Measurement of the $${\eta _{c}} (1S)$$ production cross-section in $$p $$ $$p $$ collisions at $$\sqrt{s} = 13$$ $$\, \text {TeV}$$

Abstract

Using a data sample corresponding to an integrated luminosity of 2.0 fb −1 , collected by the LHCb experiment, the production of the η c (1S) state in proton-proton collisions at a centre-of-mass energy of √ s = 13 TeV is studied in the rapidity range 2.0 < y < 4.5 and in the transverse momentum range 6.5 < p T < 14.0 GeV. The cross-section for prompt production of η c (1S) mesons relative to that of the J/ψ meson is measured using the p p decay mode and is found to be σ η c (1S) /σ J/ψ = 1.69 ± 0.15 ± 0.10 ± 0.18. The quoted uncertainties are, in order, statistical, systematic and due to uncertainties on the branching fractions of the J/ψ → p p and η c → p p decays. The prompt η c (1S) production cross-section is determined to be σ η c (1S) = 1.26 ± 0.11 ± 0.08 ± 0.14 µb, where the last uncertainty includes that on the J/ψ meson cross-section. The ratio of the branching fractions of b-hadron decays to the η c (1S) and J/ψ states is measured to be B b→η c X /B b→J/ψ X = 0.48 ± 0.03 ± 0.03 ± 0.05, where the last uncertainty is due to those on the branching fractions of the J/ψ → p p and η c → p p decays. The difference between the J/ψ and η c (1S) masses is also determined to be 113.0 ± 0.7 ± 0.1 MeV, which is the most precise single measurement of this quantity to date.

The history of LHCb

“…Huge production cross sections of charm and beauty in high-energy pp collisions in the forward region at LHCb [96][97][98][99][100][101][102][103][104][105][106][107][108][109][110][111][112], together with a good reconstruction efficiency, versatile trigger scheme and an excellent momentum and mass resolution, opens up exciting opportunities for spectroscopy measurements. The employment of LHCb's powerful hadron identification system [34,36,113] enables a substantial reduction in the combinatorial background specific to high-energy hadron-hadron collisions.…”

Heavy flavour production at LHCb

“…Table 1: List of the analyses included in this paper with the datasets and the corresponding integrated luminosity used. Reference 7 TeV 8 TeV 13 TeV [4] ψ(2S) production cross-sections 614 pb −1 -275 pb −1 [5] η c (1S) production cross-section --2.0 f b −1 [6] Ξ ++ cc production --1.7 f b −1 [7] B s and Λ b production fractions --1.67 f b −1 [8] B c production fractions 1.0 f b −1 -1.7 f b −1 [9] Ξ − b production rate 1.0 f b −1 1.0 f b −1 1.6 f b −1 In general the first step can be computed with perturbative QCD, while the hadronization is merely non-perturbative and must be determined using experimental results. For this reason the underlying physics process of heavy quarkonium can probe both the perturbative and non-perturbative regime of QCD.…”

Inclusive production of $J/ψ$, $ψ(2S)$, and $Υ$ states in pNRQCD

“…where the last equality follows from the spin symmetry of the quarkonium wavefunctions, which holds up to corrections of relative order v 2 . For this result to be useful, the cross sections need to be multiplied by the branching fractions into the pp final state that were employed by the LHCb measurements [89,90]. While B ηc(1S)→pp = (1.44 ± 0.14) × 10 −3 is available in ref.…”