## 2021 Vol. 45, No. 6

Display Method: |

2021, 45(6): 062001. doi: 10.1088/1674-1137/abf138

**Abstract:**

The Back-n white neutron source (known as Back-n) is based on back-streaming neutrons from the spallation target at the China Spallation Neutron Source (CSNS). With its excellent beam properties, e.g., a neutron flux of approximately 1.8×10

^{7}n/cm

^{2}/s at 55 m from the spallation target, energy range spanning from 0.5 eV to 200 MeV, and time-of-flight resolution of a few per thousand, along with the equipped physical spectrometers, Back-n is considered to be among the best facilities in the world for carrying out nuclear data measurements. Since its completion and commencement of operation in May 2018, five types of cross-section measurements concerning neutron capture cross-sections, fission cross-sections, total cross-sections, light charged particle emissions, in-beam gamma spectra, and more than forty nuclides have been measured. This article presents an overview of the experimental setup and result analysis on the neutron-induced cross-section measurements and gamma spectroscopy at Back-n in the initial years.

2021, 45(6): 063101. doi: 10.1088/1674-1137/abeda6

**Abstract:**

The long-standing Galactic center gamma-ray excess could be explained by GeV dark matter (DM) annihilation, but the DM interpretation seems to conflict with recent joint limits from different astronomical scale observations such as dwarf spheroidal galaxies, the Milky Way halo, and galaxy groups/clusters. Motivated by

^{8}Be and

^{4}He anomalous transitions with possible new interactions mediated by a vector boson

*X*, we consider a small fraction of DM mainly annihilating into a pair of on-shell vector bosons

2021, 45(6): 063102. doi: 10.1088/1674-1137/abeda8

**Abstract:**

Inspired by the newly observed

2021, 45(6): 063103. doi: 10.1088/1674-1137/abf139

**Abstract:**

In this study, the non-trival effect of the selection of reference particles for decay angle definitions is demonstrated when constructing the partial-wave amplitude of multi-body decays using helicity formalism. This issue is often ignored in the standard use case of helicity formalism. A new technique is proposed to test the selection of the particle ordering, and it can also be used as a generalized method to calculate the rotation operators that are used for the final-state alignment between different decay chains. Moreover, numerical validations are performed to support the arguments and to verify the effectiveness of the proposed technique.

2021, 45(6): 063104. doi: 10.1088/1674-1137/abf13b

**Abstract:**

In this article, we illustrate how to calculate the hadronic coupling constants of the pentaquark states with QCD sum rules based on rigorous quark-hadron quality. We then study the hadronic coupling constants of the lowest diquark-diquark-antiquark type hidden-charm pentaquark state with spin-parity

2021, 45(6): 063105. doi: 10.1088/1674-1137/abf1de

**Abstract:**

In this article, we consider the ratio of structure functions for heavy quark pair production at low values of

2021, 45(6): 063106. doi: 10.1088/1674-1137/abf488

**Abstract:**

This paper presents perturbative QCD predictions of the electron charge asymmetry for inclusive

*pp*) collisions. Perturbative QCD calculations are performed at next-to-next-to-leading order (NNLO) accuracy using different parton distribution function (PDF) models at 8, 13, and 14 TeV center-of-mass energies of CERN LHC

*pp*collisions. NNLO calculations are performed for electrons with transverse momenta above 20 GeV in the forward electron pseudorapidity region

2021, 45(6): 063107. doi: 10.1088/1674-1137/abf489

**Abstract:**

Anomalies in decays induced by

*D*decays induced by

*D*decays agree with the standard model (SM) predictions, and such agreements can be used to constrain the new physics (NP) contributions. In this work, we extend SM by assuming general effective Hamiltonians describing the

2021, 45(6): 063108. doi: 10.1088/1674-1137/abf4f4

**Abstract:**

The present study is dedicated to light-strange

*S*= −1 and isospin

*I*= 0,

*S*= −1 and

*I*= 1, and

*S*= −2 and

*S*-5

*S*, 1

*P*-4

*P*, 1

*D*-3

*D*, 1

*F*-2

*F*, and 1

*G*(in a few cases) along with all possible spin-parity assignments. Regge trajectories have been explored for the linearity of the calculated masses for

2021, 45(6): 064001. doi: 10.1088/1674-1137/abf136

**Abstract:**

The angle-differential cross sections of neutron-induced deuteron production from carbon were measured at six neutron energies from 25 to 52 MeV relative to those of

*n*-

*p*elastic scattering at the China Spallation Neutron Source (CSNS) Back-n white neutron source. By employing the

