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Tensor force effect on the exotic structure of neutron-rich Ca isotopes
Yan-Zhao Wang, Xue-Dou Su, Chong Qi, Jian-Zhong Gu
Published: , doi: 10.1088/1674-1137/43/11/114101
The structure of neutron-rich Ca isotopes is studied in the spherical Skyrme-Hartree-Fock-Bogoliubov (SHFB) approach with SLy5, SLy5+T, and 36 sets of TIJ parametrizations. The calculated results are compared with the available experimental data for the average binding energies, two-neutron separation energies and charge radii. It is found that the SLy5+T, T31, and T32 parametrizations reproduce best the experimental properties, especially the neutron shell effects at N = 20, 28 and 32, and the recently measured two-neutron separation energy of 56Ca. The calculations with the SLy5+T and T31 parametrizations are extended to isotopes near the neutron drip line. The neutron giant halo structure in the very neutron-rich Ca isotopes is not seen with these two interactions. However, depleted neutron central densities are found in these nuclei. By analyzing the neutron mean-potential, the reason for the bubble-like structure formation is given.
Searching for neutrino-less nouble neta necay of 136Xe with PandaX-II liquid xenon detector
Kaixiang Ni, Yihui Lai, Abdusalam Abdukerim, Wei Chen, Xun Chen, Yunhua Chen, Xiangyi Cui, Yingjie Fan, Deqing Fang, Changbo Fu, Lisheng Geng, Karl Giboni, Franco Giuliani, Linhui Gu, Xuyuan Guo, Ke Han, Changda He, Di Huang, Yan Huang, Yanlin Huang, Zhou Huang, Peng Ji, Xiangdong Ji, Yonglin Ju, Kun Liang, Huaxuan Liu, Jianglai Liu, Wenbo Ma, Yugang Ma, Yajun Mao, Yue Meng, Parinya Namwongsa, Jinhua Ning, Xuyang Ning, Xiangxiang Ren, Changsong Shang, Lin Si, Andi Tan, Anqing Wang, Hongwei Wang, Meng Wang, Qiuhong Wang, Siguang Wang, Xiuli Wang, Zhou Wang, Mengmeng Wu, Shiyong Wu, Jingkai Xia, Mengjiao Xiao, Pengwei Xie, Binbin Yan, Jijun Yang, Yong Yang, Chunxu Yu, Jumin Yuan, Dan Zhang, Hongguang Zhang, Tao Zhang, Li Zhao, Qibin Zheng, Jifang Zhou, Ning Zhou, Xiaopeng Zhou
Published: , doi: 10.1088/1674-1137/43/11/113001
We report the Neutrino-less Double Beta Decay (NLDBD) search results from PandaX-II dual-phase liquid xenon time projection chamber. The total live time used in this analysis is 403.1 days from June 2016 to August 2018. With NLDBD-optimized event selection criteria, we obtain a fiducial mass of 219 kg of natural xenon. The accumulated xenon exposure is 242 kg·yr, or equivalently 22.2 kg·yr of 136Xe exposure. At the region around 136Xe decay Q-value of 2458 keV, the energy resolution of PandaX-II is 4.2%. We find no evidence of NLDBD in PandaX-II and establish a lower limit for decay half-life of 2.1 $ \times 10^{23} $ yr at the 90% confidence level, which corresponds to an effective Majorana neutrino mass $m_{\beta \beta} < (1.4 - 3.7)$ eV. This is the first NLDBD result reported from a dual-phase xenon experiment.
The contribution of the first forbidden transitions to the nuclear β-decay half-life
Ji-Lin You, Xiao-Ping Zhang, Qi-Jun Zhi, Zhong-Zhou Ren, Qing-Dong Wu
Published: , doi: 10.1088/1674-1137/43/11/114014
$ \beta $-decay half-life is a key quantity for nuclear structure and nucleosynthesis studies. There exist large uncertainties in the contributions of allowed and forbidden transitions to the total $ \beta $-decay life, which limits the resolution of the predicted $ \beta $-decay half-life. We systematically study the contribution of the first forbidden (FF) transitions to the $ \beta^{-} $-decay half-life, and quantify it with a formula based on simple physics considerations. We also propose a new formula for calculation of the $ \beta^{-} $-decay half-life that includes the FF contribution. It is shown that the inclusion of the contribution of FF transitions significantly improves the precision of calculations of the $ \beta^{-} $-decay half-life. By fitting of the RQRPA results for neutron-rich $ Z = 47 $, 57 isotopes and $ N = 80 $, 94 isotones, the formula for the contribution of the FF transitions gives similar results as the RQRPA calculations. However, because of limited experimental data for the branching ratios of unstable nuclei, the fit parameters are not fully constrained. Therefore, the proposed formula for the $ \beta^{-} $-decay half-life is more suitable for calculations of half-lives than of the FF contributions. The formula could be used to predict the $ \beta^{-} $-decay half-life in nuclear structure studies as well as nucleosynthesis calculations in stars.
