Measurement of the fraction of Y1S originating from chib1P decays in $pp$ collisions at $sqrt{s} = 7tev$

The production of chib1P mesons in $pp$ collisions at a centre-of-mass energy of $7tev$ is studied using $32invpb$ of data collected with the lhcb detector. The $chib1P$ mesons are reconstructed in the decay mode $chib1P to Y1Sg to mumug$. The fraction of Y1S originating from chib1P decays in the Y1S transverse momentum range $6 < pt^{Y1S} < 15gevc$ and rapidity range $2.0 < y^{Y1S} < 4.5$ is measured to be $(20.7pm 5.7pm 2.1^{+2.7}_{-5.4})%$, where the first uncertainty is statistical, the second is systematic and the last gives the range of the result due to the unknown Y1S and chib1P polarizations.