Measurement of the Y(nS) polarizations in pp collisions at √s=7 and 8 TeV

Abstract

The polarization of the Y(1S), Y(2S) and Y(3S) mesons, produced in pp collisions at centre-of-mass energies s=7 and 8 TeV, is measured using data samples collected by the LHCb experiment, corresponding to integrated luminosities of 1 and 2 fb−1, respectively. The measurements are performed in three polarization frames, using Y → μμ decays in the kinematic region of the transverse momentum pTΥ < 30 GeV/c and rapidity 2.2 < yY < 4.5. No large polarization is observed.