Chinese Physics C

Searching for neutrino-less double beta decay 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

2019, 43(11): 113001. doi: 10.1088/1674-1137/43/11/113001

HTML

PDF

Abstract:
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

\begin{document}$ \times 10^{23} $\end{document}

yr at the 90% confidence level, which corresponds to an effective Majorana neutrino mass

\begin{document}$m_{\beta \beta} < (1.4 - 3.7)$\end{document}

eV. This is the first NLDBD result reported from a dual-phase xenon experiment.

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

2019, 43(11): 113101. doi: 10.1088/1674-1137/43/11/113101

HTML

PDF

Abstract:
We investigate the

\begin{document}$ J/\psi \phi $\end{document}

invariant mass distribution in the

\begin{document}$ e^+e^-\to \gamma J/\psi\phi $\end{document}

reaction at a center-of-mass energy of

\begin{document}$ \sqrt{s} = 4.6 $\end{document}

GeV measured by the BESIII collaboration, which concluded that no significant signals were observed for

\begin{document}$ e^+e^- \to \gamma X(4140) $\end{document}

because of the low statistics. We show, however, that the

\begin{document}$ J/\psi \phi $\end{document}

invariant mass distribution is compatible with the existence of the

\begin{document}$ X(4140) $\end{document}

state, appearing as a peak, and a strong cusp structure at the

\begin{document}$ D^*_s\bar{D}^*_s $\end{document}

threshold, resulting from the molecular nature of the

\begin{document}$ X(4160) $\end{document}

state, which provides a substantial contribution to the reaction. This is consistent with our previous analysis of the

\begin{document}$ B^+\to J/\psi\phi K^+ $\end{document}

decay measured by the LHCb collaboration. We strongly suggest further measurements of this process with more statistics to clarify the nature of the

\begin{document}$ X(4140) $\end{document}

and

\begin{document}$ X(4160) $\end{document}

resonances.

Simplified dark matter models with loop effects in direct detection and the constraints from indirect detection and collider search

Tong Li, Peiwen Wu

2019, 43(11): 113102. doi: 10.1088/1674-1137/43/11/113102

HTML

PDF

Abstract:
We reexamine the simplified dark matter (DM) models with fermionic DM particle and spin-0 mediator. The DM-nucleon scattering cross sections in these models are low-momentum suppressed at tree-level, but receive sizable loop-induced spin-independent contribution. We perform one-loop calculations for scalar-type and twist-2 DM-quark operators, and complete two-loop calculations for scalar-type DM-gluon operator. Analyzing the loop-level contribution from new operators, we find that future direct detection experiments could be sensitive to a fraction of the parameter space. The indirect detection and collider search also provide complementary constraints on these models.

Drag force on heavy quarks from holographic QCD

Yuanhui Xiong, Xingzheng Tang, Zhongjie Luo

2019, 43(11): 113103. doi: 10.1088/1674-1137/43/11/113103

HTML

PDF

Abstract:
We study the drag force of a relativistic heavy quark using a holographic QCD model with conformal invariance broken by a background dilaton. The effects of the chemical potential and the confining scale on this quantity are analyzed. The drag force in this model is shown to be larger than that of

\begin{document}${\cal N}=4$\end{document}

supersymmetric Yang-Mills (SYM) plasma. In particular, the inclusion of the chemical potential and confining scale both enhance the drag force, in agreement with earlier findings. Moreover, we discuss how the chemical potential and confining scale influence the diffusion coefficient.

Probing the top quark flavor-changing couplings at CEPC

Liaoshan Shi, Cen Zhang

2019, 43(11): 113104. doi: 10.1088/1674-1137/43/11/113104

HTML

PDF

Abstract:
We propose to study the flavor properties of the top quark at the future Circular Electron Positron Collider (CEPC) in China. We systematically consider the full set of 56 real parameters that characterize the flavor-changing neutral interactions of the top quark, which can be tested at CEPC in the single top production channel. Compared with the current bounds from the LEP2 data and the projected limits at the high-luminosity LHC, we find that CEPC could improve the limits of the four-fermion flavor-changing coefficients by one to two orders of magnitude, and would also provide similar sensitivity for the two-fermion flavor-changing coefficients. Overall, CEPC could explore a large fraction of currently allowed parameter space that will not be covered by the LHC upgrade. We show that the c-jet tagging capacity at CEPC could further improve its sensitivity to top-charm flavor-changing couplings. If a signal is observed, the kinematic distribution as well as the c-jet tagging could be exploited to pinpoint the various flavor-changing couplings, providing valuable information about the flavor properties of the top quark.

