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中国物理学会期刊

三体衰变过程Bh中来自子过程K*(892,1680)→ ′的贡献

Contributions of the subprocesses K*(892, 1680) → ′ for the three-body decays Bh

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  • B介子的众多三体强子衰变过程在检验标准模型和探索新物理方面均发挥着重要作用. 这些衰变过程中来自共振态粒子的尾部效应的贡献长期被理论界和实验家们所忽略, 而近期的研究发现这些贡献是相当重要的. 在本文中, 我们在PQCD方法下, 对准两体衰变过程 B^+ \to \pi^+K^*0\to \pi^+K^0\eta^\prime, B^0 \to \pi^0 K^*0\to \pi^0 K^0\eta^\prime, B^0 \to K^0\barK^*0\to K^0\barK^0\eta^\prime 以及 B_s^0 \to K^-K^*+ \to K^-K^+\eta^\prime 进行研究, 其中 K^* 为共振态 K^*(892,1680), 并且我们重点关注子过程 K^*(892)\to K\eta^\prime 在这些过程中的虚贡献. 这些过程正被 LHCb 及 Belle-II 实验组所关注或测量. 本文的计算结果显示, 这些衰变过程的分支比在 10^-8-10^-7 的量级, 且激发态 K^*(1680) 在相关过程中对 K\eta^\prime 的贡献接近对应过程中 K^*(892) 对同一末态贡献的两倍.本文的研究结果揭示了B介子三体衰变过程中来自K^*(892)\to K\eta^\prime 的虚贡献的奇特性质.本文的研究结果能够帮助人们深入理解B介子三体衰变过程中不同共振态贡献的特性,也有助于人们研究激发态 K^*(1680) 的性质.

    Three-body hadronic B meson decays offer a rich environment for exploring the Standard Model and potential new physics. These decays are regularly interpreted in terms of the contribution of various scalar, vector and tensor resonant states. The investigation of appropriate decay processes will help us to comprehend the properties and substructures of the involved resonances. In relevant decay processes, the contributions from the tail of Breit-Wigner formula for the involved intermediate states have long been neglected in both theoretical and experimental investigations. In this work, we study the quasi-two-body decays B^+ \to \pi^+K^*0\to \pi^+K^0\eta^\prime, B^0 \to \pi^0 K^*0\to \pi^0 K^0\eta^\prime, B^0 \to K^0\barK^*0\to K^0\barK^0\eta^\prime and B_s^0 \to K^-K^*+ \to K^-K^+\eta^\prime within the perturbative QCD (PQCD) approach, where K^* denotes the resonances K^*(892) and K^*(1680). The corresponding three-body decays are currently under investigation by the LHCb and Belle-II experiments. Our analysis specifically focuses on the virtual contributions arising from the subprocess K^*(892)\to K\eta^\prime in these decay channels. The quasi-two-body framework based on PQCD approach has been discussed in detail in our former works. With the help of the effective weak Hamiltonian, the distribution amplitudes \phi_B for the B meson, \phi_h for the bachelor final state h and \phi_R for the resonance R, the decay amplitude \mathcalA for a quasi-two-body B decay expressed as the convolution \mathcalA=\phi_B\otimes H \otimes \phi_h\otimes \phi_R, where the hard kernel H contains only one hard gluon exchange at leading order. And then, Employing the decay amplitudes derived from the relevant Feynman diagrams for the concerned decay modes, we calculate the branching fractions and CP violations within the PQCD approach, the numerical results are found in the following Table. Our results are valuable for the understanding of various resonance contributions in the three-body B decays and are helpful for studying of the properties of the excited state K^*(1680). This work reveal very interesting and unique feature for the virtual contribution from the Breit-Wigner tail of the subprocess K^*(892)\to K\eta^\prime. As shown in the following figure for the differential branching fractions of the B_s^0 \to K^-K^*(892,1680)^+\to K^-K^+\eta' decays, the bump for the curve with K^*(892) is generated by the tail of the Breit-Wigner formula for the intermediate state along with the phase space factor. This feature should not be interpreted as evidence for a new resonant state around 2.0 GeV.

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