*Δ*

*E*-

*E*telescopes of the Light-charged Particle Detector Array (LPDA) system at 15.1° to 55.0° in the laboratory system, ratios of the angle-differential cross sections of the

^{12}C(

*n*,

*xd*) reactions to those of the

*n*-

*p*scattering were measured, and then, the angle-differential cross sections of the

^{12}C(

*n*,

*xd*) reactions were obtained using the angle-differential cross sections of the

*n*-

*p*elastic scattering from the JENDL-4.0/HE-2015 library as the standard. The obtained results are compared with data from previous measurements, all of which are based on mono-energic neutrons, the evaluated data from the JENDL-4.0/ HE-2015 library and the ENDF-B/VIII.0 library, and those from theoretical calculations based on INCA code and Talys-1.9 code. Being the first white-neutron-source-based systematic measurement of the angle-differential cross sections of neutron-induced deuteron production reactions on carbon in several tens of MeV, the present work can provide a reference to the data library considering the lack of experimental data.

2021, 45(6): 064002. doi: 10.1088/1674-1137/abf137

**Abstract:**

The formation of large size clusters, and/or their relative motion as a possible excitation mode, are suggested to be closely related to the origin of deformation in specific cases, namely the case of two doubly-magic clusters or two clusters with nearby characterization. New lifetime data in

*N*=

*Z*

^{76}Sr and

^{80}Zr leading to large

*B*(

*E*2) values are reproduced consistently and well within this approach, along with data for a few neighboring

*N*

*Z*nuclei. These results are compared to previous studies of

^{32}S and

^{20}Ne and all of them support the ideas of the large-scale cluster approach.

2021, 45(6): 064003. doi: 10.1088/1674-1137/abf427

**Abstract:**

We studied the effects of centrality fluctuation and deuteron formation on the cumulant (

_{T}< 2 GeV/

*c*. We compared the results obtained by the centrality bin width correction (CBWC) using charged reference particle multiplicities with the CBWC using impact parameter bins. It was found that, at low energies, the centrality resolution for determining the collision centrality using charged particle multiplicities is not sufficient to reduce the initial volume fluctuation effect for higher-order cumulant analysis. New methods need to be developed to classify events with high centrality resolution for heavy-ion collisions at low energies. Finally, we observed that the formation of deuterons suppresses the higher-order cumulants and correlation functions of protons and found it to be similar to the efficiency effect. This work can serve as a noncritical baseline for the QCD critical point search in the high baryon density region.

2021, 45(6): 064101. doi: 10.1088/1674-1137/abeda7

**Abstract:**

First-principle calculations within the density functional theory framework are used to study the probability of electron capture for the

^{7}Be nucleus. For this purpose, electron density at the

^{7}Be nucleus is computed in Al, Au, Pd, Pt, and Pb environments. Our results show that the half-life of

^{7}Be is changed by implanting

^{7}Be in host environments. Electron affinity of the media and confinement effects are responsible for the change in the half-life of

^{7}Be nucleus. Moreover, electric potential at the

^{7}Be nucleus is calculated. Results show that variations in electric potential are usually consistent with those in electron density at the

^{7}Be nucleus.

2021, 45(6): 064102. doi: 10.1088/1674-1137/abefc3

**Abstract:**

The self-consistent mean field approximation of the two-flavor NJL model, with a free parameter

*T*, and especially to study the location of the QCD critical point. Our results show that in order to match the corresponding lattice results of isospin density and energy density, the contributions of the "exchange" channel need to be considered in the framework of the NJL model, and a weighting factor

2021, 45(6): 064103. doi: 10.1088/1674-1137/abf036

**Abstract:**

The tensor-force effects on the evolution of spin-orbit splittings in neutron drops are investigated within the framework of the relativistic Hartree-Fock theory. For a fair comparison on the pure mean-field level, the results of the relativistic Brueckner-Hartree-Fock calculation with the Bonn A interaction are adopted as meta-data. Through a quantitative analysis, we certify that the

*renormalization persistency*of the tensor force within the framework of density functional theory. This will serve as important guidance for further development of relativistic effective interactions with particular focus on the tensor force.