A possible explanation of the threshold enhancement in the process $ {{e^+e^-\rightarrow \Lambda\bar{\Lambda} }}$

Li-Ye Xiao, Xin-Zhen Weng, Xian-Hui Zhong, Shi-Lin Zhu

2019, 43(11): 113105. doi: 10.1088/1674-1137/43/11/113105

HTML

PDF

Abstract:
Inspired by the recent measurement of the process

\begin{document}$ e^+e^-\rightarrow \Lambda\bar{\Lambda} $\end{document}

, we calculate the mass spectrum of the

\begin{document}$ \phi $\end{document}

meson with the GI model. For the excited vector strangeonium states

\begin{document}$ \phi(3S,\; 4S,\; 5S,\; 6S) $\end{document}

and

\begin{document}$ \phi(2D,\; 3D,\; 4D,\; 5D) $\end{document}

, we investigate the electronic decay width with the Van Royen-Weisskopf formula, and the partial widths of the

\begin{document}$ \Lambda\bar{\Lambda} $\end{document}

,

\begin{document}$ \Xi^{-(*)}\bar{\Xi}^+ $\end{document}

, and

\begin{document}$ \Sigma^{+(*)}\bar{\Sigma}^{-(*)} $\end{document}

decay modes with the extended quark-pair creation model. We find that the electronic decay width of the

\begin{document}$ D $\end{document}

-wave vector strangeonium is about

\begin{document}$ 3\sim8 $\end{document}

times larger than of the

\begin{document}$ S $\end{document}

-wave vector strangeonium. Around 2232 MeV, the partial decay width of the

\begin{document}$ \Lambda\bar{\Lambda} $\end{document}

mode can be up to several MeV for

\begin{document}$ \phi(3^3S_1) $\end{document}

, while the partial

\begin{document}$ \Lambda\bar{\Lambda} $\end{document}

decay width of

\begin{document}$ \phi(2^3D_1) $\end{document}

is

\begin{document}$ {\cal{O}}(10^{-3}) $\end{document}

keV. If the threshold enhancement reported by the BESIII collaboration arises from the strangeonium meson, this state is very likely the

\begin{document}$ \phi(3^3S_1) $\end{document}

state. We also note that the

\begin{document}$ \Lambda\bar{\Lambda} $\end{document}

and

\begin{document}$ \Sigma^{+}\bar{\Sigma}^{-} $\end{document}

partial decay widths of the states

\begin{document}$ \phi(3^3D_1) $\end{document}

and

\begin{document}$ \phi(4^3S_1) $\end{document}

are several MeV, which is sufficient to be observed in future experiments.

Alternative approach to thermodynamic phase transitions

Seyed Hossein Hendi, Shahram Panahiyan, Behzad Eslam Panah, Mubasher Jamil

2019, 43(11): 113106. doi: 10.1088/1674-1137/43/11/113106

HTML

PDF

Abstract:
One of the major open problems in theoretical physics is the lack of a consistent quantum gravity theory. Recent developments in our knowledge on 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 understanding of 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.

Tensor force effect on the exotic structure of neutron-rich Ca isotopes

Yan-Zhao Wang, Xue-Dou Su, Chong Qi, Jian-Zhong Gu

2019, 43(11): 114101. doi: 10.1088/1674-1137/43/11/114101

HTML

PDF

Abstract:
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.

Giant dipole resonance parameters from photoabsorption cross-sections

Yuan Tian, Xi Tao, Jimin Wang, Xianbo Ke, Ruirui Xu, Zhigang Ge

2019, 43(11): 114102. doi: 10.1088/1674-1137/43/11/114102

HTML

PDF

Abstract:
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 (

\begin{document}$\sigma_{\rm abs}$\end{document}

).

\begin{document}$\sigma_{\rm abs}$\end{document}

is dominated by the electric giant dipole resonance at

\begin{document}$\gamma$\end{document}

energy

\begin{document}$\epsilon_\gamma \leqslant 40$\end{document}

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.

A pattern for the flavor dependent quark-antiquark interaction

Muyang Chen, Lei Chang

2019, 43(11): 114103. doi: 10.1088/1674-1137/43/11/114103

HTML

PDF

Abstract:
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.

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

2019, 43(11): 114104. doi: 10.1088/1674-1137/43/11/114104

HTML

PDF

Abstract:

\begin{document}$ \beta $\end{document}

-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

\begin{document}$ \beta $\end{document}

-decay life, which limits the resolution of the predicted

\begin{document}$ \beta $\end{document}

-decay half-life. We systematically study the contribution of the first forbidden (FF) transitions to the