153 research outputs found
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
Relativistic Corrections to the Exclusive Decays of C-even Bottomonia into S-wave Charmonium Pairs
Within the nonrelativistic quantum chromodynamics (NRQCD) factorization
formalism, we compute the relativistic corrections to the exclusive decays of
bottomonia with even charge conjugation parity into -wave charmonium pairs
at leading order in the strong coupling constant. Relativistic corrections are
resummed for a class of color-singlet contributions to all orders in the
charm-quark velocity in the charmonium rest frame. Almost every process
that we consider in this work has negative relativistic corrections ranging
from -20 to -35,%. Among the various processes, the relativistic corrections of
the next-to-leading order in to the decay rate for with or 2 are very large. In every case, the
resummation of the relativistic corrections enhances the rate in comparison
with the next-to-leading-order results. We compare our results with available
predictions based on the NRQCD factorization formalism. The NRQCD predictions
are significantly smaller than those based on the light-cone formalism by an or
two orders of magnitudes.Comment: 20 pages, 1 figure. Typos corrected, published versio
- β¦