Angular distribution of \(\Lambda_b^0\to pK^-\ell^+\ell^-\) decays comprising \(\Lambda\) resonances with spin up to \(\leq5/2\)

Abstract

This paper describes the angular distribution of \(\Lambda_b^0\to \Lambda(\to pK^-)\ell^+\ell^-\) decays. A full expression is given for the case of multiple interfering spin-states with spin \(\leq \tfrac{5}{2}\). This distribution is relevant for future measurements of \(\Lambda_b^0\to pK^-\ell^+\ell^-\) decays, where different states cannot easily be separated based on their mass alone. New observables arise when considering spin-\(\tfrac{5}{2}\) 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.