Tue·Jun 25, 2024Tuesday·June 25, 2024

1. 01*

   Measurement of the ${}^{12}\mathrm{C}(e,e^{\prime })$ cross sections at $Q^2=0.8{\mathrm{GeV}}^2/c^2$

   M. Mihovilovič🇸🇮 · L. Doria🇩🇪 · P. Achenbach🇺🇸 · A. M. Ankowski🇵🇱 · S. Bacca🇩🇪 · D. Bosnar🇭🇷 · A. Denig🇩🇪 · M. O. Distler🇩🇪 · A. Esser🇩🇪 · I. Friščić🇭🇷 · C. Giusti🇮🇹 · M. Hoek🇩🇪 and 13 other authors

   We present the findings of a study based on a new inelastic electron-scattering experiment on the ${}^{12}\mathrm{C}$ nucleus focusing on the kinematic region of $Q^2=0.8{\mathrm{GeV}}^2/c^2$. The measured cross section is sensitive to the transverse response function and provides a stringent test of theoretical models, as well as of the theoretical assumptions made in Monte-Carlo event-generator codes developed for the interpretation of neutrino-nucleus experiments, such as DUNE and HyperK. We find that modern generators such as GENIE and GiBUU reproduce our new experimental data within 10$\%$.

   nucl-exnucl-thFew Body Syst.(2024)·11 citations
2. 02*

   Characterization of isomers produced by the spontaneous fission of ${}^{252}$Cf with the VESPA setup

   V. Piau (1 and 2)🇫🇷 · A. Göök (3)🇸🇪 · S. Oberstedt (4)🇧🇪 · A. Oberstedt (5)🇷🇴 · A. Chebboubi (1)🇫🇷 · O. Litaize (1)🇫🇷 · M. Vidali (4) ((1) CEA, DES, IRESNE, DER, Cadarache F-13108 Saint-Paul-Lez-Durance, France, (2) Université Paris-Saclay, CNRS/IN2P3, IJCLab, 91405 Orsay, France, (3) Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden, (4) European Commission, Joint Research Centre, Directorate for Nuclear Safety and Security, 2440 Geel, Belgium, (5) Extreme Light Infrastructure - Nuclear Physics (ELI-NP), Horia Hulubei National Institute for Physics and Nuclear Engineering (IFIN-HH), 077125 Bucharest-Magurele, Romania)🇧🇪

   Isomers produced by spontaneous fission of ${}^{252}$Cf have been measured with the VESPA setup, composed of LaBr${}_3$(Ce) detectors for fast $\gamma$-ray spectroscopy and an ionization chamber for detecting fission fragments. Identification of the isomers was derived from fission fragment-$\gamma$-$\gamma$ coincidences. This paper presents the half-life of 34 isomeric states measured with this setup, from less than the nanosecond up to tens of microseconds. Two of these isomers are reported for the first time, in ${}^{108}$Tc and ${}^{147}$Ce. In addition to this half-life analysis, the isomers are used to develop and test a nuclear charge calibration of the ionization chamber.

   nucl-exEPJA(2025)·2 citations
3. 03*

   Measurement of directed flow in Au+Au collisions at $\sqrt{s_{NN}}=$ 19.6 and 27 GeV with the STAR Event Plane Detector

   STAR Collaboration

   In heavy-ion collision experiments, the global collectivity of final-state particles can be quantified by anisotropic flow coefficients ($v_n$). The first-order flow coefficient, also referred to as the directed flow ($v_1$), describes the collective sideward motion of produced particles and nuclear fragments in heavy-ion collisions. It carries information on the very early stage of the collision, especially at large pseudorapidity ($\eta$), where it is believed to be generated during the nuclear passage time. Directed flow therefore probes the onset of bulk collective dynamics during thermalization, providing valuable experimental guidance to models of the pre-equilibrium stage. In 2018, the Event Plane Detector (EPD) was installed in STAR and used for the Beam Energy Scan phase-II (BES-II) data taking. The combination of EPD ($2.1<|\eta |<5.1$) and high-statistics BES-II data enables us to extend the $v_1$ measurement to the forward and backward $\eta$ regions. In this paper, we present the measurement of $v_1$ over a wide $\eta$ range in Au+Au collisions at $\sqrt{s_{NN}}=$ 19.6 and 27 GeV using the STAR EPD. The results of the analysis at $\sqrt{s_{NN}}=$19.6 GeV exhibit excellent consistency with the previous PHOBOS measurement, while elevating the precision of the overall measurement. The increased precision of the measurement also revealed finer structures in heavy-ion collisions, including a potential observation of the first-order event-plane decorrelation. Multiple physics models were compared to the experimental results. Only a transport model and a three-fluid hybrid model can reproduce a sizable $v_1$ at large $\eta$ as was observed experimentally. The model comparison also indicates $v_1$ at large $\eta$ might be sensitive to the QGP phase transition.

