Thu·Dec 1, 2022Thursday·December 1, 2022

1. 01*

   Stellar $s$-process neutron capture cross sections of ${}^{69,71}$Ga

   M. Tessler · M. Paul🇮🇱 · S. Halfon · Y. Kashiv · D. Kijel · A. Kreisel🇮🇱 · A. Shor · L. Weissman

   The stable gallium isotopes, ${}^{69,71}$Ga, are mostly produced by the weak slow ($s$) process in massive stars. We report here on measurements of astrophysically-relevant neutron capture cross sections of the ${}^{69,71}$Ga$(n,\gamma )$ reactions. The experiments were performed by the activation technique using a high-intensity ($3-5\times 10^{10}$ n/s), quasi-Maxwellian neutron beam that closely mimics conditions of stellar $s$-process nucleosynthesis at $kT\approx$ 40 keV. The neutron field was produced by a mA proton beam at $E_p=1925$ keV (beam power of 2-3 kW) from the Soreq Applied Research Accelerator Facility (SARAF), bombarding the Liquid-Lithium Target (LiLiT). A 473 mg sample of Ga${}_2$O${}_3$ of natural isotopic composition was activated in the LiLiT neutron field and the activities of ${}^{70,72}$Ga were measured by decay counting via $\gamma$-spectrometry with a high-purity germanium detector. The Maxwellian-averaged cross sections at $kT$ = 30 keV of ${}^{69}$Ga and ${}^{71}$Ga determined in this work are 136(8) mb and 105(7) mb, respectively, in good agreement with previous experimental values. Astrophysical implications of the measurements are discussed.

   nucl-exPRC(2022)·2 citations
2. 02*

   Dissipative reactions with intermediate-energy beams -- a novel approach to populate complex-structure states in rare isotopes

   A. Gade🇺🇸 · B. A. Brown🇺🇸 · D. Weisshaar🇺🇸 · D. Bazin🇺🇸 · K. W. Brown🇺🇸 · R. J. Charity🇺🇸 · P. Farris · A. M. Hill · J. Li🇨🇳 · B. Longfellow🇺🇸 · D. Rhodes🇨🇦 · W. Reviol🇺🇸 · J. A. Tostevin🇬🇧

   A novel pathway for the formation of multi-particle-multi-hole (np-mh) excited states in rare isotopes is reported from highly energy- and momentum-dissipative inelastic-scattering events measured in reactions of an intermediate-energy beam of 38Ca on a Be target. The negative-parity,complex-structure final states in 38Ca were observed following the in-beam gamma-ray spectroscopy of events in the 9Be(38Ca,38Ca+gamma)X reaction in which the scattered projectile lost longitudinal momentum of order p = 700 MeV/c. The characteristics of the observed final states are discussed and found to be consistent with the formation of excited states involving the rearrangement of multiple nucleons in a single, highly-energetic projectile-target collision. Unlike the far-less dissipative, surface-grazing reactions usually exploited for the in-beam gamma-ray spectroscopy of rare isotopes, these more energetic collisions appear to offer a practical pathway to nuclear-structure studies of more complex multi-particle configurations in rare isotopes - final states conventionally thought to be out of reach with high-luminosity fast-beam-induced reactions.

   nucl-exnucl-thPRL(2022)·11 citations
3. 03*

   Observation of Directed Flow of Hypernuclei ${}_{\Lambda }^3$H and ${}_{\Lambda }^4$H in $\sqrt{s_{\mathrm{NN}}}$ = 3 GeV Au+Au Collisions at RHIC

   STAR Collaboration: B. E. Aboona · J. Adam · J. R. Adams · G. Agakishiev · I. Aggarwal · M. M. Aggarwal · Z. Ahammed · A. Aitbaev · I. Alekseev · D. M. Anderson · A. Aparin · J. Atchison and 342 other authors

