300 research outputs found
Quarkonium Polarization in the NRQCD Factorization Framework
The NRQCD factorization approach for calculating inclusive production of
heavy quarkonium gives unambiguous predictions for the polarization of
quarkonium states. The factorization formula for polarized states can be
obtained by using the threshold expansion method to calculate the
short-distance coefficients and then using symmetries of NRQD to reduce the
NRQCD matrix elements. A particularly dramatic prediction of the NRQCD
factorization framework is that prompt psi's and psi-primes's produced at the
Tevatron should be predominantly transversely polarized at large transverse
momentum.Comment: 11 pages, LaTeX, invited talk presented at the Quarkonium Physics
Workshop, University of Illinois at Chicago, June 199
Next-to-leading Order Calculation of the Color-Octet 3S1 Gluon Fragmentation Function for Heavy Quarkonium
The short-distance coefficients for the color-octet 3S1 term in the
fragmentation function for a gluon to split into heavy quarkonium states is
calculated to order alpha_s^2. The gauge-invariant definition of the
fragmentation function by Collins and Soper is employed. Ultraviolet
divergences are removed using the MS-bar renormalization procedure. The
longitudinal term in the fragmentation function agrees with a previous
calculation by Beneke and Rothstein. The next-to-leading order correction to
the transverse term disagrees with a previous calculation.Comment: 17 pages, 4 figure
Color and Spin in Quarkonium Production
I describe the NRQCD factorization approach to the inclusive production of
heavy quarkonium, contrasting it with the color-singlet and color evaporation
models. These approaches differ dramatically in their assumptions about the
roles played by color and spin in the production process. They also differ
dramatically in their predictions for the production of charmonium at large
transverse momentum.Comment: 17 pages, LATEX with style file sprocl.st
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