   nucl-exPRC(2025)·5 citations
4. 04*

   Impact of reactor neutrino uncertainties on coherent scattering's discovery potential

   Leendert Hayen🇫🇷

   Nuclear power reactors are the most intense man-made source of antineutrino's and have long been recognized as promising sources for coherent elastic neutrino-nucleus scattering (CE$\nu$NS) studies. Its observation and the spectral shape of the associated recoil spectrum is sensitive to a variety of exotic new physics scenarios and many experimental efforts are underway. Within the context of the reactor antineutrino anomaly, which initially indicated eV-scale sterile neutrino's, the modeling of the reactor antineutrino spectrum has seen a significant evolution in the last decade. Even so, uncertainties remain due to a variety of nuclear structure effects, incomplete information in nuclear databases and fission dynamics complexities. Here, we investigate the effects of these uncertainties on one's ability to accurately distinguish new physics signals. For the scenarios discussed here, we find that reactor spectral uncertainties are similar in magnitude to the projected sensitivities pointing towards a need for $\beta$ spectroscopy measurements below the inverse $\beta$ decay threshold.

   ↳ nucl-thhep-phnucl-exJ.Phys.G(2025)·3 citations
5. 05*

   Monopole Excitation and Nuclear Compressibility: Present and Future Perspectives

   J. C. Zamora🇺🇸 · S. Giraud🇫🇷

   Isoscalar giant resonances are nuclear collective excitations associated with the oscillation in phase of protons and neutrons according to a certain multipolarity $L$. In particular, the isoscalar giant monopole resonance ($L=0$) is the strongest nuclear compression mode, and its excitation energy is directly related to the compression modulus for finite nuclei. Typically, microscopic calculations are utilized to establish a relationship between the experimental compression modulus and the nuclear incompressibility that is a crucial parameter of the equation of state for nuclear matter. The incompressibility of nuclear matter has been determined with an accuracy of 10 to 20\% using relativistic and non-relativistic microscopic models for describing the monopole distributions in ${}^{208}$Pb and ${}^{90}$Zr isotopes. However, the same theoretical models are not able to describe data for open-shell nuclei, such as those of tin and cadmium isotopes. In fact, only effective interactions with a softer nuclear-matter incompressibility are able to predict the centroid energy of monopole distributions for open-shell nuclei. An unified description of the monopole resonance in ${}^{208}$Pb and other open-shell nuclei remains unsolved from the theory side. Most of this uncertainty is due to our poor knowledge of the symmetry energy, which is another essential component of the equation of state of nuclear matter. Therefore, new experimental data along isotopic chains covering a wide range in $N/Z$ ratios, including neutron-deficient and neutron-rich nuclei, are of paramount importance for determining both the nuclear-matter incompressibility and the symmetry energy more precisely.

   ↳ nucl-thastro-ph.HEnucl-ex2 citations
6. 06*

   Comments on the publication "Discrete symmetries tested at 10e-4 precision using linear polarization of photons from positronium annihilations" by P. Moskal et al

   E.A. George🇺🇸 · T.E. Haugen🇺🇸 · O. Naviliat-Cuncic🇫🇷 · P.A. Voytas🇺🇸

   The authors of Ref.[1] (referred to here as "Moskal et al.") claim to have performed the most precise test of P, T and CP invariance in the decay of ortho-Positronium. In this note: 1) we demonstrate, assuming standard properties for Compton scattering, that the average value of the correlation measured by Moskal et al. must necessarily be zero, independently of any physics occurring in o-Ps decay; 2) we point out that there is no formal justification to equate the normal vector to the Compton scattering plane with the incident photon polarization, as done by Moskal et al.; 3) we observe the absence of characterization of the device as a Compton polarimeter, which is paramount in photon polarimetry; 4) we review previous measurements of the polarization of photons from o-Ps decay, properly implementing the Compton polarimetry technique, and make the connection with tests of discrete symmetries; and 5) we stress that the correlation proposed by Moskal et al. cannot be generated solely by the physics of o-Ps decay, including possible violations of discrete symmetries.

   ↳ hep-phhep-exnucl-ex1 citation
7. 07*

   Revisiting the nuclear magnetic octupole moment

   Stavros Bofos🇫🇷 · Theo J. Mertzimekis🇬🇷

   The nuclear magnetic octupole moment is revisited as a potentially useful observable for nuclear structure studies. The magnetic octupole moment, $\Omega$, is examined in terms of the nuclear collective model including weak and strong coupling. Single-particle formulation is additionally considered in the overall comparison of theoretical predictions with available experimental data. Mirror nuclei symmetry is examined in terms of the magnetic octupole moment isoscalar and isovector terms. A full list of predictions for $\Omega$ of odd-proton and odd-neutron nuclei in medium-heavy mass regimes of the nuclear chart is produced aiming at providing starting values for future experimental endeavors.

   ↳ nucl-thnucl-exAtom.Data Nucl.Data Tabl.(2024)·2 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.