Chinese Physics C

2024-3 Contents

2024, 48(3): 1-2.

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Abstract:

Time-reversal asymmetries in $ {\boldsymbol\Lambda_{\boldsymbol b} {\bf\to} {\boldsymbol\Lambda}{\bf (\to}{\boldsymbol p} \boldsymbol\pi^{\bf -}{\bf)}\boldsymbol\ell^{\bf +}\boldsymbol\ell^{\bf -} }$

Chao-Qiang Geng, Chia-Wei Liu, Zheng-Yi Wei

2024, 48(3): 033101. doi: 10.1088/1674-1137/ad13f6

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Abstract:
We study the decays of

\begin{document}$ \Lambda_b \to \Lambda(\to p \pi^-) \ell ^+ \ell^- $\end{document}

with

\begin{document}$ \ell = (e, \mu, \tau) $\end{document}

. We examine the full angular distributions with polarized

\begin{document}$ \Lambda_b $\end{document}

, where the T-odd observables are identified. We discuss the possible effects of new physics (NP) and find that the T-odd observables are sensitive to them as they vanish in the standard model. Special attention is given to the interference of (pseudo)scalar operators with (axial)vector operators in polarized

\begin{document}$ \Lambda_b \to \Lambda(\to p \pi^-) \tau^+ \tau^- $\end{document}

, which are studied for the first time. Their effects are proportional to the lepton masses and therefore may evade the constraint from

\begin{document}$ \Lambda_b \to \Lambda(\to p \pi^-) \mu^+ \mu^- $\end{document}

at the LHCb naturally. As

\begin{document}$ \Lambda_b \to \Lambda(\to p \pi^-) \tau^+ \tau^- $\end{document}

is uncontaminated by the charmonia resonance, it provides a clean background to probe NP. In addition, we show that the experimental central value of

\begin{document}$ K_{10} $\end{document}

in

\begin{document}$ \Lambda_b \to \Lambda(\to p \pi^-) \mu^+ \mu^- $\end{document}

at the LHCb can be explained by the NP case, which couples to the right-handed quarks and leptons. The polarization fraction of

\begin{document}$ \Lambda_b $\end{document}

at the LHCb is found to be consistent with zero regardless of the NP scenarios.

J/ψ pair hadroproduction at next-to-leading order in nonrelativistic-QCD at ATLAS

Li-Ping Sun

2024, 48(3): 033102. doi: 10.1088/1674-1137/ad1a98

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Abstract:
We present a complete study on the

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

pair hadroproduction at next-to-leading order (NLO) in the nonrelativstic-QCD (NRQCD) framework with the pair of

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

in either

\begin{document}$ {}^{3}S_1^{[1]} $\end{document}

or

\begin{document}$ {}^{1}S_0^{[8]} $\end{document}

fock state. We found that the contribution of the

\begin{document}$ {}^{1}S_0^{[8]} $\end{document}

channel at NLO is essential, and for ATLAS, the NRQCD results can describe the experimental data to a certain extent.

Solving the strong CP problem via a ${ \bar{\boldsymbol\theta} }$-characterized mirror symmetry

Pei-Hong Gu

2024, 48(3): 033103. doi: 10.1088/1674-1137/ad102b

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Abstract:
In the standard model QCD Lagrangian, a term of CP violating gluon density is theoretically expected to have a physical coefficient

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

, which is typically on the order of unity. However, the upper bound on the electric dipole moment of the neutron enforces the value of

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

to be extremely small. The significant discrepancy between theoretical expectations and experimental results in this context is widely recognized as the strong CP problem. To solve this puzzle in an appealing context of two Higgs doublets, we propose a

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

-characterized mirror symmetry between two Higgs singlets with respective discrete symmetries. In our scenario, the parameter

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

can completely disappear from the full Lagrangian after the standard model fermions take a proper phase rotation as well as the Higgs doublets and singlets. Moreover, all of new physics for solving the strong CP problem can be allowed near the TeV scale.

