Thu·Apr 27, 2023Thursday·April 27, 2023

1. 01*

   Precision Spectroscopy of Fast, Hot Exotic Isotopes Using Machine Learning Assisted Event-by-Event Doppler Correction

   Silviu-Marian Udrescu🇺🇸 · Diego Alejandro Torres · Ronald Fernando Garcia Ruiz🇺🇸

   We propose an experimental scheme for performing sensitive, high-precision laser spectroscopy studies on fast exotic isotopes. By inducing a step-wise resonant ionization of the atoms travelling inside an electric field and subsequently detecting the ion and the corresponding electron, time- and position-sensitive measurements of the resulting particles can be performed. Using a Mixture Density Network (MDN), we can leverage this information to predict the initial energy of individual atoms and thus apply a Doppler correction of the observed transition frequencies on an event-by-event basis. We conduct numerical simulations of the proposed experimental scheme and show that kHz-level uncertainties can be achieved for ion beams produced at extreme temperatures ($>10^8$ K), with energy spreads as large as $10$ keV and non-uniform velocity distributions. The ability to perform in-flight spectroscopy, directly on highly energetic beams, offers unique opportunities to studying short-lived isotopes with lifetimes in the millisecond range and below, produced in low quantities, in hot and highly contaminated environments, without the need for cooling techniques. Such species are of marked interest for nuclear structure, astrophysics, and new physics searches.

   nucl-excs.AIcs.LGphysics.atom-ph+1PRResearch(2024)·3 citations
2. 02*

   Two-proton emission and related phenomena

   Marek Pfützner🇵🇱 · Ivan Mukha🇩🇪 · Simin Wang🇨🇳

   One of characteristic phenomena for nuclei beyond the proton dripline is the simultaneous emission of two protons (2\emph{p}). The current status of our knowledge of this most recently observed and the least known decay mode is presented. First, different approaches to theoretical description of this process, ranging from effective approximations to advanced three-body models are overviewed. Then, after a brief survey of main experimental methods to produce 2\emph{p}-emitting nuclei and techniques to study their decays, experimental findings in this research field are presented and discussed. This review covers decays of short-lived resonances and excited states of unbound nuclei as well as longer-lived, ground-state radioactive decays. In addition, more exotic decays like three- and four-proton emission are addressed. Finally, related few-body topics, like two-neutron and four-neutron radioactivity, and the problem of the tetraneutron are shortly discussed.

   nucl-exnucl-thPPNP(2023)·51 citations
3. 03*

   Determination of the moments of the proton charge density

   M. Atoui🇫🇷 · M.B. Barbaro🇮🇹 · M. Hoballah🇫🇷 · C. Keyrouz🇫🇷 · M. Lassaut🇫🇷 · D. Marchand🇫🇷 · G. Quéméner🇫🇷 · E. Voutier🇫🇷

   A global analysis of proton electric form factor experimental data from Rosenbluth separation and low squared four-momentum transfer experiments is discussed for the evaluation of the spatial moments of the proton charge density based on the recently published integral method. Specific attention is paid to the evaluation of the systematic errors of the method, particularly the sensitivity to the choice of the mathematical expression of the form factor fitting function. Within this comprehensive analysis of proton electric form factor data, the moments of the proton charge density are determined for integer order moments, particularly: $⟨r^2⟩$=0.694(09)${}_{Sta.}$(16)${}_{Sys.}$~fm${}^2$, $⟨r^3⟩$=0.870(46)${}_{Sta.}$(80)${}_{Sys.}$~fm${}^3$, and $⟨r^4⟩$=1.47(25)${}_{Sta.}$(45)${}_{Sys.}$~fm${}^4$.

   nucl-exnucl-thPRC(2024)·5 citations
4. 04*

   Li${}_2$${}^{100\text{depl}}$MoO${}_4$ Scintillating Bolometers for Rare-Event Search Experiments

   I.C. Bandac🇪🇸 · A.S. Barabash🇷🇺 · L. Bergé🇫🇷 · Yu.A. Borovlev🇷🇺 · J.M. Calvo-Mozota🇪🇸 · P. Carniti🇮🇹 · M. Chapellier🇫🇷 · I. Dafinei🇮🇹 · F.A. Danevich🇺🇦 · L. Dumoulin🇫🇷 · F. Ferri🇫🇷 · A. Giuliani🇫🇷 and 26 other authors

   We report on the development of scintillating bolometers based on lithium molybdate crystals containing molybdenum depleted in the double-$\beta$ active isotope ${}^{100}$Mo (Li${}_2$${}^{100\text{depl}}$MoO${}_4$). We used two Li${}_2$${}^{100\text{depl}}$MoO${}_4$ cubic samples, 45 mm side and 0.28 kg each, produced following purification and crystallization protocols developed for double-$\beta$ search experiments with ${}^{100}$Mo-enriched Li${}_2$MoO${}_4$ crystals. Bolometric Ge detectors were utilized to register scintillation photons emitted by the Li${}_2$${}^{100\text{depl}}$MoO${}_4$ crystal scintillators. The measurements were performed in the CROSS cryogenic set-up at the Canfranc underground laboratory (Spain). We observed that the Li${}_2$${}^{100\text{depl}}$MoO${}_4$ scintillating bolometers are characterized by excellent spectrometric performance ($\sim$3--6 keV FWHM at 0.24--2.6 MeV $\gamma$'s), moderate scintillation signal ($\sim$0.3--0.6 keV/MeV depending on light collection conditions) and high radiopurity (${}^{228}$Th and ${}^{226}$Ra activities are below a few $\mu$Bq/kg), comparable to the best reported results of low-temperature detectors based on Li${}_2$MoO${}_4$ with natural or ${}^{100}$Mo-enriched molybdenum content. Prospects of Li${}_2$${}^{100\text{depl}}$MoO${}_4$ bolometers for use in rare-event search experiments are briefly discussed.

