论文标题
在沉重的夸克腐烂中，重夸克旋转对称性破裂的出现
On the emergence of heavy quark spin symmetry breaking in heavy quarkonium decays
论文作者
论文摘要
重夸克旋转对称性（HQSS）意味着，在带有旋转$ S $的重夸克的直接衰减中，只能产生较低的重型Quarkonia，具有相同的自旋$ S $。但是，如果多夸克中间状态参与衰减链，可以克服该选择规则，预计将在$ b $ quark行业中运作良好，从而可以过渡到最终国家的重型Quarkonia，并具有不同的旋转$ s^{\ prime} $。特别是，测得的衰局$υ（10860）\toπz_b^{（\ prime）} \toππυ（ns）$ $（n = 1,2,3）$和$υ（10860）\toπz_b^{（\ prime）} \ toπz_b^{（\ prime）} \ toπh_b（$）通常，通过同时存在$ s_ {b \ bar {b}} = 0 $和$ s_ {b \ bar {b}} = 1 $组件在$ z_b $相等股份的波函数中的1 $组件。同时，对于$ππh_b$最终状态，$ z_b $ $ z_b'$的贡献之间的破坏性干扰使信号在严格的HQSS限制下杀死了零。在本文中，我们讨论了如何通过$ z_b^{（\ prime）} $状态的狭窄来平衡违规，以便在物理情况下，允许平等的过渡强度到具有不同重型夸克旋转的最终状态，以及在质量相互作用的结果是如何恢复量表时，当量表与量表相互作用时，当量表变得不合时宜时，它会变得不合时宜。此外，我们证明了如何获得$ππh_b$和$ππυ$的类似分支分数，以及如何通过对最终状态的$ππ/ k \ bar k $相互作用的分散方法来调和上述HQSS的破裂，并与两个最终状态的低端chiral Dynesics相匹配。
Heavy-quark spin symmetry (HQSS) implies that in the direct decay of a heavy quarkonium with spin $S$, only lower lying heavy quarkonia with the same spin $S$ can be produced. However, this selection rule, expected to work very well in the $b$-quark sector, can be overcome if multiquark intermediate states are involved in the decay chain, allowing for transitions to the final-state heavy quarkonia with a different spin $S^{\prime}$. In particular, the measured decays $Υ(10860)\to πZ_b^{(\prime)} \to ππΥ(nS)$ $(n=1,2,3)$ and $Υ(10860)\to πZ_b^{(\prime)} \to ππh_b(mP)$ ($m=1,2$) appear to have nearly equal strengths which is conventionally explained by a simultaneous presence of both $S_{b\bar{b}}=0$ and $S_{b\bar{b}}=1$ components in the wave functions of the $Z_b$'s in equal shares. Meanwhile, the destructive interference between the contributions of the $Z_b$ and $Z_b'$ to the decay amplitude for a $ππh_b$ final state kills the signal to zero in the strict HQSS limit. In this paper, we discuss how the HQSS violation needs to be balanced by the narrowness of the $Z_b^{(\prime)}$ states in the physical case, to allow for equal transition strengths into final states with different total heavy quark spins, and how spin symmetry is restored as a result of a subtle interplay of the scales involved, when the mass of a heavy quark becomes infinite. Moreover, we demonstrate how similar branching fractions of the decays into $ππh_b$ and $ππΥ$ can be obtained and how the mentioned HQSS breaking can be reconciled with the dispersive approach to the $ππ/ K\bar K$ interaction in the final state and matched with the low-energy chiral dynamics in both final states.
