Speaker
Description
In this work, we perform a comprehensive phenomenological analysis of the exotic hadronic states $Z_c(3900)$, $Z_c(4020)$, $Z_b(10610)$ and $Z_b(10650)$ within the framework of Heavy Quark Spin Symmetry (HQSS) and its violation. By constructing S-wave contact interactions between elastic ($D\bar{D}^*/D^*\bar{D}^*$ or $B\bar{B}^*/B^*\bar{B}^*$) and inelastic ($J/\psi\pi, h_c\pi$ or $\Upsilon\pi$, $h_b\pi$) channels, we solve the Lippmann-Schwinger equation to obtain physical production amplitudes and perform a global fit to experimental invariant-mass spectra. Our results demonstrate a striking difference between the charm and bottom sectors: HQSS violation is negligible in the bottom system, leading to comparable peak structures for both $Z_b$ states in all hidden-bottom decay channels. In contrast, significant HQSS breaking is required to describe the $Z_c$ system, where the violation is predominantly concentrated in the elastic interactions. This explains the observed selectivity: $Z_c(3900)$ appears prominently only in $J/\psi\pi$, while $Z_c(4020)$ appears only in $h_c\pi$. Regardless of whether HQSS violation is taken into account, both the $Z_b(10610)$ and $Z_b(10650)$ poles can appear near the $B\bar{B}^*$ and $B^*\bar{B}^*$ thresholds, respectively. In the hidden charm sector, however, only the framework that includes HQSS violation can successfully describe the experimental data, leading to a single pole around the $D\bar{D}^*$ threshold, which is identified as the $Z_c(3900)$. Meanwhile, the structure associated with the $Z_c(4020)$ is interpreted as a cusp effect. The robustness of our model is verified against variations of the form factor and cutoff, showing stable results.
| 请选择分会 | 强子物理与味物理 |
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