Highlights
• The NUBASE2020 evaluation of nuclear physics properties
2021, 45(3): 030001. doi: 10.1088/1674-1137/abddae
The NUBASE2020 evaluation contains the recommended values of the main nuclear physics properties for all nuclei in their ground and excited, isomeric (T1/2 $\ge$ 100 ns) states. It encompasses all experimental data published in primary (journal articles) and secondary (mainly laboratory reports and conference proceedings) references, together with the corresponding bibliographical information. In cases where no experimental data were available for a particular nuclide, trends in the behavior of specific properties in neighboring nuclei were examined and estimated values are proposed. Evaluation procedures and policies that were used during the development of this evaluated nuclear data library are presented, together with a detailed table of recommended values and their uncertainties.
• The AME 2020 atomic mass evaluation (II). Tables, graphs and references
2021, 45(3): 030003. doi: 10.1088/1674-1137/abddaf
This is the second part of the new evaluation of atomic masses, AME2020. Using least-squares adjustments to all evaluated and accepted experimental data, described in Part I, we derived tables with numerical values and graphs which supersede those given in AME2016. The first table presents the recommended atomic mass values and their uncertainties. It is followed by a table of the influences of data on primary nuclides, a table of various reaction and decay energies, and finally, a series of graphs of separation and decay energies. The last section of this paper provides all input data references that were used in the AME2020 and the NUBASE2020 evaluations.
• The AME 2020 atomic mass evaluation (I). Evaluation of input data, and adjustment procedures
2021, 45(3): 030002. doi: 10.1088/1674-1137/abddb0
This is the first of two articles (Part I and Part II) that presents the results of the new atomic mass evaluation, AME2020. It includes complete information on the experimental input data that were used to derive the tables of recommended values which are given in Part II. This article describes the evaluation philosophy and procedures that were implemented in the selection of specific nuclear reaction, decay and mass-spectrometric data which were used in a least-squares fit adjustment in order to determine the recommended mass values and their uncertainties. All input data, including both the accepted and rejected ones, are tabulated and compared with the adjusted values obtained from the least-squares fit analysis. Differences with the previous AME2016 evaluation are discussed and specific examples are presented for several nuclides that may be of interest to AME users.
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• Feasibility study of CP violation in ${{{\mathit{\boldsymbol{\tau^-}}}} {\mathit{\boldsymbol{\rightarrow K_{S}}}\pi^{-} \nu_{\tau}}}$ decays at the Super Tau Charm Facility
Published: 2021-04-10, doi: 10.1088/1674-1137/abeb07
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We report a feasibility study for violation in $\tau^{-}\rightarrow K_{S}\pi^{-} \nu_{\tau}$ decays at a Super Tau Charm Facility (STCF). With an expected luminosity of 1 ab$^{-1}$ collected by STCF per year at a center-of-mass energy of 4.26 GeV, the statistical sensitivity for CP violation is determined to be of order $9.7\times10^{-4}$ by measuring the decay-rate difference between $\tau^{+}\rightarrow K_{S}\pi^{+}\bar{\nu}_{\tau}$ and $\tau^{-}\rightarrow K_{S}\pi^{-} \nu_{\tau}$. The analysis is performed using a reliable fast simulation software package, which can describe the detector responses properly and vary the responses flexibly for further optimization. Moreover, the energy-dependent efficiencies for reconstructing $\tau^{-}\rightarrow K_{S}\pi^{-} \nu_{\tau}$ are presented. The expected CP sensitivity is proportional to $1/\sqrt{\cal{L}}$ in the energy region from 4.0 to 5.0 GeV. The sensitivity of CP violation is of order $3.1\times10^{-4}$ with 10 ab$^{-1}$ integrated luminosity, which is equivalent to ten years' data taking in this energy region at STCF.
• Nucleon-pair approximation with uncoupled representation
Published: 2021-04-10, doi: 10.1088/1674-1137/abe3ed
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In this paper, we propose an approach to nucleon-pair approximation (NPA) with an m-scheme bases, in which the collective nucleon pairs are represented in terms of antisymmetric matrices, and commutations between nucleon pairs are given using a matrix multiplication that avoids angular-momentum couplings and recouplings. Therefore the present approach significantly simplifies the NPA computation. Furthermore, it is formulated on the same footing with and without isospin.
• Sound velocity in dense stellar matter with strangeness and compact stars
Published: 2021-04-10, doi: 10.1088/1674-1137/abea0d
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The phase state of dense matter in the intermediate density range ($\sim$1-10 times the nuclear saturation density) is both intriguing and unclear and can have important observable effects in the present gravitational wave era of neutron stars. As matter density increases in compact stars, the sound velocity is expected to approach the conformal limit ($c_s/c=1/\sqrt{3}$) at high densities and should also fulfill the causality limit ($c_s/c<1$). However, its detailed behavior remains a prominent topic of debate. It was suggested that the sound velocity of dense matter could be an important indicator of a deconfinement phase transition, where a particular shape might be expected for its density dependence. In this work, we explore the general properties of the sound velocity and the adiabatic index of dense matter in hybrid stars as well as in neutron stars and quark stars. Various conditions are employed for the hadron-quark phase transition with varying interface tension. We find that the expected behavior of the sound velocity can also be achieved by the nonperturbative properties of the quark phase, in addition to a deconfinement phase transition. Moreover, it leads to a more compact star with a similar mass. We then propose a new class of quark star equation of states, which can be tested by future high-precision radius measurements of pulsar-like objects.
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2021 Vol. 45, No. 4
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