Observation of Upsilon(1S) pair production in proton-proton collisions at sqrt(s) = 8 TeV

TL;DR

This paper reports the first observation of Upsilon(1S) pair production in proton-proton collisions at 8 TeV, measuring the cross section and exploring polarization effects using CMS data.

Contribution

It provides the first measurement of Upsilon(1S) pair production cross section at the LHC, including polarization dependence analysis.

Findings

Measured fiducial cross section: 68.8 pb with uncertainties.

Observed polarization effects can alter the cross section by -38% to +36%.

First observation of Upsilon(1S) pairs in proton-proton collisions.

Abstract

Pair production of Upsilon(1S) mesons is observed at the LHC in proton-proton collisions at sqrt(s) = 8 TeV by the CMS experiment in a data sample corresponding to an integrated luminosity of 20.7 inverse femtobarns. Both Upsilon(1S) candidates are fully reconstructed via their decays to mu+ mu-. The fiducial acceptance region is defined by an absolute Upsilon(1S) rapidity smaller than 2.0. The fiducial cross section for the production of Upsilon(1S) pairs, assuming that both mesons decay isotropically, is measured to be 68.8 +/- 12.7 (stat) +/- 7.4 (syst) +/- 2.8 (B) pb, where the third uncertainty comes from the uncertainty in the branching fraction of Upsilon(1S) decays to mu+ mu-. Assuming instead that the Upsilon(1S) mesons are produced with different polarizations leads to variations in the measured cross section in the range from -38% to +36%.