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

We present a full angular distribution of the four body ${\mathrm{\Lambda }}_b\to \mathrm{\Lambda }(\to N\pi ){\mathrm{\ell }}^{+}{\mathrm{\ell }}^{-}$ decay where the leptons are massive and the ${\mathrm{\Lambda }}_b$ 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.