Chinese Physics C

Towards the establishment of the light J^{P (C )}=1^–(+) hybrid nonet

Lin Qiu, Qiang Zhao

2022, 46(5): 051001. doi: 10.1088/1674-1137/ac567e

HTML

PDF

Abstract:
The observation of the light hybrid candidate

\begin{document}$ \eta_1(1855) $\end{document}

by the BESIII Collaboration offers great opportunities for advancing our knowledge on exotic hadrons in terms of flavor sector. We demonstrate that this observation provides a crucial clue for establishing the

\begin{document}$ J^{P(C)}=1^{-(+)} $\end{document}

hybrid nonet. Based on the flux tube model picture, the production and decay mechanisms for the

\begin{document}$ J^{P(C)}=1^{-(+)} $\end{document}

hybrid nonet in the

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

radiative decays into two pseudoscalar mesons are investigated. In the

\begin{document}$ I=0 $\end{document}

sector, we deduce that the SU(3) flavor octet and singlet mixing is non-negligible and apparently deviates from the flavor ideal mixing. Because only signals for one isoscalar

\begin{document}$ \eta_1(1855) $\end{document}

are observed in the

\begin{document}$ \eta\eta' $\end{document}

channel, we investigate two schemes of the nonet structure in which

\begin{document}$ \eta_1(1855) $\end{document}

can either be the higher or lower mass state that strongly couples to

\begin{document}$ \eta\eta' $\end{document}

. Possible channels for detecting the multiplets are suggested. In particular, a combined analysis of the hybrid production in

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

, where

\begin{document}$ V $\end{document}

and

\begin{document}$ H $\end{document}

denote the light vector mesons and

\begin{document}$ 1^{-(+)} $\end{document}

hybrid states, respectively, may provide further evidence for this nonet structure and ultimately establish these mysterious exotic species in the experiment.

Linear seesaw model with a modular S₄ flavor symmetry

Takaaki Nomura, Hiroshi Okada

2022, 46(5): 053101. doi: 10.1088/1674-1137/ac4975

HTML

PDF

Abstract:
We discuss a linear seesaw model with a field content as minimum as possible, introducing a modular

\begin{document}$ S_4 $\end{document}

using gauged

\begin{document}$ U(1)_{B-L} $\end{document}

symmetries. Owing to the rank two neutrino mass matrix, we obtain a vanishing neutrino mass eigenvalue, and only the normal mass hierarchy of neutrinos is favored via the modular

\begin{document}$ S_4 $\end{document}

symmetry. In our numerical

\begin{document}$ \Delta \chi^2 $\end{document}

analysis, we especially determine a relatively sharp prediction on the sum of neutrino masses to be approximately

\begin{document}$ 60 $\end{document}

meV, in addition to other predictions.

Lattice calculation of χ_c0 → 2γ decay width

Zuoheng Zou, Yu Meng, Chuan Liu

2022, 46(5): 053102. doi: 10.1088/1674-1137/ac4bcc

HTML

PDF

Abstract:
We perform a lattice QCD calculation of the

\begin{document}$ \chi_{c0} \rightarrow 2\gamma $\end{document}

decay width using a model-independent method that does not require the momentum extrapolation of corresponding off-shell form factors. The simulation is performed on ensembles of

\begin{document}$ N_f = 2 $\end{document}

twisted mass lattice QCD gauge configurations with three different lattice spacings. After the continuum extrapolation, the decay width is obtained to be

\begin{document}$ \Gamma_{\gamma\gamma}(\chi_{c0}) = 3.65(83)_{\mathrm{stat}}(21)_{\mathrm{lat.syst}}(66)_{\mathrm{syst}}\, \rm{keV} $\end{document}

. Regardless of this large statistical error, our result is compatible with the experimental results within 1.3σ. Potential improvements of the lattice calculation in the future are also discussed.

