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  • Open Access

Form factors for Bc*→ηc+lνl at NLO in QCD

Wei Tao1,*, Ya-Hui Zhao1,†, Li-Ting Wang1,‡, Qin Chang1,§, and Zhen-Jun Xiao2,∥

  • *Contact author: taowei@htu.edu.cn
  • †Contact author: 2402183096@stu.htu.edu.cn
  • ‡Contact author: wanglt@htu.edu.cn
  • §Contact author: changqin@htu.edu.cn
  • ∥Contact author: xiaozhenjun@njnu.edu.cn
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Phys. Rev. D 113, 074004 – Published 2 April, 2026

DOI: https://doi.org/10.1103/zt62-3q94

Abstract

We present the nonrelativistic QCD (NRQCD) calculations at the next-to-leading order (NLO) of αs for Bc*→ηc vector, axial-vector, tensor, and axial-tensor form factors, and obtain complete analytical expressions for the form factors, along with their asymptotic forms in the hierarchical heavy quark limit. Our results show that the NLO corrections are both sizable and well behaved in the low squared transfer momentum (q2) region. Using the NRQCD+lattice+z-series method, we further provide theoretical predictions for Bc*→ηc form factors across the full physical q2 range. Based on these predicted form factors, we finally compute the decay widths and branching fractions for the semileptonic decays Bc*→ηc+lνl.

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Phys. Rev. D 113, 074004– Published 2 April, 2026
  • Received 27 May 2025
  • Accepted 16 March 2026
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