   We report here the first observation of directed flow ($v_1$) of the hypernuclei ${}_{\Lambda }^3$H and ${}_{\Lambda }^4$H in mid-central Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 3 GeV at RHIC. These data are taken as part of the beam energy scan program carried out by the STAR experiment. From 165 $\times$ 10${}^6$ events in 5%-40% centrality, about 8400 ${}_{\Lambda }^3$H and 5200 ${}_{\Lambda }^4$H candidates are reconstructed through two- and three-body decay channels. We observe that these hypernuclei exhibit significant directed flow. Comparing to that of light nuclei, it is found that the midrapidity $v_1$ slopes of ${}_{\Lambda }^3$H and ${}_{\Lambda }^4$H follow baryon number scaling, implying that the coalescence is the dominant mechanism for these hypernuclei production in such collisions.

   nucl-exPRL(2023)·43 citations
4. 04*

   Medium Response and Jet-Hadron Correlations in Relativistic Heavy-Ion Collisions

   Shanshan Cao🇨🇳 · Guang-You Qin🇨🇳

   High-energy heavy-ion collisions at the Relativistic Heavy-Ion Collider and the Large Hadron Collider have evolved from qualitative understanding into precise extraction of the properties of the Quantum Chromodynamics medium at extremely high temperature. Jet quenching has offered unique insights into the transport properties of the Quark-Gluon Plasma (QGP) created in these energetic collisions. Apart from medium modification of jets, jet-induced medium excitation constitutes another crucial aspect of jet-QGP interaction, and is indispensable in understanding the soft components of jets. We review recent theoretical and phenomenological developments on medium response to jet energy loss, including an overview of both weakly and strongly coupled approaches for describing the thermalization and propagation of energy deposition from jets, effects of medium response on jet observables, and exploration of its unique signatures in jet-hadron correlations. Jet-induced medium excitation is shown to be an essential component in probing the in-medium dynamics of jets and a critical step towards precise extraction of the QGP properties.

   ↳ nucl-thhep-phnucl-exAnn.Rev.Nucl.Part.Sci.(2023)·39 citations
5. 05*

   Lifetime of the hypertriton

   D. Gazda🇨🇿 · A. Pérez-Obiol🇪🇸 · A. Gal🇮🇱 · E. Friedman🇮🇱

   Conflicting values of the hypertriton lifetime $\tau ({}_{\Lambda }^3\mathrm{H})$ were derived in relativistic heavy ion (RHI) collision experiments over the last decade. A very recent ALICE Collaboration measurement is the only experiment where the reported $\tau ({}_{\Lambda }^3\mathrm{H})$ comes sufficiently close to the free-$\Lambda$ lifetime ${\tau }_{\Lambda }$,as expected naively for a very weakly bound $\Lambda$ in ${}_{\Lambda }^3\mathrm{H}$. We revisited theoretically this ${}_{\Lambda }^3\mathrm{H}$ lifetime puzzle, using ${}_{\Lambda }^3\mathrm{H}$ and ${}^3\mathrm{He}$ wave functions computed within the abinitio no-core shell model employing interactions derived from chiral effective field theory to calculate the two-body decay rate $\Gamma ({}_{\Lambda }^3\mathrm{H}\to {}^3\mathrm{He}+{\pi }^{-})$. We found significant but opposing contributions arising from $\Sigma NN$ admixtures in ${}_{\Lambda }^3\mathrm{H}$ and from ${\pi }^{-}-{}^3\mathrm{He}$ final-state interaction. To derive $\tau ({}_{\Lambda }^3\mathrm{H})$, we evaluated the inclusive ${\pi }^{-}$ decay rate ${\Gamma }_{{\pi }^{-}}({}_{\Lambda }^3\mathrm{H})$ by using the measured branching ratio $\Gamma ({}_{\Lambda }^3\mathrm{H}\to {}^3\mathrm{He}+{\pi }^{-})/{\Gamma }_{{\pi }^{-}}({}_{\Lambda }^3\mathrm{H})$ and added the ${\pi }^0$ contributions through the $\Delta I=\frac{1}{2}$ rule. The resulting $\tau ({}_{\Lambda }^3\mathrm{H})$ varies strongly with the rather poorly known $\Lambda$ separation energy $E_{\mathrm{sep}}({}_{\Lambda }^3\mathrm{H})$ and it is thus possible to associate each one of the distinct RHI $\tau ({}_{\Lambda }^3\mathrm{H})$ measurements with its own underlying value of $E_{\mathrm{sep}}({}_{\Lambda }^3\mathrm{H})$.

