10649998
Hadronic J/ psi production calculated in the NRQCD factorization formalism.
The NRQCD factorization formalism of Bodwin, Braaten, and Lepage prescribes how to write quarkonium production rates as a sum of products of short-distance coefficients times nonperturbative long-distance NRQCD matrix elements. We present a calculation of the inclusive cross section for hadronic {psi} production within the framework of the factorization formalism. Our method applies to the case in which the helicity of the {psi} is not measured. In addition to the well-known {ital color}-{ital singlet} production mechanisms, there are equally important mechanisms in which the {ital c{bar c}} pair that forms the {ital J}/{psi} is initially produced in a {ital color}-{ital octet} state, in either a {sup 3}{ital S}{sub 1}, {sup 1}{ital S}{sub 0}, {sup 3}{ital P}{sub 0}, or {sup 3}{ital P}{sub 2} angular-momentum configuration. In our presentation, we faithfully follow the {open_quote}{open_quote}matching{close_quote}{close_quote} procedure, thereby shedding light on the NRQCD factorization formalism. We determine the short-distance coefficients appearing in the factorization formula, and we point out how one may systematically include relativistic corrections in these calculations. {copyright} {ital 1996 The American Physical Society.}
14211746
Power counting and effective field theory for charmonium
We hypothesize that the correct power counting for charmonia is in the parameter {Lambda}{sub QCD}/m{sub c}, but is not based purely on dimensional analysis (as is heavy quark effective theory). This power counting leads to predictions which differ from those resulting from the usual velocity power counting rules of non-relativistic QCD (NRQCD). In particular, we show that while {Lambda}{sub QCD}/m{sub c} power counting preserves the empirically verified predictions of spin symmetry in decays, it also leads to new predictions which include a hierarchy between spin singlet and triplet octet matrix elements in the J/{psi} system, a quenching of the net polarization in production at large transverse momentum, and no end point enhancement in radiative decays. We discuss explicit tests which can differentiate between the traditional and new theories of NRQCD.
118168769
The N N scattering 3S1 - 3D1 mixing angle at NNLO
The 3S1-3D1 mixing angle for nucleon-nucleon scattering, epsilon_1, is calculated to next-to-next-to-leading order in an effective field theory with perturbative pions. Without pions, the low energy theory fits the observed epsilon_1 well for momenta less than $\sim 50$ MeV. Including pions perturbatively significantly improves the agreement with data for momenta up to $\sim 150$ MeV with one less parameter. Furthermore, for these momenta the accuracy of our calculation is similar to an effective field theory calculation in which the pion is treated non-perturbatively. This gives phenomenological support for a perturbative treatment of pions in low energy two-nucleon processes. We explain why it is necessary to perform spin and isospin traces in d dimensions when regulating divergences with dimensional regularization in higher partial wave amplitudes.
118822207
NRQCD Prediction for the Polarization of the J/psi Produced from b-decay
Presented at the Meeting of the Division of Particles and Fields, August 1996, in Minneapolis. The work presented here is based upon a recent paper (hep-ph/9608413) done in collaboration with Oscar F. Hernandez, Ivan Maksymyk, and Helene Nadeau. The NRQCD predictions for the polarization of the J/psi produced in b->J/psi+X, as well as the helicity-summed production rate are presented.
117895382
Exclusive Radiative Decays of Upsilon in SCET
We study exclusive radiative decays of the $\Upsilon$ using soft-collinear effective theory and non-relativistic QCD. In contrast to inclusive radiative decays at the endpoint we find that color-octet contributions are power suppressed in exclusive decays, and can safely be neglected, greatly simplifying the analysis. We determine the complete set of Lorentz structures that can appear in the SCET Wilson coefficients and match onto them using results from a previous calculation. We run these coefficients from the scale $\mups$ to the scale $\Lambda \sim 1 \textrm{GeV}$, thereby summing large logarithms. Finally we use our results to predict the ratio of branching fractions $B(\Upsilon \to \gamma f_2)/B(J/\psi \to \gamma f_2)$, $B(J/\psi \to \gamma f_2)/B(\psi' \to \gamma f_2)$, and the partial rate for $\Upsilon \to \gamma \pi \pi$.
120287775
Extending theSTUFormalism for Electroweak Oblique Corrections to the Case of Light New Physics
Abstract The STU formalism, which parametrizes oblique electroweak corrections due to heavy new physics, has recently been extended to the case of light new physics. In principle, this extended formalism, which involves the six parameters STUVWX , must be used if loop contributions to the oblique corrections entail light new particles with masses in the range ∼ M Z or less. Applying classical equations of motion to manipulate the effective lagrangian, we present here a thorough introductory discussion of the STUVWX formalism, elucidating such subtleties as the connection between S − X and the star formalism of Kennedy and Lynn, the connection between S − X , and the e parameters of Altarelli and Barbieri, and the loss of definite symmetry properties which S and U undergo as the STU parameter set is extended to the case of light new physics. This paper provides a significantly more detailed, expanded, and pedagogic presentation than previous expositions of the STUVWX parameters.
10884562
Creutz ratios from color-truncated lattice configurations.
We investigate whether information about Creutz ratios is encoded, separately, in each gluon color component of numerically generated lattice configurations. Working in SU(2) lattice gauge theory in the Landau gauge, we set two of the three gluon color components to zero, and compensate for the loss of two-thirds of the fluctuation by simply rescaling the remaining component by a factor of {radical}3 . Creutz ratios are then computed with this ``Abelianized`` configuration. We find that the Creutz ratios of loops constructed from Abelianized links converge to the usual Creutz ratios in the scaling regime.