Wed·Sep 30, 2020Wednesday·September 30, 2020

1. 01*

   A look into mirrors: A measurement of the $\beta$-asymmetry in ${}^{19}$Ne decay and searches for new physics

   Dustin Combs🇺🇸 · Gordon Jones🇺🇸 · William Anderson🇺🇸 · Frank Calaprice🇺🇸 · Leendert Hayen🇺🇸 · Albert Young🇺🇸

   High precision measurements of isospin $T=1/2$ decays in the neutron and nuclei provide strong model-independent constraints on extensions to the standard model of particle physics. A measurement of the $\beta$-asymmetry in ${}^{19}$Ne decay between the initial nuclear spin and the direction of the emitted positron is presented which establishes this decay as the most precisely characterized nuclear mirror and fixes the Fermi-to-Gamow-Teller mixing ratio to $\rho =1.6014(+21/-28{)}_{sys}(8{)}_{stat}$. This is consistent with the previous, most precise measurement, produces a value of the CKM unitarity parameter $V_{ud}$ in agreement with the nuclear mirror, neutron and superallowed $\beta$-decay data sets, shows no evidence for second class currents, and can be effectively used with neutron decay data to place a limits on exotic tensor couplings.

   nucl-ex12 citations
2. 02*

   Precise Half-Life Values for Two-Neutrino Double-$\beta$ Decay: 2020 review

   Alexander Barabash🇷🇺

   All existing positive results on two-neutrino double beta decay and two-neutrino double electron capture in different nuclei have been analyzed. Weighted average and recommended half-life values for ${}^{48}$Ca, ${}^{76}$Ge, ${}^{82}$Se, ${}^{96}$Zr, ${}^{100}$Mo, ${}^{100}$Mo - ${}^{100}$Ru ($0_1^{+}$), ${}^{116}$Cd, ${}^{128}$Te, ${}^{130}$Te, ${}^{136}$Xe, ${}^{150}$Nd, ${}^{150}$Nd - ${}^{150}$Sm ($0_1^{+}$), ${}^{238}$U, ${}^{78}$Kr, ${}^{124}$Xe and ${}^{130}$Ba have been obtained. Given the measured half-life values, effective nuclear matrix elements for all these transitions were calculated.

   nucl-exUniverse(2020)·153 citations
3. 03*

   The ${}^{229}$Th isomer: prospects for a nuclear optical clock

   Lars von der Wense · Benedict Seiferle

   The proposal for the development of a nuclear optical clock has triggered a multitude of experimental and theoretical studies. In particular the prediction of an unprecedented systematic frequency uncertainty of about $10^{-19}$ has rendered a nuclear clock an interesting tool for many applications, potentially even for a re-definition of the second. The focus of the corresponding research is a nuclear transition of the ${}^{229}$Th nucleus, which possesses a uniquely low nuclear excitation energy of only $8.12\pm 0.11$ eV ($152.7\pm 2.1$ nm). This energy is sufficiently low to allow for nuclear laser spectroscopy, an inherent requirement for a nuclear clock. Recently, some significant progress toward the development of a nuclear frequency standard has been made and by today there is no doubt that a nuclear clock will become reality, most likely not even in the too far future. Here we present a comprehensive review of the current status of nuclear clock development with the objective of providing a rather complete list of literature related to the topic, which could serve as a reference for future investigations.

   ↳ physics.atom-phnucl-exEPJA(2020)·38 citations
4. 04*

   Resolving the Bethe-Salpeter kernel

   Si-Xue Qin🇨🇳 · Craig D. Roberts🇨🇳

   A novel method for constructing a Bethe-Salpeter kernel for the meson bound-state problem is described. It produces a closed-form kernel that is symmetry-consistent (discrete and continuous) with the gap equation defined by any admissible gluon-quark vertex. Applicable even when the diagrammatic content of that vertex is unknown, the scheme can foster new synergies between continuum and lattice approaches to strong interactions. The framework is illustrated by demonstrating that the presence of a dressed-quark anomalous magnetic moment in the gluon-quark vertex, an emergent feature of strong interactions, can remedy many defects of widely used meson bound-state kernels, including the level ordering of pseudoscalar and vector meson radial excitations.

   ↳ hep-phhep-exhep-latnucl-ex+1Chin.Phys.Lett.(2021)·51 citations
5. 05*

   Bayesian inference of dense matter EOS encapsulating a first-order hadron-quark phase transition from observables of canonical neutron stars

   Wen-Jie Xie🇨🇳 · Bao-An Li🇺🇸

   [Purpose:] We infer the posterior probability distribution functions (PDFs) and correlations of nine parameters characterizing the EOS of dense neutron-rich matter encapsulating a first-order hadron-quark phase transition from the radius data of canonical NSs reported by LIGO/VIRGO, NICER and Chandra Collaborations. We also infer the quark matter (QM) mass fraction and its radius in a 1.4 M${}_{\odot }$ NS and predict their values in more massive NSs. [Method:] Meta-modelings are used to generate both hadronic and QM EOSs in the Markov-Chain Monte Carlo sampling process within the Bayesian statistical framework. An explicitly isospin-dependent parametric EOS for the $npe\mu$ matter in NSs at $\beta$ equilibrium is connected through the Maxwell construction to the QM EOS described by the constant speed of sound (CSS) model of Alford, Han and Prakash. [Results:] (1) The most probable values of the hadron-quark transition density ${\rho }_t/{\rho }_0$ and the relative energy density jump there $\text{De}\text{ep}/{\text{ep}}_t$ are ${\rho }_t/{\rho }_0=1.6_{-0.4}^{+1.2}$ and $\text{De}\text{ep}/{\text{ep}}_t=0.4_{-0.15}^{+0.20}$ at 68\% confidence level, respectively. The corresponding probability distribution of QM fraction in a 1.4 M${}_{\odot }$ NS peaks around 0.9 in a 10 km sphere. Strongly correlated to the PDFs of ${\rho }_t$ and $\text{De}\text{ep}/{\text{ep}}_t$, the PDF of the QM speed of sound squared $\text{cQMsq}/c^2$ peaks at $0.95_{-0.35}^{+0.05}$, and the total probability of being less than 1/3 is very small. (2) The correlations between PDFs of hadronic and QM EOS parameters are very weak. [Conclusions:] The available astrophysical data considered together with all known EOS constraints from theories and terrestrial nuclear experiments prefer the formation of a large volume of QM even in canonical NSs.

   ↳ nucl-thastro-ph.HEnucl-exPRC(2021)·77 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.