Measurement of the fraction of Υ (1S) originating from χb(1P) decays in pp collisions at $ \sqrt{s}=7\,TeV

The production of χ b (1 P ) 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 χ b (1 P ) mesons are reconstructed in the decay mode χ b (1 P ) → Υ (1 S )γ → μ + μ − γ. The fraction of Υ (1 S ) originating from χ b (1 P ) decays in the Υ (1 S ) transverse momentum range 6 < p T Υ (1 S ) < 15 GeV /c and rapidity range 2 . 0 < y Υ (1S) < 4 . 5 is measured to be $ \left( {20.7\pm 5.7\pm 2.1_{-5.4}^{+2.7 }} \right)\% $ , where the first uncertainty is statistical, the second is systematic and the last gives the range of the result due to the unknown Υ (1 S ) and χ b (1 P ) polarizations.