Mon·Feb 28, 2022Monday·February 28, 2022

1. 01*

   Impact of the Coulomb field on charged-pion spectra in few-GeV heavy-ion collisions

   J. Adamczewski-Musch🇸🇰 · O. Arnold🇩🇪 · C. Behnke🇩🇪 · A. Belounnas🇫🇷 · A. Belyaev🇷🇺 · J.C. Berger-Chen🇩🇪 · A. Blanco🇵🇹 · C. Blume🇩🇪 · M. Böhmer🇩🇪 · P. Bordalo🇵🇹 · S. Chernenko🇷🇺 · L. Chlad🇨🇿 and 115 other authors

   In nuclear collisions the incident protons generate a Coulomb field which acts on produced charged particles. The impact of these interactions on charged pion transverse-mass and rapidity spectra, as well as on pion-pion momentum correlations is investigated in Au+Au collisions at $\sqrt{s_{NN}}$ = 2.4 GeV. We show that the low-mt part of the data ($m_t<0.2$ GeV/c${}^2$) can be well described with a Coulomb-modified Boltzmann distribution that also takes changes of the Coulomb field during the expansion of the fireball into account. The observed centrality dependence of the fitted mean Coulomb potential deviates strongly from a $A_{part}^{2/3}$ scaling, indicating that, next to the fireball, the non-interacting charged spectators have to be taken into account. For the most central collisions, the Coulomb modifications of the HBT source radii are found to be consistent with the potential extracted from the single-pion transverse-mass distributions. This finding suggests that the region of homogeneity obtained from two-pion correlations coincides with the region in which the pions freeze-out. Using the inferred mean-square radius of the charge distribution at freeze-out, we have deduced a baryon density, in fair agreement with values obtained from statistical hadronization model fits to the particle yields.

   nucl-exEPJA(2022)·7 citations
2. 02*

   In-beam $\gamma$-ray spectroscopy of ${}^{32}$Mg via direct reactions

   N. Kitamura🇯🇵 · K. Wimmer🇯🇵 · T. Miyagi🇨🇦 · A. Poves🇪🇸 · N. Shimizu🇯🇵 · J. A. Tostevin🇬🇧 · V. M. Bader🇺🇸 · C. Bancroft🇺🇸 · D. Barofsky🇺🇸 · T. Baugher🇺🇸 · D. Bazin🇺🇸 · J. S. Berryman🇺🇸 and 17 other authors

   Background: The nucleus ${}^{32}$Mg ($N=20$ and $Z=12$) plays a central role in the so-called "island of inversion" where in the ground states $sd$-shell neutrons are promoted to the $fp$-shell orbitals across the shell gap, resulting in the disappearance of the canonical neutron magic number $N=20$. Purpose: The primary goals of this work are to extend the level scheme of ${}^{32}$Mg, provide spin-parity assignments to excited states, and discuss the microscopic structure of each state through comparisons with theoretical calculations. Method: In-beam $\gamma$-ray spectroscopy of ${}^{32}$Mg was performed using two direct-reaction probes, one-neutron (two-proton) knockout reactions on ${}^{33}$Mg (${}^{34}$Si). Final-state exclusive cross sections and parallel momentum distributions were extracted from the experimental data and compared with eikonal-based reaction model calculations combined with shell-model overlap functions. Results: Owing to the remarkable selectivity of the one-neutron and two-proton knockout reactions, a significantly updated level scheme for ${}^{32}$Mg, which exhibits negative-parity intruder and positive-parity normal states, was constructed. The experimental results were confronted with four different nuclear structure models. Conclusions: In some of these models, different aspects of ${}^{32}$Mg and the transition into the island of inversion are well described. However, unexplained discrepancies remain, and even with the help of these state-of-the-art theoretical approaches, the structure of this key nucleus is not yet fully captured.

