On the angular distribution of ${\Lambda }_b\to \Lambda (\to N\pi ){\tau }^{+}{\tau }^{-}$ decay

Abstract

We present a full angular distribution of the four body ${\Lambda }_b\to \Lambda (\to N\pi ){\ell }^{+}{\ell }^{-}$ decay where the leptons are massive and the ${\Lambda }_b$ is unpolarized, in an operator basis which includes the Standard Model operators, new vector and axial-vector operators, and scalar and pseudo-scalar operators. The angular coefficients are expressed in terms of transversity amplitudes. We study several ${\Lambda }_b\to \Lambda (\to p\pi ){\tau }^{+}{\tau }^{-}$ observables in the Standard Model and in the presence of the new operators. For our numerical analysis, we use the form factors from lattice QCD calculations.

Comments: accepted by JHEP (charmonium and duality contributions included in this final version)