Thu·Oct 29, 2020Thursday·October 29, 2020

1. 01*

   Manifestation of the Berry phase in the atomic nucleus ${}^{213}$Pb

   J.J. Valiente-Dobón · A. Gottardo · G. Benzoni · A. Gadea · S. Lunardi · A. Algora · G. de Angelis · D. Bazzacco · J. Benlliure · P. Boutachkov · A. Bracco · A.M. Bruce and 48 other authors

   The neutron-rich ${}^{213}$Pb isotope was produced in the fragmentation of a primary 1 GeV $A$ ${}^{238}$U beam, separated in FRS in mass and atomic number, and then implanted for isomer decay $\gamma$-ray spectroscopy with the RISING setup at GSI. A newly observed isomer and its measured decay properties indicate that states in ${}^{213}$Pb are characterized by the seniority quantum number that counts the nucleons not in pairs coupled to angular momentum $J=0$. The conservation of seniority is a consequence of the Berry phase associated with particle-hole conjugation, which becomes gauge invariant and therefore observable in semi-magic nuclei where nucleons half-fill the valence shell. The $\gamma$-ray spectroscopic observables in ${}^{213}$Pb are thus found to be driven by two mechanisms, particle-hole conjugation and seniority conservation, which are intertwined through the Berry phase.

   nucl-exnucl-thPLB(2021)·13 citations
2. 02*

   Urca Nuclide Production in Type-I X-ray Bursts and Implications for Nuclear Physics Studies

   Grant Merz · Zach Meisel🇺🇸

   The thermal structure of accreting neutron stars is affected by the presence of urca nuclei in the neutron star crust. Nuclear isobars harboring urca nuclides can be produced in the ashes of Type I X-ray bursts, but the details of their production have not yet been explored. Using the code {\tt MESA}, we investigate urca nuclide production in a one-dimensional model of Type I X-ray bursts using astrophysical conditions thought to resemble the source GS 1826-24. We find that high-mass ($A\ge 55$) urca nuclei are primarily produced late in the X-ray burst, during hydrogen-burning freeze-out that corresponds to the tail of the burst light curve. The $\sim 0.4$--0.6~GK temperature relevant for nucleosynthesis of these urca nuclides is much lower than the $\sim 1$~GK temperature most relevant for X-ray burst light curve impacts by nuclear reaction rates involving high-mass nuclides. The latter temperature is often assumed for nuclear physics studies. Therefore, our findings alter the excitation energy range of interest in compound nuclei for nuclear physics studies of urca nuclide production. We demonstrate that for some cases this will need to be considered in planning for nuclear physics experiments. Additionally, we show that the lower temperature range for urca nuclide production explains why variations of some nuclear reaction rates in model calculations impacts the burst light curve but not local features of the burst ashes.

   ↳ astro-ph.HEnucl-exMNRAS(2020)·9 citations
3. 03*

   Nuclear liquid-gas phase transition with machine learning

   Rui Wang🇨🇳 · Yu-Gang Ma🇨🇳 · R. Wada🇺🇸 · Lie-Wen Chen🇨🇳 · Wan-Bing He🇨🇳 · Huan-Ling Liu🇨🇳 · Kai-Jia Sun🇺🇸

   The machine-learning techniques have shown their capability for studying phase transitions in condensed matter physics. Here, we employ the machine-learning techniques to study the nuclear liquid-gas phase transition. We adopt an unsupervised learning and classify the liquid and gas phases of nuclei directly from the final state raw experimental data of heavy-ion reactions. Based on a confusion scheme which combines the supervised and unsupervised learning, we obtain the limiting temperature of the nuclear liquid-gas phase transition. Its value $9.24\pm 0.04\mathrm{MeV}$ is consistent with that obtained by the traditional caloric curve method. Our study explores the paradigm of combining the machine-learning techniques with heavy-ion experimental data, and it is also instructive for studying the phase transition of other uncontrollable systems, like QCD matter.