$ {\boldsymbol B_c \to \boldsymbol J/\boldsymbol\psi }$ helicity form factors and the $ {\boldsymbol B_{\boldsymbol c}^+ \to \boldsymbol J/\boldsymbol\psi+\boldsymbol(P, V, \boldsymbol\ell^+ \boldsymbol\nu_{\boldsymbol\ell}) }$ decays

Wei Cheng, Yi Zhang, Long Zeng, Hai-Bing Fu, Xing-Gang Wu

2022, 46(5): 053103. doi: 10.1088/1674-1137/ac4c9f

HTML

PDF

Abstract:
In this paper, we calculate the

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

helicity form factors (HFFs) up to twist-4 accuracy by using the light-cone sum rules (LCSR) approach. After extrapolating those HFFs to the physically allowable

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

region, we investigate the

\begin{document}$ B^+_c $\end{document}

-meson two-body decays and semi-leptonic decays

\begin{document}$ B_c^+ \to J/\psi+(P, V, \ell^+ \nu_\ell) $\end{document}

, where

\begin{document}$ P/V $\end{document}

stand for light pseudoscalar and vector mesons, respectively. The branching fractions can be derived using the CKM matrix element and the

\begin{document}$ B_c $\end{document}

lifetime from the Particle Data Group, and we obtain

\begin{document}${\cal{B}}(B_c^+ \to J/\psi \pi^+) = (0.136^{+0.002}_{-0.002}){\text{%}}$\end{document}

,

\begin{document}${\cal{B}}(B_c^+ \to $\end{document}

\begin{document}$ J/\psi K^+) = (0.010^{+0.000}_{-0.000}){\text{%}}$\end{document}

,

\begin{document}$ {\cal{B}}(B_c^+ \to J/\psi \rho^+) = (0.768^{+0.029}_{-0.033}){\text{%}} $\end{document}

,

\begin{document}$ {\cal{B}}(B_c^+ \to J/\psi K^{\ast +}) = (0.043^{+0.001}_{-0.001}){\text{%}} $\end{document}

,

\begin{document}${\cal{B}}(B_c^+ \to $\end{document}

\begin{document}$ J/\psi \mu^+\nu_\mu) = (2.802^{+0.526}_{-0.675}){\text{%}}$\end{document}

and

\begin{document}$ {\cal{B}}(B_c^+ \to J/\psi \tau^+\nu_\tau) = (0.559^{+0.131}_{-0.170}){\text{%}} $\end{document}

. We then obtain

\begin{document}${\cal{R}}_{\pi^+/\mu^+\nu_\mu} = 0.048^{+ 0.009}_{-0.012}$\end{document}

and

\begin{document}$ {\cal{R}}_{K^+ / \pi^+} = 0.075^{+0.005}_{-0.005} $\end{document}

, which agree with the LHCb measured value within

\begin{document}$ 1\sigma $\end{document}

-error. We also obtain

\begin{document}$ {\cal{R}}_{J/\psi} = 0.199^{+ 0.060}_{-0.077} $\end{document}

, which like other theoretical predictions, is consistent with the LHCb measured value within

\begin{document}$ 2\sigma $\end{document}

-error. These imply that the HFFs under the LCSR approach are also applicable to the

\begin{document}$ B^+_c $\end{document}

meson two-body decays and semi-leptonic decays

\begin{document}$ B_c^+ \to J/\psi+(P, V, \ell^+ \nu_\ell) $\end{document}

, and the HFFs obtained using LCSR in a new way implies that there may be new physics in the

\begin{document}$ B_c\to J/\psi \ell^+ \nu_\ell $\end{document}

semi-leptonic decays.