   nucl-exnucl-thPRC(2022)·7 citations
3. 03*

   Precise Q value measurements of ${}^{112,113}$Ag and ${}^{115}$Cd with the Canadian Penning trap for evaluation of potential ultra-low Q value $\beta$-decays

   Nadeesha D. Gamage🇺🇸 · Rachel Sandler🇺🇸 · Fritz Buchinger🇨🇦 · Jason A. Clark · Dwaipayan Ray🇨🇦 · Rodney Orford🇨🇦 · William S. Porter🇨🇦 · Matthew Redshaw🇺🇸 · Guy Savard🇺🇸 · Kumar S. Sharma🇮🇳 · Adrian A. Valverde🇨🇦

   An ultra-low Q value $\beta$-decay can occur from a parent nuclide to an excited state in the daughter with $Q_{UL}$ <1 keV. These decays are of interest for nuclear $\beta$-decay theory and as potential candidates in neutrino mass determination experiments. To date, only one ultra-low Q value $\beta$-decay has been observed -- that of ${}^{115}$In with $Q_{\beta }$ = 147(10) eV. A number of other potential candidates exist, but improved mass measurements are necessary to determine if the decays are energetically allowed and, in fact, ultra-low. We performed precise $\beta$-decay Q value measurements of ${}^{112,113}$Ag and ${}^{115}$Cd and combined them with nuclear energy level data for the daughter isotopes to determine if the potential UL Q value $\beta$-decay branches of ${}^{112,113}$Ag and ${}^{115}$Cd are energetically allowed and <1 keV. The Canadian Penning Trap at ANL was used to measure the cyclotron frequency ratios of singly-charged ${}^{112,113}$Ag and ${}^{115}$Cd ions with respect to their daughters. From these measurements, the ground-state $\beta$-decay Q values were obtained. The ${}^{112}$Ag, ${}^{113}$Ag, and ${}^{115}$Cd $\beta$-decay Q values were measured to be 3990.16(22) keV, 2085.7(4.6) keV, and 1451.36(34) keV, respectively. These results were compared to energies of excited states in ${}^{112}$Cd at 3997.75(14) keV, ${}^{113}$Cd at 2015.6(2.5) and 2080(10) keV, and ${}^{115}$In at 1448.787(9) keV, resulting in $Q_{\text{UL}}$ values of --7.59(26) keV, 6(11) keV, and 2.57(34) keV, respectively. The potential UL Q value decays of ${}^{112}$Ag and ${}^{115}$Cd have been ruled out. ${}^{113}$Ag is still a possible candidate until a more precise measurement of the 2080(10) keV, 1/2${}^{+}$ state of ${}^{113}$Cd is available. In the course of this work we have found the ground state mass of ${}^{113}$Ag reported in the 2020AME to be lower than our measurement by 69(17) keV (a 4$\sigma$ discrepancy).

   nucl-exPRC(2022)·14 citations
4. 04*

   Physics Opportunities with PROSPECT-II

   M. Andriamirado🇺🇸 · A. B. Balantekin🇺🇸 · C. D. Bass🇺🇸 · D. E. Bergeron🇺🇸 · E. Bernard🇺🇸 · N. S. Bowden🇺🇸 · C. D. Bryan🇺🇸 · R. Carr🇺🇸 · T. Classen🇺🇸 · A. J. Conant🇺🇸 · G. Deichert🇺🇸 · A. Delgado🇺🇸 and 52 other authors