2021, 45(6): 064104. doi: 10.1088/1674-1137/abf428

**Abstract:**

From a Bayesian analysis of the electric dipole polarizability, the constrained energy of isovector giant dipole resonance, the peak energy of isocalar giant quadrupole resonance, and the constrained energy of isocalar giant monopole resonance in

^{208}Pb, we extract the isoscalar and isovector effective masses in nuclear matter at saturation density

2021, 45(6): 064105. doi: 10.1088/1674-1137/abf4f5

**Abstract:**

Angular correlations between a heavy quark (HQ) and its tagged jet are potentially new tools to gain insight into the in-medium partonic interactions in relativistic heavy-ion collisions. In this work, we present the first theoretical study on the radial profiles of

*B*mesons in jets in Pb+Pb collisions at the Large Hadron Collider (LHC). The initial production of a bottom quark tagged jet in

*p+p*is computed by SHERPA, which matches the next-to-leading order matrix elements with contributions of parton showers, whereas the massive quark traversing the quark-gluon plasma is described by a Monte Carlo model, SHELL, which can simultaneously simulate light and heavy flavor in-medium energy loss within the framework of Langevin evolution. In

*p+p*collisions, we find that at lower

*B*meson radial profiles in jets at

*D*mesons: the jet quenching effects narrow the jet radial profiles of

*B*mesons in jets while broadening those of

*D*mesons in jets. We find that in

*A+A*collisions, the contribution dissipated from the higher

*b*quarks in jets benefit more from the former and suffer less diffusion effect compared to that of

*c*quarks in jets. These findings can be tested in the future experimental measurements at the LHC to gain better understanding of the mass effect of jet quenching.

2021, 45(6): 065101. doi: 10.1088/1674-1137/abefca

**Abstract:**

In this paper, we explore the properties of holographic entanglement entropy (HEE), mutual information (MI) and entanglement of purification (EoP) in holographic Lifshitz theory. These informational quantities exhibit some universal properties of holographic dual field theory. For most configuration parameters and temperatures, these informational quantities change monotonically with the Lifshitz dynamical critical exponent

*z*. However, we also observe some non-monotonic behaviors for these informational quantities in some specific spaces of configuration parameters and temperatures. A particularly interesting phenomenon is that a dome-shaped diagram emerges in the behavior of MI vs

*z*, and correspondingly a trapezoid-shaped profile appears in that of EoP vs

*z*. This means that for some specific configuration parameters and temperatures, the system measured in terms of MI and EoP is entangled only in a certain intermediate range of

*z*.

2021, 45(6): 065102. doi: 10.1088/1674-1137/abf13a

**Abstract:**

Cosmic-ray (CR) anti-nuclei are often considered important observables for indirect dark matter (DM) detection at low kinetic energies, below GeV per nucleon. Since the primary CR fluxes drop quickly towards high energies, the secondary anti-nuclei in CR are expected to be significantly suppressed in high energy regions (

2021, 45(6): 065103. doi: 10.1088/1674-1137/abf1dc

**Abstract:**

Super-entropic black holes possess finite-area but noncompact event horizons and violate the reverse isoperimetric inequality. It has been conjectured that such black holes always have negative specific heat at constant volume

2021, 45(6): 065104. doi: 10.1088/1674-1137/abf48a

**Abstract:**

In this work, we explore the potentiality of future gravitational wave (GW) and Type Ia supernovae (SNe Ia) measurements to detect cosmic opacity by comparing the opacity-free luminosity distance (LD) of GW events with the opacity-dependent LD of SNe Ia observations. The GW data are simulated from the future measurements of the ground-based Einstein Telescope (ET) and the space-borne Deci-Herz Interferometer Gravitational wave Observatory (DECIGO). The SNe Ia data are simulated from the observations of the Wide Field Infrared Survey Telescope (WFIRST) that will be collected over the next few decades. A binning method is adopted to match the GW data with the SNe Ia data at the same redshift

*z*with a selection criterion

2021, 45(6): 065105. doi: 10.1088/1674-1137/abf4f6

**Abstract:**

We studied the pair production of charged scalar particles of a five-dimensional near extremal Reissner-Nordström-Anti de Sitter (RN-AdS

_{5}) black hole. The pair production rate and the absorption cross section ratio in full spacetime are obtained and are shown to have a concise relation with their counterparts in the near horizon region. In addition, the holographic descriptions of the pair production, both in the IR CFT in the near horizon region and the UV CFT at the asymptotic spatial boundary of the RN-AdS

_{5}black hole, are analyzed in the AdS

_{2}/CFT

_{1}and AdS

_{5}/CFT

_{4}correspondences, respectively. This work gives a complete description of scalar pair production in a near extremal RN-AdS

_{5}black hole.

**ISSN** 1674-1137 **CN** 11-5641/O4

Original research articles, Ietters and reviews Covering theory and experiments in the fieids of

- Particle physics
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- Cosmology

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