Abstract
The PHENIX experiment at the Relativistic Heavy Ion Collider has measured the differential cross section, mean transverse momentum, mean transverse momentum squared of inclusive J/ψ, and cross section ratio of ψ(2S) to J/ψ at forward rapidity in p+p collisions at s=510 GeV via the dimuon decay channel. Comparison is made to inclusive J/ψ cross sections measured at s=200 GeV and 2.76–13 TeV. The result is also compared to leading-order nonrelativistic QCD calculations coupled to a color-glass-condensate description of the low-x gluons in the proton at low transverse momentum (pT) and to next-to-leading order nonrelativistic QCD calculations for the rest of the pT range. These calculations overestimate the data at low pT. While consistent with the data within uncertainties above ≈3 GeV/c, the calculations are systematically below the data. The total cross section times the branching ratio is BR dσppJ/ψ/dy(1.2<|y|<2.2,0<pT<10 GeV/c)=54.3±0.5(stat)±5.5(syst) nb.4 MoreReceived 1 January 2020Accepted 19 February 2020DOI:https://doi.org/10.1103/PhysRevD.101.052006Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasLeptonic, semileptonic & radiative decaysParticle productionRelativistic heavy-ion collisionsPhysical SystemsCharmed mesonsMuonsTechniquesHadron collidersParticles & Fields
Highlights
Charmonium states such as J=ψ and ψð2SÞ mesons are bound states of a charm and anticharm quark
At the Relativistic Heavy Ion Collider (RHIC) energies, they are produced mostly from hard scattering of two gluons into a ccpair followed by the evolution of this pair through a hadronization process to form a physical charmonium
NBMBBC 1⁄4 3.02 × 1012 is the number of minimum bias (MB) events, and εBBC 1⁄4 0.91 Æ 0.04 is the efficiency of the MB trigger for events containing a hard scattering [22p].ffiffiσBBC is the PHENIX beam-beam counter (BBC) cross section, 32.5 Æ 3.2 mb at s 1⁄4 510 GeV, which is determined from the van der Meer scan technique [23]
Summary
Charmonium states such as J=ψ and ψð2SÞ mesons are bound states of a charm and anticharm quark (cc). Transverse momentum (pT) and of rapidity (y) at different energies is essential to understanding production mechanisms These measurements over a wide range of pT (down to zero pT) and rapidity allow calculating quantities, such as the mean transverse momentum hpTi, the mean transverse momentum squared hp2Ti, and the pT-integrated cross section dσ=dy. The collision energy dependence of these quantities can put stringent constraints on the different theoretical approaches that are used to describe the hadronic production of J=ψ These approaches include the color-evaporation model [10,11], the color-singlet model [12], and the nonrelativistic quantum chromodynamics formalism (NRQCD) [13]. We present the inclusive J=ψ production cross section and the ratio of ψð2SÞ to J=ψ production cross sections at forward rapidity (1.2 < jyj < 2.2) measpuffisrffie1⁄4d in 510 p þ p collisions GeV These mesons at are center-of-mass measured in the energy dimuon.
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