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Si-Qiang Luo

Publications and source records attributed to Si-Qiang Luo.

44 records · Page 3Linked to original sources

Universal behavior of mass gaps existing in the single heavy baryon family

The mass gaps existing in the discovered single heavy flavor baryons are analyzed, which show some universal behaviors. Under the framework of a constituent quark model, we quantitatively explain why such interesting phenomenon happens, when these established excited heavy baryons are regarded as the $λ$-mode excitations. Based on the universal behaviors of the discussed mass gaps, we may have three implications including the prediction of the masses of excited $Ξ_b^0$ baryons which are still missing in the experiment. For completeness, we also discuss the mass gaps of these $ρ$-mode excited single heavy flavor baryons.

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Predicting a new resonance as charmed-strange baryonic analog of $D_{s0}^*(2317)$

By an unquenched quark model, we predict a charmed-strange baryon state, namely, the $Ω_{c0}^d(1P,1/2^-)$. Its mass is predicted to be 2945 MeV, which is below the $Ξ_c\bar{K}$ threshold due to the nontrivial coupled-channel effect. So the $Ω_{c0}^d(1P,1/2^-)$ state could be regraded as the analog of the charmed-strange meson $D_{s0}^*(2317)$. It is a good opportunity for the running Belle II experiment to search for this state in the $Ω_c^{(*)}γ$ mass spectrum experiment in the future.

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Resolving the low mass puzzle of $Λ_c(2940)^+$

For the long standing low mass puzzle of $Λ_c(2940)^+$, we propose an unquenched picture. Our calculation explicitly shows that the mass of the $Λ_c(2P,3/2^-)$ state can be lowered down to be consistent with the experimental data of $Λ_c(2940)^+$ by introducing the $D^*N$ channel contribution. Additionally, we give a semi-quantitative analysis to illustrate why the $Λ_c(2940)^+$ state has a narrow width. It means that the low mass puzzle of $Λ_c(2940)^+$ can be solved. What is more important is that we predict a mass inversion relation for the $2P$ $Λ_{c}^+$ states, i.e., the $Λ_c(2P,1/2^-)$ state is higher than the $Λ_c(2P,3/2^-)$, which is totally different from the result of conventional quenched quark model. It provides a criterion to test such an unquenched scenario for $Λ_c(2940)^+$. We expect the future experimental progress from the LHCb and Belle II.

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Possibility of charmoniumlike state $X(3915)$ as $χ_{c0}(2P)$ state

In this work, we seriously discuss whether $X(3915)$ can be treated as a $χ_{c0}(2P)$ state. Based on an unquenched quark model, we give the mass spectrum of the $χ_{cJ}(2P)$ states, where there are no free input parameters in our calculation. Our result shows that the mass gap between $χ_{c0}(2P)$ and $χ_{c2}(2P)$ can reach 13 MeV, which can reproduce the mass difference between $Z(3930)$ and $X(3915)$. Additionally, the calculated masses of $χ_{c0}(2P)$ and $χ_{c2}(2P)$ are consistent with experimental values of $X(3915)$ and $Z(3930)$, respectively. Besides, giving the mass spectrum analysis to support $X(3915)$ as $χ_{c0}(2P)$, we also calculate the width of $χ_{c0}(2P)$ with the same framework, which is also consistent with the experimental data of $X(3915)$. Thus, the possibility of charmoniumlike state $X(3915)$ as $χ_{c0}(2P)$ state is further enforced.

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Studying $X(2100)$ hadronic decays and predicting its pion and kaon induced productions

The newly observed $X(2100)$ by the BESIII Collaboration inspires our interest in studying the light meson system, especially axial-vector mesons. Since the $X(2100)$ has $J^P=1^+$ possibilities but cannot be distinguished only by mass, we make use of flux-tube model to study the strong decay behavior of $X(2100)$ under this assignment. The experimental width of the newly reported $X(2100)$ can be reproduced in our calculation, which favors an assignment of $X(2100)$ as the second radial excitation of $h_1(1380)$ with $I(J^P)=0(1^+)$. And the $\mathcal{B}(X(2100)\to ϕη^\prime)$ has a sizable contribution to the total width. Furthermore, we focus on the production of $X(2100)$ and its flavour partner $h_1(1965)$ induced by pion and kaon on a proton target with the Feynman model and the Regge model, which is an available platform to further identify their nature. The numerical results indicate that the total cross section are similar in the two models. When the range of momentum ${\mathrm{p_{Lab}}}$ is 10 to 30 GeV/$c$, the total cross sections for $π^-p\to X(2100)n$ and $K^-p\to X(2100)Λ$ are predicted to be at an order of magnitude of 0.1 $μ$b. Whereas, the total cross section for $π^-p\to h_1(1965)n$ is near an order of magnitude of 10 $μ$b when $p_{\mathrm{Lab}}$ is from 10 to 30 GeV/$c$, and much larger than that of reaction $K^-p\to h_1(1965)Λ$. These predictions can provide some valuable information to search for $X(2100)$ and $h_1(1965)$ in experiments at J-PARC, COMPASS, OKA@U-70 and SPS@CERN.

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Interpretation of the observed $Λ_b(6146)^0$ and $Λ_b(6152)^0$ states as 1$D$ bottom baryons

The measured masses and strong decays of $Λ_b(6146)^0$ and $Λ_b(6152)^0$ required us to decode them as the 1$D$ excited states with $J^P=3/2^+$ and $J^P=5/2^+$, respectively. Under the suggested assignment, the masses and total decay widths of $Λ_b(6146)^0$ and $Λ_b(6152)^0$ can be explained. As a $J^P=3/2^+$ state, the $Λ_b(6146)^0$ should mainly decay into $Σ_b(5815)π$. However, this theoretical result is in contradiction to the measurement since no significant $Λ_b(6146)^0\rightarrowΣ_b(5815)^\pmπ^\mp$ signals were observed by the LHCb. The possible explanations to this difficulty are mentioned. For completeness, we present the prediction of masses and decay widths of other unseen 1$D$ bottom baryons in this work. Our results could provide some important clues for the upcoming experiments.

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Exotic tetraquark states with the $qq\bar{Q}\bar{Q}$ configuration

In this work, we study systematically the mass splittings of the $qq\bar{Q}\bar{Q}$ ($q=u$, $d$, $s$ and $Q=c$, $b$) tetraquark states with the color-magnetic interaction by considering color mixing effects and estimate roughly their masses. We find that the color mixing effect is relatively important for the $J^P=0^+$ states and possible stable tetraquarks exist in the $nn\bar{Q}\bar{Q}$ ($n=u$, $d$) and $ns\bar{Q}\bar{Q}$ systems either with $J=0$ or with $J=1$. Possible decay patterns of the tetraquarks are briefly discussed.

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Constructing new pseudoscalar meson nonets with the observed $X(2100)$, $X(2500)$, and $η(2225)$

Stimulated by the BESIII observation of $X(2100)$, $X(2500)$, and $η(2225)$, we try to pin down new pseudoscalar meson nonets including these states. The analysis of mass spectra and the study of strong decays indicate that $X(2120)$ and $η(2225)$ associated with $π(2070)$ and the predicted kaon $K(2150)$ may form a new pseudoscalar meson nonet. In addition, more experimental data for $X(2100)$ are necessary to determine its structure of nonets. Then, $X(2500)$, $X(2370)$, $π(2360)$, and the predicted kaon $K(2414)$ can be grouped into another new nonet. These assignments to the discussed pseudoscalar states can be further tested in experiment.

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