Complete next-to-leading order calculation of theJ/ψandψ′production at hadron colliders

Abstract

A complete next-to-leading order (NLO) calculation in αs for the J/ψ and ψ ′ prompt production at the Tevatron, LHC, and RHIC in nonrelativistic QCD is presented. We argue that the nextto-next-to-leading order (NNLO) color-singlet contribution may not be so important as to resolve the large discrepancy between theory and experiment in J/ψ large pT production cross sections. Therefore, a complete NLO calculation, including both color-singlet and color-octet contribution, is necessary and essential to give a good description for J/ψ and ψ ′ production. We also study the methods to fit the long-distance matrix elements using either two linear combined matrix elements or three matrix elements, and find these two methods can give consistent results. Compared with the measurements at the LHC and RHIC for prompt J/ψ and ψ ′ production, our predictions are found to agree with all data. In particular, the recently released large pT data (up to 60-70 GeV) at the LHC are in good agreement with our predictions. Our results imply that the universality of coloroctet matrix elements holds approximately in charmonium hadroproduction, when one uses fixed order perturbative calculation to describe data (the data in small pT region are not included). Our work may provide a new test for the universality of color-octet matrix elements, and the color-octet mechanism in general.

Quarkonia production at the STAR detector

“…The CEM is able to describe the data well for the entire range of transverse momentum, however it does not include contributions from B decay. The data are also compared to the Non-Relativistic QCD (NRQCD), nextto-leading order (NLO) Color Singlet and Color Octet (CS+CO) [17] model for prompt and direct J/ψ production, which agrees with the data well at high p T , but does not provide a prediction at low p T . Also shown are the next-to-next-to-leading order (NNLO*) Color Singlet (CS) [18] model for direct J/ψ production in p+p collisions.…”

Study of color-octet matrix elements through $$J/\psi $$ J / ψ production in $$e^{+}e^{-}$$

“…Chao et al fit to the J/ψ yield production and polarization from CDF measurements. Their calculations suggest the unpolarized data could be understood by assuming that the contributions from the 3 S 8 1 and 3 P 8 0 channels cancel or the 1 S 8 0 channel dominate the cross sections in comparison with other channels [6,7,11]. Meanwhile, η c production at the LHC could be understood in the same theoretical framework [12].…”

“…The surplus production of J/ψ and ψ in the large transverse momentum region at the Tevatron and the LHC seems to be powerful evidence in favor of NRQCD [2][3][4][5]. Furthermore, the complete next-to-leading order (NLO) corrections (including the contributions from the color-octet and color-singlet channels) were introduced and theoretical predictions with an identical set of long distance matrix elements (LDMEs) were almost compatible with all the J/ψ yield data at hadron colliders [6][7][8][9]. Additionally, χ c production at hadron colliders was proved to be a successful case for the NLO NRQCD calculations [10].…”

Sivers effect in inelastic J/ψ photoproduction in ep↑ collision in color octet model

“…The heavy quark pair may be produced in CO state which then form the CS quarkonium by emitting a soft gluon. NRQCD has been successful to explain the J=ψ hadroproduction at Tevatron [37,38], also data from J=ψ photoproducton at HERA [39][40][41][42] suggests substantial contribution from CO states [43][44][45][46][47][48]. In the single-spin asymmetry (SSA) in ep collision, when the J=ψ is produced in the CS state, the two final state interactions with quark and antiquark lines cancel each other, and the final state interaction with unobserved particles cancel between diagrams having different cuts.…”