Chinese Physics C

Measurement of ⁸⁵Rb(n, 2n)⁸⁴Rb reaction cross-section from 12 MeV up to 19.8 MeV

Chuanxin Zhu, Jia Wang, Li Jiang, Pu Zheng

Published: , doi: 10.1088/1674-1137/44/3/034001

Abstract:
The cross-section data of the ⁸⁵Rb(n, 2n)⁸⁴Rb reaction have been measured with the neutron energies of 12 MeV to 19.8 MeV using the activation technique and the relative method. The ⁸⁵Rb samples were irradiated on the surface of a two-ring orientation assembly with neutrons produced from the ³H(d, n)⁴He reaction at the 5SDH-2 1.7-MV Tandem accelerator in China. Theoretical model calculations were performed with the TALYS-1.9 code. The present data were compared with previously obtained experimental data and the available evaluated data.

Towards the meV limit of the effective neutrino mass in neutrinoless double-beta decays

Jun Cao, Guo-yuan Huang, Yu-Feng Li, Yifang Wang, Liang-Jian Wen, Zhi-zhong Xing, Zhen-hua Zhao, Shun Zhou

Published: , doi: 10.1088/1674-1137/44/3/033103

Abstract:
We emphasize that it is extremely important for future neutrinoless double-beta ($0\nu\beta\beta$) decay experiments to reach the sensitivity to the effective neutrino mass $|m_{\beta\beta}| \approx 1\;{\rm {meV}}$. With such a sensitivity, it is highly possible to discover the signals of $0\nu\beta\beta$ decays. If no signal is observed at this sensitivity level, then either neutrinos are Dirac particles or stringent constraints can be placed on their Majorana masses. In this paper, assuming the sensitivity of $|m_{\beta\beta}| \approx 1\;{\rm {meV}}$ for future $0\nu\beta\beta$ decay experiments and the precisions on neutrino oscillation parameters after the JUNO experiment, we fully explore the constrained regions of the lightest neutrino mass $m_1$ and two Majorana-type CP-violating phases $\{\rho, \sigma\}$. Several important conclusions in the case of normal neutrino mass ordering can be made. First, the lightest neutrino mass is severely constrained to a narrow range $m_1 \in [0.7, 8]\;{\rm {meV}}$, which together with the precision measurements of neutrino mass-squared differences from oscillation experiments completely determines the neutrino mass spectrum $m_2 \in [8.6, 11.7]\;{\rm {meV}}$ and $m_3 \in [50.3, 50.9]\;{\rm {meV}}$. Second, one of the two Majorana CP-violating phases is limited to $\rho \in [130^\circ, 230^\circ]$, which cannot be obtained from any other realistic experiments. Third, the sum of three neutrino masses is found to be $\Sigma \equiv m_1 + m_2 + m_3 \in [59.2, 72.6]\;{\rm {meV}}$, while the effective neutrino mass for beta decays turns out to be $m_\beta \equiv (|U_{e1}|^2 m^2_1 + |U_{e2}|^2 m^2_2 + |U_{e3}|^2 m^2_3)^{1/2}\in [8.9, 12.6]\;{\rm {meV}}$. These observations clearly set up the roadmap for future non-oscillation neutrino experiments aiming to solve the fundamental problems in neutrino physics.

High-K multi-particle bands and pairing reduction in ²⁵⁴No

Xiao-Tao He, Shu-Yong Zhao, Zhen-Hua Zhang, Zhong-Zhou Ren

Published: , doi: 10.1088/1674-1137/44/3/034106

Abstract:
The multi-particle states and rotational properties of the two-particle bands in $^{254}{\rm{No}}$ are investigated by the cranked shell model with pairing correlations treated by the particle number conserving method. The rotational bands on top of the two-particle $K^{\pi}=3^+, \;8^-$ and $10^+$ states and the pairing reduction are studied theoretically in $^{254}{\rm{No}}$ for the first time. The experimental excitation energies and moments of inertia of the multi-particle states are reproduced well by the calculations. Better agreement with the data is achieved by including the high-order deformation $\varepsilon_{6}$, which leads to enlarged $Z=100$ and $N=152$ deformed shell gaps. An increase of $J^{(1)}$ in these two-particle bands compared with the ground state band is attributed to the pairing reduction due to the Pauli blocking effect.

Drawing insights from pion parton distributions

Minghui Ding, Khépani Raya, Daniele Binosi, Lei Chang, C. D. Roberts, S. M. Schmidt

Published: , doi: 10.1088/1674-1137/44/3/031001

Abstract:
A symmetry-preserving continuum approach to the two valence-body bound-state problem is used to calculate the valence, glue and sea distributions within the pion; unifying them with, inter alia, electromagnetic pion elastic and transition form factors. The analysis reveals the following momentum fractions at the scale $\zeta_2:=2\,{\rm{GeV:}}\langle x_{\rm valence} \rangle = 0.48(3)$, $\langle x_{\rm glue} \rangle = 0.41(2)$, $\langle x_{\rm sea} \rangle = 0.11(2)$; and despite hardening induced by the emergent phenomenon of dynamical chiral symmetry breaking, the valence-quark distribution function, $q^\pi(x)$, exhibits the $x\simeq 1$ behaviour predicted by quantum chromodynamics (QCD). After evolution to $\zeta=5.2\,{\rm{GeV}}$, the prediction for $q^\pi(x)$ matches that obtained using lattice-regularised QCD. This confluence should both stimulate improved analyses of existing data and aid in planning efforts to obtain new data on the pion distribution functions.

