How to understand the underlying structures of X(4140)X(4140), X(4274)X(4274), X(4500)X(4500) and X(4700)X(4700)

We investigate the possible rescattering effects which may contribute to the process $B^+\to J/\psi\phi K^+$. It is shown that the $D_{s}^{*+}D_{s}^-$ rescattering via the open-charmed meson loops, and $\psi^\prime \phi$ rescattering via the $\psi^\prime K_1$ loops may simulate the structures of $X(4140)$ and $X(4700)$, respectively. However, if the quantum numbers of $X(4274)$ ($X(4500)$) are $1^{++}$ ($0^{++}$), it is hard to to ascribe the observation of $X(4274)$ and $X(4500)$ to the $P$-wave threshold rescattering effects, which implies that $X(4274)$ and $X(4500)$ could be genuine resonances. We also suggest that $X(4274)$ may be the conventional orbitally excited state $\chi_{c1}(3P)$.Comment: 14 pages, 5 figures, 1 tabl

Investigating possible decay modes of Y(4260)Y(4260) under the D1(2420)Dˉ+c.cD_1(2420)\bar D +c.c molecular state ansatz

By assuming that $Y(4260)$ is a $D_1\bar D$ molecular state, we investigate some hidden-charm and charmed pair decay channels of $Y(4260)$ via intermediate $D_1\bar D$ meson loops with an effective Lagrangian approach. Through investigating the $\alpha$-dependence of branching ratios and ratios between different decay channels, we show that the intermediate $D_1 \bar D$ meson loops are crucial for driving these transitions of $Y(4260)$ studied here. The coupled channel effects turn out to be more important in $Y(4260) \to D^{*}\bar{D}^{*}$, which can be tested in the future experiments.Comment: 8 pages, 6 figures; The width effects of Y(4260) considered; Revised version accepted by Phys. Rev.

Understanding the newly observed heavy pentaquark candidates

We find that several thresholds can contribute to the enhancements of the newly observed heavy pentaquark candidates $P_c^+(4380)$ and $P_c^+(4450)$ via the anomalous triangle singularity (ATS) transitions in the specific kinematics of $\Lambda_b\to J/\psi K^- p$. Apart from the observed two peaks we find that another peaks around 4.5 GeV can also be produced by the ATS. We also show that the $\Sigma_c^{(*)}$ can be produced at leading order in $\Lambda_b$ decay. This process is different from the triangle diagram and its threshold enhancement only appears as CUSP effects if there is no pole structure or the ATS involved. The threshold interaction associated with the presence of the ATS turns out to be a general phenomenon and plays a crucial role in the understanding of candidates for exotic states.Comment: 9 pages, 6 figures, 4 tables; published version in PL

Searching for observable effects induced by anomalous triangle singularities

We investigate the anomalous triangle singularity (ATS) and its possible manifestations in various processes. We show that the ATS should have important impact on our understanding of the nature of some newly observed threshold states. Discussions on how to distinguish the ATS phenomena from genuine dynamic pole structures are presented.Comment: 13 pages, 5 figures, 1 table, version to appear in Phys. Lett.