Measurement of the fraction of Υ (1S) originating from χb (1P) decays in pp collisions at√s= 7 TeV

Abstract

The production of χb(1P ) mesons in pp collisions at a centre-of-mass energy of 7 TeV is studied using 32 pb−1 of data collected with the LHCb detector. The χb(1P ) mesons are reconstructed in the decay mode χ b (1P ) → Υ (1S)γ → μ + μ −γ. The fraction of Υ (1S) originating from χb(1P ) decays in the Υ (1S) transverse momentum range 6 < pT Υ (1S) < 15 GeV/c and rapidity range 2.0 < y Υ (1S) < 4.5 is measured to be (20.7±5.7±2.1+2.7−5.4)%, where the first uncertainty is statistical, the second is systematic and the last gives the range of the result due to the unknown Υ (1S) and χb(1P) polarizations.