The ratio between the B+c → J/ψτ+ντ and B+c → J/ψμ+νμ branching fractions is measured using a data sample of proton-proton collisions collected by CMS at a center-of-mass energy of 13 TeV in the years 2016–2018 and corresponding to an integrated luminosity of 138 fb−1. The J/ψ meson is identified through its J/ψ → μ+μ− decay and the tau lepton is reconstructed in the hadronic three-prong final state. The measured ratio of branching fractions in this tau decay mode, RhadJ/ψ = 1.04+−00..4450, is combined with the previous analysis based on the τ+ → μ+νμν̄τ leptonic decay channel, leading to RJ/ψ = 0.49 ± 0.26. As this result is consistent with the standard model prediction of 0.258 ± 0.004, no evidence of lepton flavor universality violation is found.
Measurement of the ratio of the B c + → J / ψ τ + ν τ and B c + → J / ψ μ + ν μ branching fractions using three-prong τ lepton decays
Abbrescia, M.;Barbieri, M.;Buonsante, M.;Colaleo, A.;D'Anzi, B.;De Palma, M.;Elmetenawee, W.;Louka, M.;Mastrapasqua, V.;My, S.;Nuzzo, S.;Pellecchia, A.;Pompili, A.;Radogna, R.;Stamerra, A.;Troiano, D.;Venditti, R.;Zaza, A.;
2026-01-01
Abstract
The ratio between the B+c → J/ψτ+ντ and B+c → J/ψμ+νμ branching fractions is measured using a data sample of proton-proton collisions collected by CMS at a center-of-mass energy of 13 TeV in the years 2016–2018 and corresponding to an integrated luminosity of 138 fb−1. The J/ψ meson is identified through its J/ψ → μ+μ− decay and the tau lepton is reconstructed in the hadronic three-prong final state. The measured ratio of branching fractions in this tau decay mode, RhadJ/ψ = 1.04+−00..4450, is combined with the previous analysis based on the τ+ → μ+νμν̄τ leptonic decay channel, leading to RJ/ψ = 0.49 ± 0.26. As this result is consistent with the standard model prediction of 0.258 ± 0.004, no evidence of lepton flavor universality violation is found.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
