在同时考虑π介子和σ介子交换势的情况下，我们对$D^0\bar{D}^{\ast0}$系统进行了动力学计算。$σ$介子交换势是排斥重夸克对称性和数值重要的松散束缚系统。如果我们使用实验的$D^\ast Dπ$耦合常数$g=0.59$和1 GeV附近的合理截止值（这是典型的强子尺度），我们的分析不支持将X（3872）解释为松散束缚的分子态。具有负本征值的$D\bar{D}^\ast$系统的束缚态解仅存在于非常大的耦合常数（实验值的两倍）或大的截止值（$Λ\sim 6$ GeV或$β\sim 6$ GeV $^2$）。相反，可能存在一个松散的S波$B\bar{B}^\ast$分子态。一旦产生，这种分子状态将是相当稳定的，因为其主要衰变模式是通过$B^\ast\to B γ$的辐射衰变。对这些状态的实验研究将是非常有趣的。
英文摘要：
After taking into account both the pion and sigma meson exchange potential, we have performed a dynamical calculation of the $D^0\bar{D}^{\ast0}$ system. The $σ$ meson exchange potential is repulsive from heavy quark symmetry and numerically important for a loosely bound system. Our analysis disfavors the interpretation of X(3872) as a loosely bound molecular state if we use the experimental $D^\ast Dπ$ coupling constant $g=0.59$ and a reasonable cutoff around 1 GeV, which is the typical hadronic scale. Bound state solutions with negative eigenvalues for the $D\bar{D}^\ast$ system exist only with either a very large coupling constant (two times of the experimental value) or a large cutoff ($Λ\sim 6$ GeV or $β\sim 6$ GeV$^2$). In contrast, there probably exists a loosely bound S-wave $B\bar{B}^\ast$ molecular state. Once produced, such a molecular state would be rather stable since its dominant decay mode is the radiative decay through $B^\ast\to B γ$. Experimental search of these states will be very interesting.
On March 26th, 2019, at the Rencontres de Moriond QCD conference, the LHCb Collaboration reported the observation of three new pentaquarks, namely $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$, which are consistent with the loosely bound molecular hidden-charm pentaquark states composed of an S-wave charmed baryon $Σ_c$ and an S-wave anti-charmed meson ($\bar{D}, \bar{D}^*$). In this work, we present a direct calculation by the one-boson-exchange (OBE) model and demonstrate explicitly that the $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$ do correspond to the loosely bound $Σ_c\bar{D}$ with $(I=1/2,J^P=…
We perform a systematical investigation of the possible deuteron-like bound states with configuration $Ξ_{cc}N (\bar{N})$, where $N(\bar{N})$ denotes the nucleon (anti-nucleon), in the framework of the one-boson-exchange-potential model. In the spin-triplet sector we take into account both the ${}^3S_1$ and ${}^3D_1$ channels due to non-vanishing tensor force. There exist several candidates of the loosely bound molecular states for the $Ξ_{cc}N$ and $Ξ_{cc}\bar{N}$ systems, which lie below the threshold of $Λ_cΛ_c$ or $Λ_c{\barΛ}_c$. We also investigate the possible loosely bound states with c…
In 2012, we investigated the possible molecular states composed of two charmed mesons [Phys.Rev. D 88, 114008 (2013), arXiv:1211.5007 [hep-ph](2012)]. The $D^*D$ system with the quantum numbers of $I(J^P)=0(1^+)$ was found to be a good candidate of the loosely bound molecular state. This state is very close to the $D^*D$ threshold with a binding energy around 0.47 MeV. This prediction was confirmed by the new LHCb observation of $T_{cc}^+$ [see Franz Muheim's talk at the European Physical Society conference on high energy physics 2021].
