Measurement of the Inclusive Upsilon production cross section in pp collisions at $\sqrts=7$~TeV

The $\Upsilon$ production cross section is measured using $280\pm 31 ~{\rm nb}^{-1} $ of proton-proton collisions at $\sqrt{s} = 7$~TeV, collected with the CMS detector. The observed yield of the $\Upsilon$(1S) reconstructed in the dimuon decay channel is $678\pm 38$. Integrated over the rapidity range $|y| < 2.0$, we find the product of the $\Upsilon$(1S) production cross section and branching fraction to be $\sigma(pp \rightarrow \Upsilon {\rm (1S)} X ) \cdot {\cal B} (\Upsilon{\rm (1S)} \rightarrow \mu^+ \mu^-) = (8.3 \pm 0.5 \pm 0.9 \pm 1.0)$~nb, where the first uncertainty is statistical, the second is associated with the estimation of the integrated luminosity of the data sample, and the third includes the remaining systematic contributions. This cross section value is obtained assuming unpolarized $\Upsilon$(1S) production. The $\Upsilon$(1S) production polarization is unknown. Assuming fully transverse or fully longitudinal polarization leads to changes in the cross section by about 20\%. The $\Upsilon$(1S) differential cross section in transverse momentum is also determined. We also find the ratio $[\sigma(pp \rightarrow \Upsilon {\rm (2S)} X )+\sigma(pp \rightarrow \Upsilon {\rm (3S)} X )]/\sigma(pp \rightarrow \Upsilon {\rm (1S)} X )=0.44 \pm 0.06 \pm 0.07$.