   The PROSPECT experiment has substantially addressed the original 'Reactor Antineutrino Anomaly' by performing a high-resolution spectrum measurement from an enriched compact reactor core and a reactor model-independent sterile neutrino oscillation search based on the unique spectral distortions the existence of eV${}^2$-scale sterile neutrinos would impart. But as the field has evolved, the current short-baseline (SBL) landscape supports many complex phenomenological interpretations, establishing a need for complementary experimental approaches to resolve the situation. While the global suite of SBL reactor experiments, including PROSPECT, have probed much of the sterile neutrino parameter space, there remains a large region above 1 eV${}^2$ that remains unaddressed. Recent results from BEST confirm the Gallium Anomaly, increasing its significance to $\sim 5\sigma$, with sterile neutrinos providing a possible explanation of this anomaly. Separately, the MicroBooNE exclusion of electron-like signatures causing the MiniBooNE low-energy excess does not eliminate the possibility of sterile neutrinos as an explanation. Focusing specifically on the future use of reactors as a neutrino source for beyond-the-standard-model physics and applications, higher-precision spectral measurements still have a role to play. These recent results have created a confusing landscape which requires new data to disentangle the seemingly contradictory measurements. To directly probe ${\overline{\nu }}_e$ disappearance from high $\Delta m^2$ sterile neutrinos, the PROSPECT collaboration proposes to build an upgraded and improved detector, PROSPECT-II. It features an evolutionary detector design which can be constructed and deployed within one year and have impactful physics with as little as one calendar year of data.

   ↳ hep-exnucl-ex4 citations
5. 05*

   Hadronization and Color Transparency

   Kai gallmeister🇩🇪 · Ulrich Mosel🇩🇪

   In this article we review our work on the production of hadrons in the nuclear environment. We work with a string-breaking model for the initial production of hadrons and with a quantum-kinetic transport model (GiBUU) to describe the final state interactions of the newly formed (pre)hadrons. The latter are determined both by the formation times and by the time-development of the hadron-hadron cross section. We first show that only a linear time-dependence is able to describe the available hadronization data. We then compare with detailed data from HERMES and JLAB; very good agreement is reached in all reactions studied without any tuning of parameters. We also repeat predictions of spectra for pions and kaons at JLAB@12GeV. We finally explain the absence of CT effects in the recent experiment on proton transparencies in quasielastic (QE) events on nuclei. We propose to look instead for CT effects on protons in semi-inclusive DIS (SIDIS) events.

   ↳ nucl-thhep-exhep-phnucl-exMDPI Physics(2022)·5 citations
6. 06*

   EXFOR-NSR PDF database: a system for nuclear knowledge preservation and data curation

   V.V. Zerkin🇦🇹 · B. Pritychenko🇺🇸 · J. Totans · L. Vrapcenjak · A. Rodionov · G.I. Shulyak

   Current needs of nuclear science and technology include complete, well-documented, and easily verifiable nuclear data. The complete data records require supporting nuclear bibliography, presently stored in dedicated libraries, in addition, to actual data. Experimental nuclear reaction data (EXFOR) and Nuclear Science References (NSR) databases contain compilations based on primary (journals) and secondary (conference proceedings, theses, preprints, etc.) publications, and data received from authors via private communications. The secondary library materials and private communications often represent a bottleneck for nuclear data verification, compilation, evaluation, and dissemination activities. To address this issue, bibliographic materials were scanned into PDF (Portable Document Format) files and uploaded in a relational database. The traditional scope of nuclear databases that includes meta-data and numbers derived from data in specialized formats was broadened to accommodate the large volumes of original nuclear data publications. The complete PDF publication files were stored in a relational database as Binary Large OBjects (BLOB). This unique collection of nuclear data compilations and supporting publications generate many opportunities for machine learning applications.

   ↳ physics.data-annucl-exJINST(2022)·3 citations
7. 07*

   Theia: Summary of physics program. Snowmass White Paper Submission

   M. Askins · Z. Bagdasarian · N. Barros · E.W. Beier · A. Bernstein · E. Blucher · R. Bonventre · E. Bourret · E. J. Callaghan · J. Caravaca · M. Diwan · S.T. Dye and 75 other authors

   Theia would be a novel, "hybrid" optical neutrino detector, with a rich physics program. This paper is intended to provide a brief overview of the concepts and physics reach of Theia. Full details can be found in the Theia white paper [1].

   ↳ hep-exastro-ph.IMnucl-ex20 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.