Resonances ρ(1450)⁺ and ρ(1700)⁺ in B → DKK decays

Ai-Jun Ma, Wen-Fei Wang

2022, 46(5): 053104. doi: 10.1088/1674-1137/ac4cb5

HTML

PDF

Abstract:
The contributions for the kaon pair from the intermediate states

\begin{document}$ \rho(1450)^+ $\end{document}

and

\begin{document}$ \rho(1700)^+ $\end{document}

in the decays

\begin{document}$ B^+ \to \bar{D}^0 K^+ \bar{K}^0 $\end{document}

,

\begin{document}$ B^0 \to D^- K^+ \bar{K}^0 $\end{document}

, and

\begin{document}$ B_s^0 \to D_s^-K^+ \bar{K}^0 $\end{document}

are analyzed within the perturbative QCD factorization approach. The decay amplitudes for all concerned decays in this work are dominated by the factorizable Feynman diagrams with the emission of the kaon pair, and the charged ρ mesons should be of great importance in the

\begin{document}$ KK $\end{document}

channel of the related three-body B decays. Moreover, these quasi-two-body decays are CKM-favored, and the relevant branching ratios are predicted to be in the order of

\begin{document}$ 10^{-5} $\end{document}

, which have the potential to be measured by experiments. It is also shown that the contributions of the subprocesses

\begin{document}$ \rho(1450, 1700)^+ \to KK $\end{document}

for the three-body B meson decays are considerable according to the total three-body branching fractions presented by Belle. Therefore, the decays

\begin{document}$ B^+ \to \bar{D}^0 K^+ \bar{K}^0 $\end{document}

,

\begin{document}$ B^0 \to D^- K^+ \bar{K}^0 $\end{document}

, and

\begin{document}$ B_s^0 \to D_s^-K^+ \bar{K}^0 $\end{document}

can be employed to study the properties of

\begin{document}$ \rho(1450) $\end{document}

and

\begin{document}$ \rho(1700) $\end{document}

in the LHCb and Belle-II experiments.

Photoproduction ${ \boldsymbol\gamma \boldsymbol p \boldsymbol \to {\boldsymbol K}^+\boldsymbol\Lambda{\boldsymbol{(1690)}} }$ in an effective Lagrangian approach

Neng-Chang Wei, Ai-Chao Wang, Fei Huang

2022, 46(5): 053105. doi: 10.1088/1674-1137/ac4e7c

HTML

PDF

Abstract:
A gauge-invariant model is constructed for the

\begin{document}$ \gamma p \to K^+\Lambda(1690) $\end{document}

reaction within a tree-level effective Lagrangian approach to understand the underlying production mechanisms and study the resonance contributions in this reaction. In addition to the t-channel K and

\begin{document}$ K^\ast $\end{document}

exchanges, s-channel nucleon exchange, and interaction current, the s-channel nucleon resonance exchanges are included in constructing the reaction amplitudes to describe the data. It is found that the contributions from the s-channel

\begin{document}$ N(2570)5/2^- $\end{document}

exchange are required to describe the most recently measured total cross-section data for

\begin{document}$ \gamma p \to K^+\Lambda(1690) $\end{document}

from the CLAS Collaboration. Further analysis indicates that the interaction current dominates the

\begin{document}$ \gamma p \to K^+\Lambda(1690) $\end{document}

reaction near the threshold as a result of gauge invariance. The t-channel K exchange contributes significantly, while the contributions from the t-channel

\begin{document}$ K^\ast $\end{document}

exchange and s-channel nucleon exchange are ultimately negligible. The contributions from the s-channel

\begin{document}$ N(2570)5/2^- $\end{document}

exchange are found to be responsible for the bump structure shown in the CLAS total cross-section data above the center-of-mass energy

\begin{document}$ W \approx 2.7 $\end{document}

GeV. The predictions of the differential cross sections for

\begin{document}$ \gamma p \to K^+\Lambda(1690) $\end{document}

are presented and discussed, which can provide theoretical guidance for future experiments.

Investigating the Z' gauge boson at future lepton colliders

Xinyue Yin, Honglei Li, Yi Jin, Zhilong Han, Zongyang Lu

2022, 46(5): 053106. doi: 10.1088/1674-1137/ac500e

HTML

PDF

Abstract: