Rare baryon decays Lambda_b -> Lambda l+ l- (l=e, mu, tau) and Lambda_b -> Lambda gamma : Differential and total rates, lepton- and hadron-side forward-backward asymmetries

TL;DR

This paper calculates differential decay rates and asymmetries for rare Lambda_b baryon decays into Lambda and lepton pairs or gamma, using a covariant quark model and angular analysis, providing numerical predictions and comparisons.

Contribution

It introduces a detailed angular decay analysis and computes observables for Lambda_b decays using a covariant quark model, offering new numerical results and comparisons.

Findings

Calculated differential decay rates and asymmetries.

Provided numerical predictions for observables.

Compared results with existing literature.

Abstract

Using the covariant constituent quark model previously developed by us we calculate the differential rate and the forward-backward asymmetries on the lepton and hadron side for the rare baryon decays Lambda_b -> Lambda l+ l- (l=e, mu, tau) and Lambda_b -> Lambda gamma. We use helicity methods to write down a three-fold joint angular decay distribution for the cascade decay Lambda_b -> Lambda (-> p pi-) + J_eff (-> l+ l-). Through appropriate angular integrations we obtain expressions for the rates, the lepton-side forward-backward (FB) asymmetry and the polarization of the daughter baryon Lambda leading to a hadron-side forward-backward asymmetry. We present numerical results on these observables using the covariant quark model and compare our results to the results of other calculations that have appeared in the literature.