Extra gauge bosons and lepton flavor universality violation in ϒ and B meson decays

• Published in: Physical review. D 2021-04, Vol.103 (7), p.1, Article 073003
• Main Authors: García-Duque, Cristian H., Muñoz, J. H., Quintero, Néstor, Rojas, Eduardo
• Format: Article
• Language: English
• Subjects: Anomalies; Bosons; Flavor (particle physics); Large Hadron Collider; Leptons; Matter & antimatter; Particle decay; Standard model (particle physics)
• ISSN: 2470-0010; 2470-0029
• DOI: 10.1103/PhysRevD.103.073003

Lepton flavor universality can be tested through the ratio of semileptonic B meson decays and leptonic Υ meson decays, with Υ ≡ Υ ( nS ) ( n = 1 , 2, 3). For the charged-current transitions b → c τ ¯ ν τ , discrepancies between the experiment and the Standard Model (SM) have been observed in recent years by different flavor facilities such as BABAR, Belle, and LHCb. While for the neutral-current transitions bb → ττ, the BABAR experiment reported recently a new measurement of leptonic decay ratio RΥ (3S) = BR ( Υ (3S) → τ+ τ−) / BR ( Υ ( 3 S ) → μ+ μ −), showing an agreement with the SM at the 1.8 σ level. In light of this new BABAR result and regarding the connection between new physics (NP) interpretations to the charged-current b → cτντ anomalies and neutral-current bb → ττ processes, in this study, we revisit the NP consequences of this measurement within a simplified model with extra massive gauge bosons that coupled predominantly to left-handed leptons of the third generation. We show that the BABAR measurement of RΥ (3S) cannot easily be accommodated (within its experimental 1σ range) together with the other b → cτντ data, hinting toward a new anomalous observable.