Lepton polarization asymmetries for FCNC decays of the $\Lambda_b$ baryon

TL;DR

This paper calculates lepton polarization asymmetries and branching ratios for FCNC decays of the mbda_b baryon, showing these asymmetries are largely model-independent and useful for probing Wilson coefficients.

Contribution

It provides new calculations of polarization asymmetries for mbda_b decays using a constituent quark model, highlighting their insensitivity to form factors and potential for new physics insights.

Findings

Branching ratios align with LHCb measurements.

Lepton polarization asymmetries are insensitive to form factors.

Observables can help extract Wilson coefficients independently.

Abstract

Branching ratios, lepton forward-backward asymmetries, and lepton polarization asymmetries for the flavor-changing neutral current (FCNC) dileptonic decays of the $\Lambda_b$ baryon to the ground state and a number of excited state $\Lambda$ baryons are calculated using form factors extracted using wave functions from a constituent quark model. The SM branching ratios for the transition to the ground state calculated using these quark model form factors are consistent with the recent measurement reported by the LHCb collaboration. It is shown that the lepton polarization asymmetries are largely insensitive to the transition form factors and, therefore, to the effects of QCD in the nonperturbative regime. These observables can therefore provide somewhat model independent ways of extracting various combinations of the Wilson coefficients.