Giant dipole resonance parameters from photoabsorption cross-sections
Yuan Tian, Xi Tao, Jimin Wang, Xianbo Ke, Ruirui Xu, Zhigang Ge
Published: , doi: 10.1088/1674-1137/43/11/114102
The structural effect is believed to have no influence on the decay properties of medium and heavy-mass nuclei at excitation energies above the pairing gap. These properties can be described by statistical properties using so-called photon strength functions for different multipolarities, and directly related to the photoabsorption cross-section ($\sigma_{\rm abs}$). $\sigma_{\rm abs}$ is dominated by the electric giant dipole resonance at $\gamma$ energy $\epsilon_\gamma \leqslant 40$ MeV. In this study, we construct two kinds of systematic giant dipole resonance parameters by fitting the experimental photoabsorption cross-sections. One is based on the microscopic relativistic quasiparticle random phase approximation approach, whereas the other is estimated by the phenomenological models within the Lorentzian representation. Both of them are demonstrated ot efficiently describe the experimental photoabsorption cross-sections available for medium to heavy-mass nuclei, and they can obtain more reliable predictions for the unknown nuclear system.
The X(4140) and X(4160) resonances in the $ {{e^+e^-\to \gamma J/\psi \phi}}$ reaction
En Wang, Ju-Jun Xie, Li-Sheng Geng, Eulogio Oset
Published: , doi: 10.1088/1674-1137/43/11/113101
We investigate the $ J/\psi \phi $ invariant mass distribution in the $ e^+e^-\to \gamma J/\psi\phi $ reaction at a center-of-mass energy of $ \sqrt{s} = 4.6 $ GeV measured by the BESIII collaboration, which concluded that no significant signals were observed for $ e^+e^- \to \gamma X(4140) $ because of the low statistics. We show, however, that the $ J/\psi \phi $ invariant mass distribution is compatible with the existence of the $ X(4140) $ state, appearing as a peak, and a strong cusp structure at the $ D^*_s\bar{D}^*_s $ threshold, resulting from the molecular nature of the $ X(4160) $ state, which provides a substantial contribution to the reaction. This is consistent with our previous analysis of the $ B^+\to J/\psi\phi K^+ $ decay measured by the LHCb collaboration. We strongly suggest further measurements of this process with more statistics to clarify the nature of the $ X(4140) $ and $ X(4160) $ resonances.
A pattern for the flavor dependent quark-antiquark interaction
Muyang Chen, Lei Chang
Published: , doi: 10.1088/1674-1137/43/11/114103
A flavor dependent kernel is constructed based on the rainbow-ladder truncation of the Dyson-Schwinger and Bethe-Salpeter equations in quantum chromodynamics. The quark-antiquark interaction is composed of a flavor dependent infrared part and a flavor independent ultraviolet part. Our model gives a successful and unified description of the light, heavy and heavy-light ground state pseudoscalar and vector mesons. Our model shows, for the first time, that the infrared enhanced quark-antiquark interaction is stronger and wider for lighter quarks.
An alternative approach to thermodynamic phase transitions
Seyed Hossein Hendi, Shahram Panahiyan, Behzad Eslam Panah, Mubasher Jamil
Published: , doi: 10.1088/1674-1137/43/10/103105
One of the major open problems in theoretical physics is a consistent quantum gravity theory. Recent developments in thermodynamic phase transitions of black holes and their van der Waals-like behavior may provide an interesting quantum interpretation of classical gravity. Studying different methods of investigating phase transitions can extend our insight into the nature of quantum gravity. In this paper, we present an alternative theoretical approach for finding thermodynamic phase transitions in the extended phase space. Unlike the standard methods based on the usual equation of state involving temperature, our approach uses a new quasi-equation constructed from the slope of temperature versus entropy. This approach addresses some of the shortcomings of the other methods, and provides a simple and powerful way of studying the critical behavior of a thermodynamical system. Among the applications of this approach, we emphasize the analytical demonstration of possible phase transition points, and the identification of the non-physical range of horizon radii for black holes.