Nuclear Theory·nucl-th

Thursday·January 27, 2022

6 papers—5 primary·1 cross-listed

01
[Submitted on 25 Jan 2022]
Nucleon-Nucleon Short-Ranged Correlations, $β$ Decay and the Unitarity of the CKM Matrix
Levi Condren🇺🇸 · Gerald A. Miller🇺🇸
The influence of nucleon-nucleon short-ranged correlations (SRC) on nuclear super-allowed $β$ decay is examined. The need for this is driven by the observed depletion of spectroscopic strength obtained in studies of $(e, e^{'})$ and $(d,^{3} He)$ reactions on a wide variety of nuclei. We show that the influence of SRC is model-dependent, but may be very substantial. The $^{46}$ V nucleus is used as an example. The resulting impact on studies of the unitarity of the Cabibbo-Kobayashi-Maskawa (CKM) matrix element is discussed.
Comments:
7 pages, 0 figures. Several improvements in this version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2201.10651 [pdf]
PRC(2022)·14 citations
02
[Submitted on 26 Jan 2022]
OMR-NPA: Optimized Matrix Representation of Nucleon Pair Approximation
Y. Lei · Y. Lu
We optimize the matrix representation of the nucleon-pair approximation (NPA) of the nuclear shell model. The NPA is a widely adopted truncation approach of the nuclear shell model and proves to be effective in describing low-lying states of medium-heavy and heavy nuclei. Due to simplified (yet flexible) commutators and absolute elimination of angular momentum coupling, the matrix representation provides a formalism for the $M$ -scheme NPA more efficient than others as far as we know. It also enables the practicable organization and storage design for intermediate results, including generated collective pairs, matrix products, and matrix traces, so that further optimization is achieved by reducing repetitive matrix operations, which are the most time-consuming procedures in the matrix-represented $M$ -scheme NPA. We also describe optimizations specified for the $M$ -scheme NPA, realized by invoking the Wigner-Eckart theorem, time-reversal symmetry, and conjugate operation of spherical tensors. Our optimization makes the combination of matrix representation and NPA more profitable. Such an implementation denoted by optimized matrix representation of NPA (OMR-NPA) is publicly released with open source. Its performance is analyzed and compared against unoptimized NPA codes.
Comments:
9 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2201.10721 [pdf]
1 citation
03
[Submitted on 26 Jan 2022]
Impact of nuclear structure on the CME background in $_{44}^{96}$ Ru + $_{44}^{96}$ Ru and $_{40}^{96}$ Zr + $_{40}^{96}$ Zr collisions at $s_{N N}$ = 7.7 $\sim$ 200 GeV from a multiphase transport model
Fei Li🇨🇳 · Yu-Gang Ma🇨🇳 · Song Zhang🇨🇳 · Guo-Liang Ma🇨🇳 · Qi-Ye Shou🇨🇳
Impacts of nuclear structure on multiplicity ( $N_{c h}$ ) and anisotropic flows ( $v_{2}$ and $v_{3}$ ) in the isobaric collisions of $_{44}^{96}$ Ru + $_{44}^{96}$ Ru and $_{40}^{96}$ Zr + $_{40}^{96}$ Zr at $s_{N N}$ = 7.7, 27, 62.4 and 200 GeV are investigated by using the string melting version of A MultiPhase Transport (AMPT) model. In comparison with the experimental data released recently by the STAR collaboration, it is found that the impact of quadrupole deformation $β_{2}$ on the $v_{2}$ difference is mainly manifested in the most central collisions, while the octupole deformation $β_{3}$ is in the near-central collisions, and the neutron skin effect dominates in the mid-central collisions. Viewing from the energy dependence, these effects are magnified at lower energies.
Comments:
10 pages, 7 figures, 1 table
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2201.10994 [pdf]
PRC(2022)·17 citations
04
[Submitted on 26 Jan 2022]
Breakup effects in the $^{16} C + p$ and $^{16} C + d$ reactions
Shubhchintak · P. Descouvemont
We analyze the $^{16} C + p$ and $^{16} C + d$ reactions within the four- and five-body Continuum Discretized Coupled Channel (CDCC) method. The $^{16}$ C nucleus is described by a $^{14} C + n + n$ configuration in hyperspherical coordinates. This description reproduces fairly well several $^{16}$ C low-lying states. First we analyze the $2^{+} \to 0^{+}$ $E 2$ transition amplitude, which confirms that an effective charge must be introduced to reproduce the experimental value. Then, proton and deuteron elastic and inelastic scattering are investigated by including $^{16}$ C pseudostates, which simulate the $^{14} C + n + n$ continuum. In $^{16} C + d$ , the deuteron breakup is taken into account with $p + n$ two-body pseudostates. A fair agreement with experiment is obtained without any fitting parameter. Breakup effects are in general small, but improve the agreement with experiment.
