34}^{+0.70}$km) for the PP model and $12.01_{-0.75}^{+0.56}$km ($11.55_{-1.09}^{+0.94}$km) for the CS model. The maximum neutron star mass is predicted to be $2.15_{-0.16}^{+0.14}$$M_{\odot }$ and $2.08_{-0.16}^{+0.28}$$M_{\odot }$ for the PP and CS model, respectively. We explore the sensitivity of our results to different orders and different densities up to which $\chi$EFT is used, and show how the astrophysical observations provide constraints for the pressure at intermediate densities. Moreover, we investigate the difference $R_{2.0}-R_{1.4}$ of the radius of 2$M_{\odot }$ and 1.4$M_{\odot }$ neutron stars within our EOS inference.

   ↳ astro-ph.HEastro-ph.SRnucl-exnucl-thApJL(2024)·122 citations
8. 08*

   A Method to Constrain Preferential Emission and Spectator Dynamics in Heavy-Ion Collisions

   Vipul Bairathi🇨🇱 · Somadutta Bhatta🇺🇸

   Longitudinal particle production in heavy-ion collisions is influenced both by preferential emission from participating nucleons and by the breakup of spectator matter, yet quantifying these effects experimentally remains challenging. We introduce a Pearson correlation between spectator and charged-particle forward-backward asymmetries as an experimental probe of these phenomena. Using Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV simulated with A Multi-Phase Transport (AMPT) model, we validate that this correlator provides a robust, pseudorapidity-differential measure of the influence of preferential emission on the longitudinal structure of particle production. We further demonstrate that the correlation strength is sensitive to fluctuations in spectator number, which in experiments arise from evaporation and fragmentation of the spectator remnants. The proposed observable therefore offers a data-driven handle for constraining models of preferential emission and spectator breakup, thereby improving our understanding of the mechanisms that shape the final-state longitudinal distributions in heavy-ion collisions.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2026)·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.