Measurement of the associated γ+μ^± production cross section in pp̄ collisions at √s=1.8 TeV

Abstract The cross-section of associated J/ψ-ψ(2S) production in proton-proton collisions at a centre-of-mass energy of $$\sqrt{s}$$ s = 13 TeV is measured using a data sample corresponding to an integrated luminosity of 4.2 fb−1, collected by the LHCb experiment. The measurement is performed for both J/ψ and ψ(2S) mesons having transverse momentum pT&lt; 14 GeV/c and rapidity 2.0 &lt; y &lt; 4.5, assuming negligible polarisation of the J/ψ and ψ(2S) mesons. The production cross-section is measured to be 4.5 ± 0.7 ± 0.3 nb, where the first uncertainty is statistical and the second systematic. The differential cross-sections are measured as functions of several kinematic variables of the J/ψ-ψ(2S) candidates. The results are combined with a measurement of J/ψ-J/ψ production, giving a cross-section ratio between J/ψ-ψ(2S) and J/ψ-J/ψ production of 0.274 ± 0.044 ± 0.008, where the first uncertainty is statistical and the second systematic.</jats:p

Measurement of the associated gamma+mu(+/-) production cross section in p(p)over-bar collisions at root s=1.8 TeV

We present the first measurement of associated direct photon+muon production in hadronic collisions, from a sample of 1.8 TeV collisions recorded with the Collider Detector at Fermilab. Quantum chromodynamics (QCD) predicts that these events are primarily from the Compton scattering process cg-->c gamma, with the final state charm quark producing a muon. Hence this measurement is sensitive to the charm quark content of the proton. The measured cross section of 29+/-9 pb is compared to a leading-order QCD parton shower model as well as a next-to-leading-order QCD calculation. [S0556-2821(99)07121-0]

Measurement of the associated gamma+mu(+/-) production cross section in p(p)over-bar collisions at root s=1.8 TeV

We present the first measurement of associated direct photon+muon production in hadronic collisions, from a sample of 1.8 TeV pp collisions recorded with the Collider Detector at Fermilab. Quantum chromodynamics (QCD) predicts that these events are primarily from the Compton scattering process cg→cγ, with the final state charm quark producing a muon. Hence this measurement is sensitive to the charm quark content of the proton. The measured cross section of 29±9 pb is compared to a leading-order QCD parton shower model as well as a next-to-leading-order QCD calculation. ©1999 The American Physical Society