Comments:
Accepted for publication in Physical Review C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2201.11012 [pdf]
PRC(2022)·5 citations
05
[Submitted on 26 Jan 2022]
The heavy ions are "preheated" prior to hight energy collisions
Edward Shuryak🇺🇸
The so called "isobar run" or RHIC was designed to compare a number of observables for collisions of $_{40}^{96} Z r$ with those of $_{44}^{96} R u$ , aimed at identification of $Z$ -dependent effects. However, as the STAR data have shown with unprecedented accuracy, these two nuclides differ stronger than expected, producing effects larger than those depending on charge. So far, multiple studies tried to quantify their shape differences, in relation to various observables. General consensus is that these differences somehow should be related to nuclear structure, in particularly properties of the lowest excited states. Yet the precise connection between these fields -- low and high energy nuclear physics -- is still missing. In this paper I propose such a connection, via a concept of thermal density matrices of a "preheated" nuclei. The effective temperature should parameterize which set of excited states should be included in the calculations. I also suggest semiclassical "flucton" method at finite temperatures to be used to calculate thermal density matrices.
Comments:
v2 has references added and some editing of the original text
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2201.11064 [pdf]
1 citation
06
[Submitted on 26 Jan 2022] (cross-list from hep-ph)
Analysis of the $γ n \to K^{+} Σ^{-} (1385)$ photoproduction
Ai-Chao Wang🇨🇳 · Neng-Chang Wei🇨🇳 · Fei Huang🇨🇳
In our previous work [Phys. Rev. D $101$ , 074025 (2020)], the photoproduction $γ p \to K^{+} Σ^{0} (1385)$ has been investigated within an effective Lagrangian approach. There, the reaction amplitudes were constructed by considering the $t$ -channel $K$ and $K^{*} (892)$ exchanges, $s$ -channel $N$ contribution, $u$ -channel $Λ$ exchange, generalized contact term, and a minimum number of $s$ -channel $N$ and $Δ$ resonance diagrams. It was found that the inclusion of one of the $N (1895) 1/2^{-}$ , $Δ (1900) 1/2^{-}$ , and $Δ (1930) 5/2^{-}$ resonances is essential to reproduce the available differential and total cross-section data for $γ p \to K^{+} Σ^{0} (1385)$ . In the present work, we employ the same model to study the photoproduction $γ n \to K^{+} Σ^{-} (1385)$ , with the purpose being to understand the reaction mechanism and, in particular, to figure out which one of the $N (1895) 1/2^{-}$ , $Δ (1900) 1/2^{-}$ , and $Δ (1930) 5/2^{-}$ resonances is really capable for a simultaneous description of the data for both $K^{+} Σ^{0} (1385)$ and $K^{+} Σ^{-} (1385)$ photoproduction reactions. The results show that the available data on differential and total cross sections and photo-beam asymmetries for $γ n \to K^{+} Σ^{-} (1385)$ can be reproduced only with the inclusion of the $Δ (1930) 5/2^{-}$ resonance rather than the other two. The generalized contact term and the $t$ -channel $K$ exchange are found to dominate the background contributions. The resonance $Δ (1930) 5/2^{-}$ provides the most important contributions in the whole energy region considered, and it is responsible for the bump structure exhibited in the total cross sections.
Comments:
7 pages, 7 figures. Accepted for publication in PRD
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2201.10778 [pdf]
PRD(2022)·7 citations

Affiliations

first authorsco-authorsvia INSPIRE

Nucleon-Nucleon Short-Ranged Correlations, β Decay and the Unitarity of the CKM Matrix

OMR-NPA: Optimized Matrix Representation of Nucleon Pair Approximation

Impact of nuclear structure on the CME background in 4496​Ru + 4496​Ru and 4096​Zr + 4096​Zr collisions at sNN​​ = 7.7 ∼ 200 GeV from a multiphase transport model

Breakup effects in the 16C+p and 16C+d reactions

The heavy ions are "preheated" prior to hight energy collisions

Analysis of the γn→K+Σ−(1385) photoproduction

Affiliations

Nucleon-Nucleon Short-Ranged Correlations, $β$ Decay and the Unitarity of the CKM Matrix

Impact of nuclear structure on the CME background in $_{44}^{96}$ Ru + $_{44}^{96}$ Ru and $_{40}^{96}$ Zr + $_{40}^{96}$ Zr collisions at $s_{N N}$ = 7.7 $\sim$ 200 GeV from a multiphase transport model

Breakup effects in the $^{16} C + p$ and $^{16} C + d$ reactions

Analysis of the $γ n \to K^{+} Σ^{-} (1385)$ photoproduction