NRQCD: Fundamentals and Applications to Quarkonium Decay and Production

I discuss NRQCD and, in particular, the NRQCD factorization formalism for quarkonium production and decay. I also summarize the current status of the comparison between the predictions of NRQCD factorization and experimental measurements.Comment: 8 pages, 5 eps figures, uses ws-ijmpa.cls, plenary talk presented at the International Conference on QCD and Hadronic Physics, Beijing, China, June, 16--20, 200

Recent Results on Quarkonium Production and Decay

I summarize the current status of the comparison between experiment and the predictions of the NRQCD factorization approach to quarkonium decay and production. I also present the results of some recent calculations and theoretical developments in the NRQCD factorization approach.Comment: 10 pages, uses modified ws-procs9x6.cls (ws-procs9x6-notrim.cls), Plenary talk presented at The 5th International Conference Quark Confinement and the Hadron Spectrum, Gargnano, Italy 10--14 September, 200

Spin correlations and velocity-scaling in color-octet NRQCD matrix elements

We compute spin-dependent decay matrix elements for S-wave charmonium and bottomonium in lattice nonrelativistic quantum chromodynamics (NRQCD). Particular emphasis is placed upon the color-octet matrix elements, since the corresponding production matrix elements are expected to appear in the dominant contributions to the production cross sections at large transverse momenta. We use three slightly different versions of the heavy-quark lattice Green's functions in order to minimize the contributions that scale as powers of the ultraviolet cutoff. The lattice matrix elements that we calculate obey the hierarchy that is suggested by the velocity-scaling rules of NRQCD.Comment: 25 pages, 2 figures, 2 tables, further discussion of effective lattice cutoffs and uncertainties, additional minor revisions, version to be published in Phys. Rev.

Higher-order relativistic corrections to gluon fragmentation into spin-triplet S-wave quarkonium

We compute the relative-order-v^4 contribution to gluon fragmentation into quarkonium in the 3S1 color-singlet channel, using the nonrelativistic QCD (NRQCD) factorization approach. The QCD fragmentation process contains infrared divergences that produce single and double poles in epsilon in 4-2epsilon dimensions. We devise subtractions that isolate the pole contributions, which ultimately are absorbed into long-distance NRQCD matrix elements in the NRQCD matching procedure. The matching procedure involves two-loop renormalizations of the NRQCD operators. The subtractions are integrated over the phase space analytically in 4-2epsilon dimensions, and the remainder is integrated over the phase-space numerically. We find that the order-v^4 contribution is enhanced relative to the order-v^0 contribution. However, the order-v^4 contribution is not important numerically at the current level of precision of quarkonium-hadroproduction phenomenology. We also estimate the contribution to hadroproduction from gluon fragmentation into quarkonium in the 3PJ color-octet channel and find that it is significant in comparison to the complete next-to-leading-order-in-alpha_s contribution in that channel.Comment: 41 pages, 8 figures, 3 tables, minor corrections, version published in JHE

Spin Correlations and Velocity-Scaling in NRQCD Matrix Elements

We compute spin-dependent matrix elements for decays of S-wave quarkonia in lattice NRQCD. They appear to be in approximate agreement with the velocity-scaling rules of NRQCD.Comment: 3 pages, uses aipproc.cls, aipxfm.sty, aip-6s.clo, Talk presented at The VIth International Conference Quark Confinement and the Hadron Spectrum, Villasimius, Sardinia, Italy September 21--25, 200