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/ψ mesons and W or Z bosons within the factorization approach of nonrelativistic QCD (NRQCD) at next-to-leading order in α_{s}, via intermediate color singlet ^{3}S_{1}^{[1]} and ^{3}P_{J}^{[1]} and color octet ^{1}S_{0}^{[8]}, ^{3}S_{1}^{[8]}, and ^{3}P_{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/ψ 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/ψ+W/Z production.

Deciphering the X(3872) via its Polarization in Prompt Production at the CERN LHC.

Based on the hypothesis that the X(3872) exotic hadron is a mixture of χ_{c1}(2P) and other states and that its prompt hadroproduction predominately proceeds via its χ_{c1}(2P) component, we calculate the prompt-X(3872) polarization at the CERN LHC through next-to-leading order in α_{s} within the factorization formalism of nonrelativistic QCD, including both the color-singlet ^{3}P_{1}^{[1]} and color-octet ^{3}S_{1}^{[8]} cc[over ¯] Fock states. We also consider the polarization of the J/ψ produced by the subsequent X(3872) decay. We predict that, under ATLAS, CMS, and LHCb experimental conditions, the X(3872) is largely longitudinally polarized, while the J/ψ is largely transversely polarized.

Top Quark Mass Calibration for Monte Carlo Event Generators.

The most precise top quark mass measurements use kinematic reconstruction methods, determining the top mass parameter of a Monte Carlo event generator m_{t}^{MC}. Because of hadronization and parton-shower dynamics, relating m_{t}^{MC} to a field theory mass is difficult. We present a calibration procedure to determine this relation using hadron level QCD predictions for observables with kinematic mass sensitivity.

η(c) production at the LHC challenges nonrelativistic QCD factorization.

We analyze the first measurement of η_{c} production, performed by the LHCb Collaboration, in the nonrelativistic QCD (NRQCD) factorization framework at next-to-leading order (NLO) in the strong-coupling constant α_{s} and the relative velocity v of the bound quarks including the feeddown from h_{c} mesons. Converting the long-distance matrix elements extracted by various groups from J/ψ yield and polarization data to the η_{c} case using heavy-quark spin symmetry, we find that the resulting NLO NRQCD predictions greatly overshoot the LHCb data, while the color-singlet model provides an excellent description.

J/ψ polarization at the Tevatron and the LHC: nonrelativistic-QCD factorization at the crossroads.

We study the polarization observables of J/ψ hadroproduction at next-to-leading order within the factorization formalism of nonrelativistic quantum chromodynamics. We complete the present knowledge of the relativistic corrections by also providing the contribution due to the intermediate (3)P(J)([8]) color-octet states at this order, which turns out to be quite significant. Exploiting the color-octet long-distance matrix elements previously extracted through a global fit to experimental data of unpolarized J/ψ production, we provide theoretical predictions in the helicity and Collins-Soper frames and compare them with data taken by CDF at Fermilab Tevatron I and II and by ALICE at CERN LHC.

Probing nonrelativistic QCD factorization in polarized J/ψ photoproduction at next-to-leading order.

We analyze the polarization observables of J/ψ photoproduction at next-to-leading order within the factorization formalism of nonrelativistic quantum chromodynamics (NRQCD). This is a complete next-to-leading-order study of heavy-quarkonium polarization including the full relativistic corrections due to the intermediate (1)S(0)([8]), (3)S(1)([8]), and (3)P(J)([8]) color-octet states closing a gap in the worldwide endeavor to test NRQCD factorization at the quantum level. We present theoretical predictions in the helicity, target, and Collins-Soper frames of DESY HERA, evaluated using the color-octet long-distance matrix elements previously extracted through a global fit to experimental data of unpolarized J/ψ production, and confront them with recent measurements by the H1 and ZEUS Collaborations.