The semileptonic decay Lambda_b -> Lambda_c + tau(-) + antinu_tau in the covariant confined quark model

TL;DR

This paper investigates the semileptonic decay Lambda_b -> Lambda_c + tau + antinu_tau using the covariant confined quark model, focusing on polarization effects and asymmetries, revealing significant lepton mass impacts.

Contribution

It provides a detailed analysis of Lambda_b semileptonic decay including polarization and asymmetry observables, extending previous meson decay studies with new numerical results.

Findings

Large lepton mass effects in q2-spectra

Significant polarization asymmetries

Predictions for hadron-side asymmetries

Abstract

Recently there has been much interest in the tauonic semileptonic meson decays B -> D + tau + nu_tau and B -> D* + tau + nu_tau where one has found larger rates than what is predicted by the Standard Model. We analyze the corresponding semileptonic baryon decays Lambda_b(0) -> Lambda_c(+) + tau(-) + antinu_tau with particular emphasis on the lepton helicity flip and scalar contributions which vanish for zero lepton masses. We calculate the total rate, differential decay distributions, the longitudinal and transverse polarization of the daughter baryon Lambda_c(+) and the tau-lepton, and the lepton-side forward-backward asymmetries. The nonvanishing polarization of the daughter baryon Lambda_c(+) leads to hadron-side asymmetries in e.g. the decay Lambda_c(+) -> Lambda(0) + pi(+) and azimuthal correlations between the two final state decay planes which we specify. We provide numerical results on these observables using results of the covariant confined quark model. We find large lepton mass effects in the q2-spectra and in the polarization observables.