Next-to-leading-order QCD corrections to the yields and polarisations of J/ψ and $ Y $ directly produced in association with a Z boson at the LHC

Abstract

We update the study of the production of direct J/ψ in association with a Z boson at the Next-to-Leading Order (NLO) in α s by evaluating both the yield differential in P T and the J/ψ polarisation in the QCD-based Colour-Singlet Model (CSM). Contrary to an earlier claim, QCD corrections at small and mid P T are small if one assumes that the factorisation and the renormalisation scales are commensurate with the Z boson mass. As it can be anticipated, the t-channel gluon-exchange (t−CGE) topologies start to be dominant only for P T m Z /2. The polarisation pattern is not altered by the QCD corrections. This is thus far the first quarkonium-production process where this is observed in the CSM. Along the same lines, our predictions for direct Υ + Z are also given.

Production ofJ/ψ+ηcversusJ/ψ+J/ψat the LHC: Importance of Rea

“…approximation has been explicitly verified in the inclusive J=c and Ç production [9,10] as well as for J=c þ and Ç þ [15] (It is also worth noting that the NLO ? of J=c þ Z production reproduces quite well the exact NLO result [32], though there is another large energy scale m Z besides P T ). As we show in the next section, the scaling of the NLO ?…”

“…is dominated by novel topologies at 5 s . The only known case where such new topologies create J=c 's with the same polarization as the Born topologies is that of J=c þ Z [32]. Finally, it is interesting to observe that the NLO ?…”

Heavy flavour studies with the ATLAS detector

“…The inner errors are statistical, the outer error bars are statistical and systematic uncertainties added in quadrature. Theory predictions at the LO and NLO level 4,5 are also shown.…”

Quarkonium production in the LHC era: QCD corrections and new observables

“…This is also true for instance when they are produced in association with a photon [14,15]. The sole known case where the quarkonium polarisation is not altered by NLO corrections is when they are produced with a Z-boson [16].…”