Measurement of the ratio of prompt χc to J/ψ production in pp collisions at √s=7TeV

Abstract

The prompt production of charmoniumχcandJ/ψstates is studied in proton–proton collisionsat a centre-of-mass energy of√s=7 TeV at the Large Hadron Collider. TheχcandJ/ψmesonsare identified through their decaysχc→J/ψγandJ/ψ→μ+μ−using 36 pb−1of data collectedby the LHCb detector in 2010. The ratio of the prompt production cross-sections forχcandJ/ψ,σ(χc→J/ψγ)/σ(J/ψ), is determined as a function of theJ/ψtransverse momentum in the range2<pJ/ψT<15 GeV/c. The results are in excellent agreement with next-to-leading order non-relativisticexpectations and show a significant discrepancy compared with the colour singlet model prediction atleading order, especially in the lowpJ/ψTregion.