Measurement of χc1and χc2production with √s = 7 TeV pp collisions at ATLAS

Abstract

The prompt and non-prompt production cross-sections for the χc1and χc2charmonium states are measured in pp collisions at √s = 7TeV with the ATLAS detector at the LHC using 4.5 fb−1of integrated luminosity. The χcstates are reconstructed through the radiative decay χc→ J/ψγ (with J/ψ → μ+μ−) where photons are reconstructed from γ → e+e− conversions. The production rate of the χc2state relative to the χc1state is measured for prompt and non-prompt χcas a function of J/ψ transverse momentum. The prompt χccross-sections are combined with existing measurements of prompt J/ψ production to derive the fraction of prompt J/ψ produced in feed-down from χcdecays. The fractions of χc1and χc2produced in b-hadron decays are also measured.