   ↳ nucl-thhep-phnucl-exEPJ Web Conf.(2022)·1 citation
6. 06*

   Predicting Beta Decay Energy with Machine Learning

   Jose M. Munoz🇨🇴 · Serkan Akkoyun🇬🇧 · Zayda P. Reyes · Leonardo A. Pachon

   $Q_{\beta }$ represents one of the most important factors characterizing unstable nuclei, as it can lead to a better understanding of nuclei behavior and the origin of heavy atoms. Recently, machine learning methods have been shown to be a powerful tool to increase accuracy in the prediction of diverse atomic properties such as energies, atomic charges, volumes, among others. Nonetheless, these methods are often used as a black box not allowing unraveling insights into the phenomena under analysis. Here, the state-of-the-art precision of the $\beta$-decay energy on experimental data is outperformed by means of an ensemble of machine-learning models. The explainability tools implemented to eliminate the black box concern allowed to identify uncertainty and atomic number as the most relevant characteristics to predict $Q_{\beta }$ energies. Furthermore, physics-informed feature addition improved models' robustness and raised vital characteristics of theoretical models of the nuclear structure.

   ↳ nucl-thnucl-exphysics.data-anPRC(2023)·14 citations
7. 07*

   Vortex rings in heavy-ion collisions at energies $\sqrt{s_{NN}}=$ 3--30 GeV and possibility of their observation

   Yu. B. Ivanov🇷🇺

   The ring structures that appear in Au+Au collisions at collision energies $\sqrt{s_{NN}}=$ 3 -- 30 GeV are studied. The calculations are performed within the model of three-fluid dynamics. It is demonstrated that a pare of vortex rings are formed, one at forward and another at backward rapidities, in ultra-central Au+Au collisions at $\sqrt{s_{NN}}>$ 4 GeV. The vortex rings carry information about early stage of the collision, in particular about the stopping of baryons. It is shown that these rings can be detected by measuring the ring observable $R_{\Lambda }$ even in rapidity range $0<y<0.5$ (or $-0.5<y<0$) on the level of 0.5--1.5\% at $\sqrt{s_{NN}}=$ 5 -- 20 GeV. At forward/backward rapidities, the $R_{\Lambda }$ signal is expected to be stronger. Possibility of observation of the vortex-ring signal against background of non-collective transverse polarization is discussed.

   ↳ nucl-thhep-phnucl-exPRC(2023)·6 citations
8. 08*

   Probing the Mechanism of Neutrinoless Double-Beta Decay in Multiple Isotopes

   Matteo Agostini🇬🇧 · Frank F. Deppisch🇬🇧 · Graham Van Goffrier🇬🇧

   A large experimental program is being mounted to search for neutrinoless double-beta decay over the next decade. Multiple experiments using different target isotopes are being prepared to explore the whole parameter space allowed for inverted-ordered light neutrinos, and have the potential to make discoveries in several other scenarios, including normal-ordered light neutrinos and other exotic mechanisms. We investigate to what extent long-range and exotic short-range contributions may be distinguished by combining measurements of the decay half-life across isotopes. We demonstrate how measurements in two isotopes may facilitate a joint measurement up to a two-fold degeneracy, and how a further measurement in a third isotope may remove this degeneracy. We also highlight the precision of the nuclear matrix elements needed to convert half-lives into information on the underlying decay mechanism. Considering their correlations and uncertainties in the framework of a global Bayesian analysis, we assess the consequences of a possible future 10-fold reduction in uncertainties. Our work motivates an experimental program measuring neutrinoless double-beta decay in more than one isotope, as this would break parameter degeneracies and advance our understanding of particle physics beyond the Standard Model.

   ↳ hep-phhep-exnucl-exJHEP(2023)·19 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.