We consider decays of the hidden charm LHCb pentaquarks in the hadrocharmonium and molecular scenarios. In both pictures the LHCb pentaquarks are essentially nonrelativistic bound states. We develop a semirelativistic framework for calculation of the partial decay widths that allows the final particles to be relativistic. Using this approach we calculate the decay widths in the hadrocharmonium and molecular pictures. Molecular hidden charm pentaquarks are constructed as loosely bound states of charmed and anticharmed hadrons. Calculations show that molecular pentaquarks decay predominantly int…
We proposed a unified framework to describe the interactions of the observed $T_{cc}$, $P_c$, and $P_{cs}$ within a quark level interaction in our previous work. In this work, we generalize our framework to the loosely bound hadronic molecules composed of heavy flavor di-hadrons with strangeness. We predict the possible $D^{(*)}D^{(*)}_s$ molecular states in the SU(3) limit with the masses of the $P_c$ states as the inputs. We also investigate the baryon-meson and baryon-baryon systems and consider the SU(3) breaking effect in their flavor wave functions. We generalize our isospin criterion of…
With a quark level interaction, we give a unified description of the loosely bound molecular systems composed of the heavy flavor hadrons $(\bar{D},\bar{D}^*)$, $(Λ_c, Σ_c, Σ_c^*)$, and $(Ξ_c, Ξ_c^\prime,Ξ_c^*)$. Using the $P_c$ states as inputs to fix the interaction strength of light quark-quark pairs, we reproduce the observed $P_{cs}$ and $T_{cc}^+$ states and predict another narrow $T_{cc}^{\prime+}$ state with quantum numbers $[D^*D^*]_{J=1}^{I=0}$. If we require a satisfactory description of the $T_{cc}^+$ and $P_c$ states simultaneously, our framework prefers the assignments of the $P_…
Stimulated by the observations of recent observation of $Ω_c$ as well as former one of $P_c(4380)$ and $P_c(4450)$, we perform a coupled channel analysis of $Ξ_c^*\bar{K}/Ω_cη/Ω_c^*η/Ξ_c\bar{K}^*/Ξ_c'\bar{K}^*/Ω_cω$ systems to search for possible $Ω_c-$like molecular states by using a one-boson-exchange potential. Our results suggest there exists a loosely bound molecular state, a $Ξ_c^*\bar{K}/Ω_cη/Ω_c^*η/Ξ_c\bar{K}^*/Ξ_c'\bar{K}^*/Ω_cω$ with $I(J^P)=0(3/2^-)$, it is mainly composed of the $Ξ_c^*\bar{K}$ system. Two-body strong decay width is also studied, where we find that $Ξ_c'\bar{K}$ is …
We study the $Z_{cs}(3985)$ state recently observed by the BESIII Collaboration in the one-boson-exchange model, assuming that it is a $\bar{D}_s^{(*)}D^{(*)}$ molecule, which has the quark content $c\bar{c}s\bar{q}$ with $q = u$, $d$. It is shown that the one-boson-exchange potential is too weak to generate dynamcally $\bar{D}_s D$, $\bar{D}^*_s D$, and $\bar{D}_sD^*$ states, while for the case of $\bar{D}^*_s D^*$, very loosely bound states are likely, with binding energies of the order of several MeV. We conclude that, the observed $Z_{cs}(3985)$ state, if confirmed by further experiments, …
Mass spectra and electromagnetic characteristics of the $K^{(*)}\bar D^{(*)}$ and $K^{(*)}{D}^{(*)}$ molecular tetraquarks from the coupled-channel dynamics
School of Physical Science and Technology, Lanzhou University（兰州大学物理科学与技术学院）；Lanzhou Center for Theoretical Physics, Key Laboratory of Theoretical Physics of Gansu Province, Key Laboratory of Quantum Theory and Applications of MoE, Gansu Provincial Research Center for Basic Disciplines of Quantum Physics, Lanzhou University（兰州大学理论物理中心、甘肃省理论物理重点实验室、教育部量子理论与应用重点实验室、甘肃省量子物理基础学科研究中心）；MoE Frontiers Science Center for Rare Isotopes, Lanzhou University（兰州大学稀土前沿科学中心）；Research Center for Hadron and CSR Physics, Lanzhou University and Institute of Modern Physics of CAS（兰州大学与中国科学院近代物理研究所强子与CSR物理研究中心）
In this work, we propose a possible assignment of the newly observed $X(2239)$, as well as the $η(2225)$, as a molecular state from the interaction of a baryon $Λ$ and an antibaryon $\barΛ$. With the help of effective Lagrangians, the $Λ\barΛ$ interaction is described within the one-boson-exchange model with $η$, $η'$, $ω$, $ϕ$, and $σ$ exchanges considered. After inserting the potential kernel into the quasipotential Bethe-Salpeter equation, the bound states from the $Λ\barΛ$ interaction can be studied by searching for the pole of the scattering amplitude. Two loosely bound states with spin p…
The question on whether or not weakly bound states should be effectively incorporated in a hadronic representation of the QCD partition function is addressed by analyzing the example of the $X(3872)$, a resonance close to the $D\bar D^*$ threshold which has been suggested as an example of a loosely bound molecule. This can be decided by studying the $D \bar D^*$ scattering phase-shifts in the $J^{PC}=1^{++}$ channel and their contribution to the level density in the continuum, which also gives information on its abundance in a hot medium. In this work, it is shown that, in a purely molecular p…
Inspired by the $T^+_{cc}$ signal discovered by the LHCb Collaboration, we systematically investigate the doubly heavy tetraquark states with the molecule configuration $[Q_1\bar{q}_2][Q_3\bar{q}_4]$ ($Q=c$ and $b$, $q=u$, $d$ and $s$) in a nonrelativistic quark model. The model involves a color screening confinement potential, meson-exchange interactions and one-gluon-exchange interactions. The $T^+_{cc}$ state with $IJ^P=01^+$ is a very loosely bound deuteron-like state with a binding energy around 0.34 MeV and a huge size of 4.32 fm. Both the meson exchange force and the coupled channel eff…
Study on the possible molecular states composed of $Λ_c\bar D^*$, $Σ_c\bar D^*$, $Ξ_c\bar D^*$ and $Ξ_c'\bar D^*$ in the Bethe-Salpeter frame based on the pentaquark states $P_c(4440)$, $P_c(4457)$ and $P_{cs}(4459)$