Fully-light vector tetraquark states with explicit P-wave via QCD sum rules

Qi Xin, Zhi-Gang Wang

2024, 48(3): 033104. doi: 10.1088/1674-1137/ad181c

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Abstract:
In this study, we apply the QCD sum rules to investigate the vector fully-light tetraquark states with an explicit P-wave between the diquark and antidiquark pairs. We observed that the

\begin{document}$ C\gamma_\alpha\otimes\stackrel{\leftrightarrow}{\partial}_\mu\otimes\gamma^\alpha C $\end{document}

(or

\begin{document}$ C\gamma_\alpha\otimes\stackrel{\leftrightarrow}D_\mu\otimes\gamma^\alpha C $\end{document}

) type current with fully-strange quarks couples potentially to a tetraquark state with a mass

\begin{document}$ 2.16 \pm 0.14 \,{\rm{GeV}} $\end{document}

, which supports assigning

\begin{document}$ Y(2175)/\phi(2170) $\end{document}

as the diquark-antidiquark type tetraquark state with

\begin{document}$J^{PC}=1^{--}$\end{document}

. The

\begin{document}$ qs\bar{q}\bar{s} $\end{document}

and

\begin{document}$ ss\bar{s}\bar{s} $\end{document}

vector tetraquark states with the structure

\begin{document}$ C\gamma_\mu\otimes \stackrel{\leftrightarrow}{\partial}_\alpha \otimes\gamma^\alpha C + C\gamma^\alpha \otimes\stackrel{\leftrightarrow}{\partial}_\alpha \otimes\gamma_\mu $\end{document}

(or

\begin{document}$ C\gamma_\mu\otimes \stackrel{\leftrightarrow}D_\alpha \otimes\gamma^\alpha C + C\gamma^\alpha \otimes\stackrel{\leftrightarrow}D_\alpha \otimes\gamma_\mu $\end{document}

) are consistent with

\begin{document}$ X(2200) $\end{document}

and

\begin{document}$ X(2400) $\end{document}

, respectively, which lie in the region from

\begin{document}$ 2.20 $\end{document}

to

\begin{document}$ 2.40\,{\rm{GeV}} $\end{document}

. The central values of the masses of the fully-strange vector tetraquark states with an explicit P-wave are approximately

\begin{document}$ 2.16-3.13\,{\rm{GeV}} $\end{document}

(or

\begin{document}$ 2.16-3.16\,{\rm{GeV}} $\end{document}

). Predictions for other fully-light vector tetraquark states with and without hidden-strange are also presented.

Influence of low-energy supersymmetric vector-like quirk particles on W mass increment and muon g–2 anomaly

Ping Zhou

2024, 48(3): 033105. doi: 10.1088/1674-1137/ad13f5

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Abstract:
In the low energy realization of the quirk assisted Standard Model, the couplings between the exotic particles "quirks" and gauge bosons may contribute to the W mass and muon

\begin{document}$ g-2 $\end{document}

anomaly reported by FermiLab. We calculate the contributions from supersymmetric quirk particles as an example. By imposing the theoretical constraints, we determined that the CDF II W-boson mass increment strictly constrains the mixing and coupling parameters and the quirk mass

\begin{document}$ m_F $\end{document}

, while the muon

\begin{document}$ g-2 $\end{document}

anomaly cannot be solely attributed to the involvement of exotic particles, considering their significantly large masses.

Reconstructing parton distribution function based on maximum entropy method

Sihan Zhang, Xiaobin Wang, Tao Lin, Lei Chang

2024, 48(3): 033106. doi: 10.1088/1674-1137/ad1b3d

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Abstract:
A new method based on the maximum entropy principle for reconstructing the parton distribution function (PDF) from moments is proposed. Unlike traditional methods, the new method does not require any artificial assumptions. For the case of moments with errors, we introduce Gaussian functions to soften the constraints of moments. Through a series of tests, the effectiveness and reconstruction efficiency of this new method are evaluated comprehensively, demonstrating that this method is reasonable and can achieve high-quality reconstruction with at least the first six moments as input. Finally, we select a set of lattice quantum chromodynamics (QCD) results regarding moments as input and provide reasonable reconstruction results for the pion.