   ↳ nucl-thnucl-exPRResearch(2020)·58 citations
4. 04*

   Flavoured Neutrinoless Double Beta Decay

   Lukas Graf🇩🇪 · Sudip Jana🇩🇪 · Manfred Lindner🇩🇪 · Werner Rodejohann🇩🇪 · Xun-Jie Xu🇩🇪

   We discuss a mechanism of neutrinoless double beta decay, where neutrinos of different flavours come into play. This is realized by effective flavour-violating scalar interactions. As one consequence, we find that within the normal mass ordering the neutrino effective mass may no longer vanish due to contributions from other flavours. We evaluate the necessary nuclear matrix elements, consider the interference between the standard diagram and the new scalar one, and analyze a UV-complete model that realizes the scalar interaction. Tests of the complete model are possible at colliders and future neutrino experiments. Our scenario represents an alternative mechanism for neutrinoless double beta decay, where nevertheless lepton number violation resides only in Majorana mass terms of light neutrinos.

   ↳ hep-phhep-exnucl-exPRD(2021)·9 citations
5. 05*

   A transverse momentum differential global analysis of Heavy Ion Collisions

   Govert Nijs🇺🇸 · Wilke van der Schee🇨🇭 · Umut Gürsoy🇳🇱 · Raimond Snellings🇳🇱

   The understanding of heavy ion collisions and its quark-gluon plasma formation requires a complicated interplay of rich physics in a wealth of experimental data. In this work we compare for identified particles the transverse momentum dependence of both the yields and the anisotropic flow coefficients for both PbPb and $p$Pb collisions. We do this in a global model fit including a free streaming prehydrodynamic phase with variable velocity $v_{\text{fs}}$, thereby widening the scope of initial conditions. During the hydrodynamic phase we vary three second order transport coefficients. The free streaming velocity has a preference slightly below the speed of light. In this extended model the bulk viscosity is small and even consistent with zero.

   ↳ nucl-thhep-phnucl-exPRL(2021)·208 citations
6. 06*

   Bayesian analysis of heavy ion collisions with the heavy ion computational framework Trajectum

   Govert Nijs🇺🇸 · Wilke van der Schee🇨🇭 · Umut Gürsoy🇳🇱 · Raimond Snellings🇳🇱

   We introduce a model for heavy ion collisions named Trajectum, which includes an expanded initial stage with a variable free streaming velocity $v_{\mathrm{fs}}$ and a hydrodynamic stage with three varying second order transport coefficients. We describe how to obtain a Gaussian Emulator for this 20-parameter model and show results for key observables. This emulator can be used to obtain Bayesian posterior estimates on the parameters, which we test by an elaborate closure test as well as a convergence study. Lastly, we employ the optimal values of the parameters found in [1] to perform a detailed comparison to experimental data from PbPb and $p$Pb collisions. This includes both observables that have been used to obtain these values as well as wider transverse momentum ranges and new observables such as correlations of event-plane angles.

   ↳ nucl-thhep-phnucl-exPRC(2021)·307 citations
7. 07*

   Non-thermal neutrinos created by shock acceleration in successful and failed core-collapse supernova

   Hiroki Nagakura🇺🇸 · Kenta Hotokezaka🇯🇵

   We present a comprehensive study of neutrino shock acceleration in core-collapse supernova (CCSN). The leading players are heavy leptonic neutrinos, ${\nu }_{\mu }$ and ${\nu }_{\tau }$; the former and latter potentially gain the energy up to $\sim 100$ MeV and $\sim 200$ MeV, respectively, through the shock acceleration. Demonstrating the neutrino shock acceleration by Monte Carlo neutrino transport, we make a statement that it commonly occurs in the early post bounce phase ($\lesssim 50$ ms after bounce) for all massive stellar collapse experiencing nuclear bounce and would reoccur in the late phase ($\gtrsim 100$ ms) for failed CCSNe. This opens up a new possibility to detect high energy neutrinos by terrestrial detectors from Galactic CCSNe; hence, we estimate the event counts for Hyper(Super)-Kamiokande, DUNE, and JUNO. We find that the event count with the energy of $\gtrsim 80$ MeV is a few orders of magnitude higher than that of the thermal neutrinos regardless of the detectors, and muon production may also happen in these detectors by ${\nu }_{\mu }$ with the energy of $\gtrsim 100$ MeV. The neutrino signals provide a precious information on deciphering the inner dynamics of CCSN and placing a constraint on the physics of neutrino oscillation; indeed, the detection of the high energy neutrinos through charged current reaction channels will be a smoking gun evidence of neutrino flavor conversion.

   ↳ astro-ph.HEhep-exhep-phnucl-ex+1MNRAS(2021)·17 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.