Angular moments of the decay $\Lambda_b^0 \rightarrow \Lambda \mu^{+} \mu^{-}$ at low hadronic recoil

TL;DR

This paper presents the first measurement of the full set of angular observables in the decay b1_b^0 b1 b1^+ b1^- at low hadronic recoil, using LHCb data, and finds results consistent with the Standard Model.

Contribution

It provides the first complete measurement of all angular observables in b1_b^0 b1 b1^+ b1^- decay at low recoil, using moment analysis on LHCb data.

Findings

Measured forward-backward asymmetries consistent with Standard Model

First full basis of angular observables determined in this decay

Results support Standard Model predictions at low hadronic recoil

Abstract

An analysis of the angular distribution of the decay $\Lambda_b^0 \rightarrow \Lambda \mu^{+} \mu^{-}$ is presented, using data collected with the LHCb detector between 2011 and 2016 and corresponding to an integrated luminosity of approximately $5\,fb^{-1}$. Angular observables are determined using a moment analysis of the angular distribution at low hadronic recoil, corresponding to the dimuon invariant mass squared range $15 < q^{2} < 20\, GeV^2/c^4$. The full basis of observables is measured for the first time. The lepton-side, hadron-side and combined forward-backward asymmetries of the decay are determined to be \begin{align} A_{FB}^{l} & = -0.39 \pm 0.04\,\rm{stat} \pm 0.01\, \rm{syst}, \nonumber\\ A_{FB}^{h} & = -0.30 \pm 0.05\,\rm{stat} \pm 0.02\, \rm{syst}, \nonumber\\ A_{FB}^{lh} & = +0.25 \pm 0.04\,\rm{stat} \pm 0.01\, \rm{syst}. \nonumber \end{align} The measurements are consistent with Standard Model predictions.