Study of the dilepton electromagnetic decays of χcJ(1P)

• Published in: The European physical journal. C, Particles and fields Particles and fields, 2019-12, Vol.79 (12)
• Main Authors: Wang, Xuan-He, Jiang, Yue, Wang, Tianhong, Tan, Xiao-Ze, Li, Geng, Wang, Guo-Li
• Format: Article
• Language: English
• Subjects: Astronomy; Astrophysics and Cosmology; Decay; Elementary Particles; Gauge invariance; Hadrons; Heavy Ions; Leptons; Mathematical analysis; Measurement Science and Instrumentation; Nuclear Energy; Nuclear Physics; Physics; Physics and Astronomy; Quantum Field Theories; Quantum Field Theory; Regular Article - Theoretical Physics; String Theory
• ISSN: 1434-6044; 1434-6052
• DOI: 10.1140/epjc/s10052-019-7531-8

In this paper, the dilepton electromagnetic decays χ cJ ( 1 P ) → J / ψ e + e - and χ cJ ( 1 P ) → J ψ μ + μ - , where χ cJ denotes χ c 0 , χ c 1 and χ c 2 , are calculated systematically in the improved Bethe–Salpeter method. The numerical results of decay widths and the invariant mass distributions of the final lepton pairs are given. The comparison is made with the recently measured experimental data of BESIII. It is shown that for the cases including e + e - , the gauge invariance is decisive and should be considered carefully. For the processes of χ cJ ( 1 P ) → J / ψ e + e - , the branching fraction are: B [ χ c 0 ( 1 P ) → J / ψ e + e - ] = 1 . 06 - 0.18 + 0.16 × 10 - 4 , B [ χ c 1 ( 1 P ) → J / ψ e + e - ] = 2 . 88 - 0.53 + 0.50 × 10 - 3 , and B [ χ c 2 ( 1 P ) → J / ψ e + e - ] = 1 . 74 - 0.21 + 0.22 × 10 - 3 . The calculated branching fractions of χ cJ ( 1 P ) → J / ψ μ + μ - channels are: B [ χ c 0 ( 1 P ) → J / ψ μ + μ - ] = 3 . 80 - 0.64 + 0.59 × 10 - 6 , B [ χ c 1 ( 1 P ) → J / ψ μ + μ - ] = 2 . 04 - 0.38 + 0.36 × 10 - 4 , and B [ χ c 2 ( 1 P ) → J / ψ μ + μ - ] = 1 . 66 - 0.19 + 0.19 × 10 - 4 .