Constraint on the branching ratio of Bc−→τν¯ from LEP1 data and consequences for

Abstract

Recently there has been interest in the correlation between R(D * ) and the branching ratio (BR) of B − c → τν in models with a charged scalar H ± . Any enhancement of R(D * ) by H ± alone (in order to agree with current data) also enhances BR(B − c → τν), for which there has been no direct search at hadron colliders. We show that LEP data taken at the Z peak requires BR(B − c → τν) 10%, and this constraint is significantly stronger than the recent constraint BR(B − c → τν) 30% from considering the lifetime of B c . In order to respect this new constraint, any explanation of the R(D) and R(D * ) anomaly in terms of H ± alone would require the future measurements of R(D * ) to be even closer to the Standard Model prediction. A stronger limit on BR(B − c → τν) (or its first measurement) would be obtained if the L3 collaboration used all its data taken at the Z peak. * Electronic address: a.g.akeroyd@soton.ac.uk † Electronic address:

Charged current b→cτν¯τ anomalies in a general W′ boson scenario

“…Furthermore, the polarizations of the τ lepton and D * are also useful observables to potentially distinguish the underlying NP [31,32,44,45]. The potential NP scenarios that could explain the R(D ( * ) ) and R(J/ψ) anomalies, would also affect the branching ratio associated to the leptonic decay B − c → τ −ν τ [121,122], since all of them are generated by the same quark level transition b → cτν τ . In Ref.…”

Implications of new physics in the decays Bc→(J/ψ, ηc)τTran1, Ivanov2, Körner3 et al. 2018Phys. Rev. D844701View full textAdd to dashboardCite

“…(2) are obtained by using experimental data for the ratios of branching fractions R D ¼ 0.407 AE 0.046, R D Ã ¼ 0.304 AE 0.015 [13], and R J=ψ ¼ 0.71 AE 0.25 [3], as well as the requirement BðB c → τνÞ ≤ 10% from the LEP1 data [41]. It should be mentioned that within the SM our calculation yields R D ¼ 0.267, R D Ã ¼ 0.238, and R J=ψ ¼ 0.24.…”

“…In this paper we adopt the second approach by proposing an SM-extended effective Hamiltonian consisting of the full set of the four-fermion operators. Constraints on the corresponding Wilson coefficients are obtained from the experimental data for the ratios R J=ψ and R D ðÃÞ , as well as the LEP1 data, which requires BðB c → τνÞ ≤ 10% [41]. Another useful constraint is provided by using the lifetime of B c as discussed in Ref.…”

Phenomenology of Ξb→Ξcτν decays

“…Calculations of the mean lifetime of the B c meson τ B c ¼ 0.52 þ0.18 −0.12 ps in the SM [17][18][19] suggest that BðB c → τνÞ cannot exceed 5% to comply with the current world average of the B c lifetime. Although this constraint can be relaxed up to about 30%, very recently [20] a more stringent limit of BðB c → τνÞ ≤ 10% was obtained by analyzing the LEP data at the Z peak. The constraint coming from the B c meson decay width is also discussed in detail.…”