Form-factor-independent test of lepton universality in semileptonic heavy meson and baryon decays

Stefan Groote, Mikhail A. Ivanov, Jürgen G. Körner, Valery E. Lyubovitskij, Pietro Santorelli, Chien Thang Tran

Research output: Contribution to journalArticlepeer-review

Abstract

In the semileptonic decays of heavy mesons and baryons, the lepton-mass dependence factors out in the quadratic cos2θ coefficient of the differential cosθ distribution. We call the corresponding normalized coefficient the convexity parameter. This observation opens the path to a test of lepton universality in semileptonic heavy meson and baryon decays that is independent of form-factor effects. By projecting out the quadratic rate coefficient, dividing out the lepton-mass-dependent factor, and restricting the phase space integration to the τ lepton phase space, one can define optimized partial rates which, in the Standard Model, are the same for all three (e,μ,τ) modes in a given semileptonic decay process. We discuss how the identity is spoiled by new physics effects. We discuss semileptonic heavy meson decays such as B¯0→D(∗)+ℓ-ν¯ℓ and Bc-→J/ψ(ηc)ℓ-ν¯ℓ and semileptonic heavy baryon decays such as Λb→Λcℓ-ν¯ℓ for each ℓ=e, μ, τ.

Original languageEnglish
Article number093001
JournalPhysical Review D
Volume103
Issue number9
DOIs
Publication statusPublished - 11 May 2021

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)

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