Observation of a new Ξ0b state

Abstract

Using a proton-proton collision data sample collected by the LHCb experiment, corresponding to anintegrated luminosity of8.5fb−1, the observation of a new excitedΞ0bresonance decaying to theΞ−bπþfinal state is presented. The state, referred to asΞbð6227Þ0, has a measured mass and naturalwidth ofmðΞbð6227Þ0Þ¼6227:1þ1.4−1.5 0.5MeV andΓðΞbð6227Þ0Þ¼18:6þ5.0−4.1 1.4MeV, wherethe uncertainties are statistical and systematic. The production rate of theΞbð6227Þ0state relative tothat of theΞ−bbaryon in the kinematic region2<η<5andpT<30GeV is measured to befΞbð6227Þ0fΞ−bBðΞbð6227Þ0→Ξ−bπþÞ¼0.045 0.008 0.004;whereBðΞbð6227Þ0→Ξ−bπþÞis the branchingfraction of the decay, andfΞbð6227Þ0andfΞ−brepresent fragmentation fractions. Improved measurements ofthe mass and natural width of the previously observedΞbð6227Þ−state, along with the mass of theΞ−bbaryon, are also reported. Both measurements are significantly more precise than, and consistent with,previously reported values.