Nonlinear corrections for the nuclear gluon distribution in eA processes

G.R. Boroun, B. Rezaei, F. Abdi

2024, 48(3): 033107. doi: 10.1088/1674-1137/ad1cdb

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Abstract:
An analytical study with respect to the nonlinear corrections for the nuclear gluon distribution function in the next-to-leading order approximation at small x is presented. We consider the nonlinear corrections to the nuclear gluon distribution functions at low values of x and

\begin{document}$ Q^{2} $\end{document}

using the parametrization

\begin{document}$ F_{2}(x,Q^{2}) $\end{document}

and the nuclear modification factors obtained from the Khanpour-Soleymaninia-Atashbar-Spiesberger-Guzey model. The CT18 gluon distribution is used for the baseline proton gluon density at

\begin{document}$ Q_{0}^{2}=1.69\; {\rm{GeV}}^2 $\end{document}

. We discuss the behavior of the gluon densities in the next-to-leading order and the next-to-next-to-leading order approximations at the initial scale

\begin{document}$ Q_{0}^{2} $\end{document}

, as well as the modifications due to the nonlinear corrections. We find that the QCD nonlinear corrections are more significant for the next-to-leading order accuracy than the next-to-next-to-leading order for light and heavy nuclei. The results of the nonlinear GLR-MQ evolution equation are similar to those obtained with the Rausch-Guzey-Klasen gluon upward and downward evolutions within the uncertainties. The magnitude of the gluon distribution with the nonlinear corrections increases with a decrease in x and an increase in atomic number A.

Elastic scattering of ¹³C and ¹⁴C isotopes on a ²⁰⁸Pb target at energies of approximately five times the Coulomb barriers

Guo Yang, Fang-Fang Duan, Kang Wang, Yan-Yun Yang, Zhi-Yu Sun, Valdir Guimarães, Dan-Yang Pang, Wen-Di Chen, Lei Jin, Shi-Wei Xu, Jun-Bing Ma, Peng Ma, Zhen Bai, Ling-Hao Wang, Quan Liu, Hooi-Jin Ong, Bing-Feng Lv, Song Guo, Mukhi Kumar Raju, Xiu-Hua Wang, Rong-Hua Li, Yu-Hu Zhang, Xiao-Hong Zhou, Zheng-Guo Hu, Hu-Shan Xu

2024, 48(3): 034001. doi: 10.1088/1674-1137/ad1678

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Abstract:
The elastic scattering angular distributions of

\begin{document}$ ^{13} $\end{document}

C at 340 MeV and

\begin{document}$ ^{14} $\end{document}

C at 294 MeV and 342 MeV on a

\begin{document}$ ^{208} $\end{document}

Pb target, which correspond to approximately five times the Coulomb barriers, were measured at the Radioactive Ion Beam Line in Lanzhou. The data were analyzed within the optical model and continuum-discretized coupled-channels (CDCC) framework, and the results of both calculations could effectively account for the experimental data. The differential cross sections of elastic scattering revealed no particular suppression at the Coulomb nuclear interference peak angles, suggesting that the breakup coupling effects on the elastic scattering angular distributions were negligibly small in this incident energy region. The contributions from the couplings with inelastic states to the elastic cross sections were of minor importance within the angular range covered by these experiments.

Ground-state mass of ²²Al and test of state-of-the-art ab initio calculations

M.Z. Sun, Y. Yu, X.P. Wang, M. Wang, J.G. Li, Y.H. Zhang, K. Blaum, Z.Y. Chen, R.J. Chen, H.Y. Deng, C.Y. Fu, W.W. Ge, W.J. Huang, H.Y. Jiao, H.H. Li, H.F. Li, Y.F. Luo, T. Liao, Yu.A. Litvinov, M. Si, P. Shuai, J.Y. Shi, Q. Wang, Y.M. Xing, X. Xu, H.S. Xu, F.R. Xu, Q. Yuan, T. Yamaguchi, X.L. Yan, J.C. Yang, Y.J. Yuan, X.H. Zhou, X. Zhou, M. Zhang, Q. Zeng

2024, 48(3): 034002. doi: 10.1088/1674-1137/ad1a0a

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Abstract:
The ground-state mass excess of the

\begin{document}$ T_{z}=-2 $\end{document}

drip-line nucleus