Measurement of the $\hat{I}{›}_b^0\to J/\ddot{I}ˆ\hat{I}›$ angular distribution and the $\hat{I}{›}_b^0$ polarisation in $pp$ collisions

Abstract

This paper presents an analysis of the $\hat{I}{›}_b^0\to J/\ddot{I}ˆ\hat{I}›$ angular distribution and the transverse production polarisation of $\hat{I}{›}_b^0$ baryons in proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV. The measurements are performed using data corresponding to an integrated luminosity of 4.9 fb${}^{-1}$, collected with the LHCb experiment. The polarisation is determined in a fiducial region of $\hat{I}{›}_b^0$ transverse momentum and pseudorapidity of $1<p_T<20$ GeV$/c$ and $2<\hat{I}\cdot <5$, respectively. The data are consistent with $\hat{I}{›}_b^0$ baryons being produced unpolarised in this region. The parity-violating asymmetry parameter of the $\hat{I}›\to p\ddot{I}{€}^{-}$ decay is also determined from the data and its value is found to be consistent with a recent measurement by the BES\,III collaboration.

All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2020-005.html (LHCb public pages)