Probing new physics in B¯0→D(*)

Abstract

We study the longitudinal, transverse, and normal polarization components of the tau lepton in the decays B0 → D ( * ) τ − ντ and discuss their role in searching for new physics (NP) beyond the standard model (SM). Starting with a model-independent effective Hamiltonian including non-SM four-Fermi operators, we obtain experimental constraints on different NP scenarios and investigate their effects on the polarization observables. In the SM the longitudinal and transverse polarizations of the tau lepton differ substantially from the corresponding zero lepton mass values of P L = −1 and P T = 0. In addition, P L and P T are very sensitive to NP effects. For the transverse polarization this holds true, in particular, for the effective tensor operator in the case of B0 → D * and for the scalar operator in the case of B0 → D. The T -odd normal polarization P N , which is predicted to be negligibly small in the SM, can be very sizable assuming NP complex Wilson coefficients.We also discuss in some detail how the three polarization components of the tau lepton can be measured with the help of its subsequent leptonic and semihadronic decays.

Simultaneous explanation of R(D (∗)) and b→sμ + μ −: the last scalar leptoquarks standing

“…W gauge bosons [11,14,53,54] 3. Leptoquarks [9,10,12,13,15,16,19,20,42,[55][56][57][58][59][60] Models with charged Higgses lead to (too) large effects in the total B c lifetime [61] and, depending on the coupling structure, can also be disfavored by the q 2 distribution [62][63][64]. Interestingly, if the couplings of the charged Higgs are chosen in such a way that they are compatible with the measured q 2 distribution, these models are ruled out by direct searches [65].…”

Lepton polarization asymmetries in rare semi-tauonic $$ b \rightarrow s $$ b → s exclusive decays at FCC-ee

“…In the context of semileptonic charged currents, τ polarization observables have been considered in details in, e.g., [49], and [50] discusses experimental prospects for Belle II. Here we present a proof of principle study of the viability of the complete B → K ( * ) τ + τ − reconstruction at the FCC-ee (in Sect.…”

Implications of new physics in the decays Bc→(J/ψ, ηc)τTran1, Ivanov2, Körner3 et al. 2018Phys. Rev. DSelf Cite834701View full textAdd to dashboardCite

“…9 we show the convexity parameter C Similar to what has been discussed in Refs. [61][62][63], one can use the polarization of the τ in the semileptonic decays B c → J=ψðη c Þτν to probe for NP. The longitudinal (L), transverse (T), and normal (N) polarization components of the τ are defined as…”