   ↳ physics.ins-detnucl-exSensors(2023)·11 citations
5. 05*

   Machine learning method for ${}^{12}$C event classification and reconstruction in the active target time-projection chamber

   Huangkai Wu · Youjing Wang · Yumiao Wang · Xiangai Deng · Xiguang Cao · Deqing Fang · Weihu Ma · Hongwei Wang · Wanbing He · Changbo Fu · Yugang Ma

   Active target time projection chambers are important tools in low energy radioactive ion beams or gamma rays related researches. In this work, we present the application of machine learning methods to the analysis of data obtained from an active target time projection chamber. Specifically, we investigate the effectiveness of Visual Geometry Group (VGG) and the Residual neural Network (ResNet) models for event classification and reconstruction in decays from the excited $2_2^{+}$ state in ${}^{12}$C Hoyle rotation band. The results show that machine learning methods are effective in identifying ${}^{12}$C events from the background noise, with ResNet-34 achieving an impressive precision of 0.99 on simulation data, and the best performing event reconstruction model ResNet-18 providing an energy resolution of ${\sigma }_E<77$ keV and an angular reconstruction deviation of ${\sigma }_{\theta }<0.1$ rad. The promising results suggest that the ResNet model trained on Monte Carlo samples could be used for future classifying and predicting experimental data in active target time projection chambers related experiments.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2023)·12 citations
6. 06*

   Neutron-proton effective mass splitting in neutron-rich matter

   Sibo Wang🇨🇳 · Hui Tong🇩🇪 · Qiang Zhao🇰🇷 · Chencan Wang🇨🇳 · Peter Ring🇩🇪 · Jie Meng🇨🇳

   Nucleon effective masses in neutron-rich matter are studied with the relativistic Brueckner-Hartree-Fock (RBHF) theory in the full Dirac space. The neutron and proton effective masses for symmetric nuclear matter are 0.80 times rest mass, which agrees well with the empirical values. In neutron-rich matter, the effective mass of the neutron is found larger than that of the proton, and the neutron-proton effective mass splittings at the empirical saturation density are predicted as $0.187\alpha$ with $\alpha$ being the isospin asymmetry parameter. The result is compared to other ab initio calculations and is consistent with the constraints from the nuclear reaction and structure measurements, such as the nucleon-nucleus scattering, the giant resonances of ${}^{208}$Pb, and the Hugenholtz-Van Hove theorem with systematics of nuclear symmetry energy and its slope. The predictions of the neutron-proton effective mass splitting from the RBHF theory in the full Dirac space might be helpful to constrain the isovector parameters in phenomenological density functionals.

   ↳ nucl-thnucl-exPRC(2023)·21 citations
7. 07*

   On Sequential Single-Pion Production in Double-Pionic Fusion

   M. Bashkanov🇬🇧 · H. Clement🇩🇪

   Recently a two-step process has been proposed for the double-pionic fusion to deuterium $pn(I=0)\to d{\pi }^{+}{\pi }^{-}$. Its calculation is solely based on total cross section data for the two sequential single-pion production steps $pn(I=0)\to pp{\pi }^{-}$ followed by $pp\to d{\pi }^{+}$. Though this sequential process was aimed to explain the dibaryon resonance $d^{\ast }(2380)$ peak in double-pionic fusion, we demonstrate that this is not the case. It rather fits to a possible broad bump at 2.31 GeV in the energy dependence of the $pn\to d{\pi }^0{\pi }^0$ reaction, which was recently interpreted as a consequence of dibaryonic excitations in isoscalar single-pion production.

   ↳ nucl-thhep-exhep-phnucl-exNPA(2023)·0 citations
8. 08*

   Portable neutron/gamma scintillation detector for status monitoring of accelerator-driven neutron source IREN

   S. Nuruyev · D. Berikov · R. Akbarov · G. Ahmadov · F. Ahmadov · A. Sadigov · M. Holik · J. Naghiyev · A. Madadzada · K. Udovichenko

   Accelerator-driven system (ADS) facilities world-wide opens new opportunities for nuclear physics investigations, so that a high flux of neutrons through spallation reactions can be produced at these facilities. It is known that the measurement, continuous monitoring and optimization of the particle accelerator beam intensity are among the most important actions in the operation of such facilities. Considering this point of view, this paper presents a neutron/gamma counter based on a micropixel avalanche photodiode (MAPD) and a plastic scintillator that monitors the status of the accelerator-driven intense resonance neutron source (IREN) facility by measuring the neutron-gamma intensity in the target hall. The electronics of the modular neutron counter has been designed and developed, including a bias voltage source (up to 130 V), a preamplifier (36 gain) and discriminator (>10 mV) circuit. The last product of MAPD (operation voltage- 55 V, PDE- 33 %, total number of pixels- 136900) was used as a photon readout from a plastic scintillator. The sensitive area of MAPD was 3.7*3.7 mm2 and the size of the plastic scintillator 3.7*3.7*30 mm3. The measurement was carried out in the IREN target hall, where it was necessary to monitor not only high neutron fluxes, but also gamma quanta. The experimental results demonstrated a dependence between the count rate of the detector and the frequency of the accelerator, which ranges from 2 to 50 Hz.

   ↳ physics.ins-detnucl-ex0 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.