Constraints on Nonrelativistic-QCD Long-Distance Matrix Elements from J/ψ Plus W/Z Production at the LHC

We study the associated production of prompt J/psi mesons and W or Z bosons within the factorization approach of nonrelativistic QCD (NRQCD) at next-to-leading order in as, via intermediate color singlet S-3(1)[1] and P-3(J)[1] and color octet S-1(0)[8], S-3(1)[8], and P-3(J)[8] states. Requiring for our predictions to be compatible with recent ATLAS measurements yields stringent new constraints on charmonium long-distance matrix elements (LDMEs) being nonperturbative, process-independent input parameters. Considering four popular LDME sets fitted to data of single J=. inclusive production, we find that one is marginally compatible with the data, with central predictions typically falling short by a factor of 3, one is unfavored, the factor of shortfall being about 1 order of magnitude, and two violate cross section positivity for direct J/psi + W/Z production. The large rate of prompt J/psi plus W production observed by ATLAS provides strong evidence for the color octet mechanism inherent to NRQCD factorization, the leading color singlet contribution entering only at O(G(F)alpha(boolean AND)(s)), beyond the order considered here.

Automated summary

We study the associated production of prompt J/psi mesons and W or Z bosons using the factorization approach of nonrelativistic QCD (NRQCD) at next-to-leading order. We find new constraints on charmonium long-distance matrix elements (LDMEs) by comparing our predictions with recent ATLAS measurements. The prompt J/psi plus W production observed by ATLAS provides evidence for the color octet mechanism inherent to NRQCD factorization.