Comparative study of the forward and backward methods for calculating jet properties in pp collisions at ${\sqrt{ s}}$=7 TeV

Yu-Liang Yan, Ayut Limphirat, Dai-Mei Zhou, Pornrad Srisawad, Yupeng Yan, Chunbin Yang, Xu Cai, Ben-Hao Sa

Published: , doi: 10.1088/1674-1137/44/3/034104

Abstract:
We propose a forward method based on PYTHIA6.4 to study the jet properties in ultra-relativistic pp collisions. In the forward method, the partonic initial states are first generated with PYTHIA6.4 and then hadronized in the Lund string fragmentation model, and finally the hadronic jets are constructed from the created hadrons. Jet properties calculated with the forward method for pp collisions at $\sqrt{s}$=7 TeV are comparable to those calculated with the usual anti-$k_t$ algorithm (backward method) in PYTHIA6.4. The comparison between the backward and forward methods may contribute to the understanding of the partonic origin of jets in the backward method.

Nuclear chart in covariant density functional theory with dynamic correlations: From oxygen to tin

Yi-Long Yang, Ya-Kun Wang

Published: , doi: 10.1088/1674-1137/44/3/034102

Abstract:
Nuclear masses of even-even nuclei with the proton number $8\leqslant Z\leqslant 50$ (O to Sn isotopes) from the proton drip line to neutron drip line are investigated using the triaxial relativistic Hartree-Bogoliubov theory with the relativistic density functional PC-PK1. Further, the dynamical correlation energies (DCEs) associated with the rotational motion and quadrupole-shaped vibrational motion are taken into account by the five-dimensional collective Hamiltonian (5DCH) method. The root-mean-square deviation with respect to the experimental masses reduces from 2.50 to 1.59 MeV after the consideration of DCEs. The inclusion of DCEs has little influence on the position of drip lines, and the predicted numbers of bound even-even nuclei between proton and neutron drip lines from O to Sn isotopes are 569 and 564 with and without DCEs, respectively.

Charged pion condensation in anti-parallel electromagnetic fields and nonzero isospin density

Jingyi Chao, Mei Huang, Andrey Radzhabov

Published: , doi: 10.1088/1674-1137/44/3/034105

Abstract:
The formation of charged pion condensate in anti-parallel electromagnetic fields and in the presence of the isospin chemical potential is studied in the two-flavor Nambu–Jona-Lasinio model. The method of Schwinger proper time is extended to explore the quantities in the off-diagonal flavor space, i.e. the charged pion. In this framework, $\pi^{\pm}$ are treated as bound states of quarks and not as point-like charged particles. The isospin chemical potential plays the role of a trigger for charged pion condensation. We obtain the associated effective potential as a function of the strength of the electromagnetic fields and find that it contains a sextic term which possibly induces a weak first order phase transition. The dependence of pion condensation on model parameters is investigated.

Neutron-antineutron oscillations in the deuteron studied with NN and ${{\bar NN}}$ interactions based on chiral effective field theory

Johann Haidenbauer, Ulf-G. Meißner

Published: , doi: 10.1088/1674-1137/44/3/033101

Abstract:
Neutron-antineutron ($ n-\bar n $) oscillations in the deuteron are considered. Specifically, the deuteron lifetime is calculated in terms of the free-space $ n-\bar n $ oscillation time $ \tau_{n-\bar n} $ based on $ NN $ and $ \bar NN $ interactions derived within chiral effective field theory (EFT). This results in $ (2.6\pm 0.1) \times 10^{22}\,\tau^2_{n-\bar n} $ s, which is close to the value obtained by Dover and collaborators more than three decades ago, but disagrees with recent EFT calculations that were performed within the perturbative scheme proposed by Kaplan, Savage, and Wise. Possible reasons for the difference are discussed.

Applicability of ⁹Be global optical potential to description of ^8,10,11B elastic scattering

Yong-Li Xu, Yin-Lu Han, Hai-Ying Liang, Zhen-Dong Wu, Hai-Rui Guo, Chong-Hai Cai

Published: , doi: 10.1088/1674-1137/44/3/034101

Abstract:
We achieved a set of ⁹Be global phenomenological optical model potentials by fitting a large experimental dataset of the elastic scattering observable for target mass numbers from 24 to 209. The obtained ⁹Be global optical model potential was applied to predict elastic-scattering angular distributions and total reaction cross-sections of ^8,10,11B projectiles. The predictions are made by performing a detailed analysis comparing with the available experimental data. Furthermore, these elastic scattering observables are also predicted for some lighter targets outside of the given mass number range, and reasonable results are obtained. Possible physical explanations for the observed differences are also discussed.

In Press