Angular distribution of ${\Lambda }_b^0\to p{K}^{-}{\ell }^{+}{\ell }^{-}$ decays comprising $\Lambda$ resonances with spin up to $\le 5/2$

Abstract

This paper describes the angular distribution of ${\Lambda }_b^0\to \Lambda (\to p{K}^{-}){\ell }^{+}{\ell }^{-}$ decays. A full expression is given for the case of multiple interfering spin-states with spin $\le \frac{5}{2}$. This distribution is relevant for future measurements of ${\Lambda }_b^0\to p{K}^{-}{\ell }^{+}{\ell }^{-}$ decays, where different states cannot easily be separated based on their mass alone. New observables arise when considering spin-$\frac{5}{2}$ states as well as interference between states. An exploration of their behaviour for a variety of beyond the Standard Model scenarios shows that some of these observables exhibit interesting sensitivity to the Wilson coefficients involved in $b\to s{\ell }^{+}{\ell }^{-}$ transitions. Others are insensitive to the Wilson coefficients and can be used to verify the description of ${\Lambda }_b^0\to \Lambda$ form-factors. A basis of weighting functions that can be used to determine all of the angular observables described in this paper in a moment analysis of the experimental data is also provided.

Comments: Final version of the paper including comments during journal review