1,235 research outputs found
Decay rates of various bottomonium systems
Using the Bodwin--Braaten--Lepage factorization theorem in heavy quarkonium
decay and production processes, we calculated matrix elements associated with
S- and P-wave bottomonium decays via lattice QCD simulation methods. In this
work, we report preliminary results on the operator matching between the
lattice expression and the continuum expression at one loop level.
Phenomenological implications are discussed using these preliminary
matrix elements.Comment: 4 pages, postscript file (gzip compressed, uudecoded), contribution
to Lat'9
New results on inclusive quarkonium decays
I review some recent progress, leading to a substantial reduction in the
number of non-perturbative parameters, in the calculation of inclusive
quarkonium decay widths in the framework of non-relativistic effective field
theories.Comment: 4 pages, 3 figures, to be published in the proceedings of the
XXXVIIth Rencontres de Moriond (QCD and High Energy Hadronic Interactions),
16-23 March 2002, Les Arcs, Franc
Decays rates for S- and P-wave bottomonium
We use the Bodwin-Braaten-Lepage factorization scheme to separate the long-
and short-distance factors that contribute to the decay rates of ,
(S-wave) and , (P-wave). The long distance matrix
elements are calculated on the lattice in the quenched approximation using a
non-relativistic formulation of the quark dynamics.Comment: 3 pages Latex using espcrc2.sty and epsf.sty + 2 postscript figure
Gluon Fragmentation into Quarkonium
The functions of the gluon fragmentation into quarkonium are
calculated to order . With the recent progress in analysing
quarkonium systems in QCD we show explicitly how the socalled divergence in the
limit of the zero-binding energy, which is related to -wave quarkonia, is
treated correctly in the case of fragmentation functions. The obtained
fragmentation functions satisfy explicitly at the order of the
Altarelli-Parisi equation and when they behave as as
expected. Some comments on the previous results are made.Comment: Type-errors in the text and equations are eliminated. Several
sentences are added in Sect.4. The file is compressed and uuencoded (E-Mail
contact [email protected]
Fragmentation, Factorization and Infrared Poles in Heavy Quarkonium Production
We explore the role of soft gluon exchange in heavy quarkonium production at
large transverse momentum. We find uncanceled infrared poles at NNLO that are
not matched by conventional NRQCD matrix elements. We show, however, that gauge
invariance and factorization require that conventional NRQCD production
operators be modified to include nonabelian phases or Wilson lines. With
appropriately modified operators, factorization is restored at NNLO. We also
argue that, in the absence of special cancellations, infrared poles at yet
higher orders may require the inclusion of additional nonlocal operators, not
present in the NRQCD expansion in relative veloctiy.Comment: 10 pages latex, 6 eps figure
NRQCD matrix elements for S-wave bottomonia and Gamma[eta_b(nS) -> gamma gamma] with relativistic corrections
We determine the leading-order nonrelativistic quantum chromodynamics (NRQCD)
matrix element _Upsilon and the ratio _Upsilon, for
Upsilon=Upsilon(nS) with n=1, 2, and 3 by comparing the measured values for
Gamma[Upsilon -> e^+ e^-] with the NRQCD factorization formula in which
relativistic corrections are resummed to all orders in the heavy-quark velocity
v. The values for _Upsilon, which is the ratio of order-v^2 matrix
element to _Upsilon, are new. They can be used for NRQCD predictions
involving Upsilon(nS) and eta_b(nS) with relativistic corrections. As an
application, we predict the two-photon decay rates for the spin-singlet states:
Gamma[eta_b(1S) -> gamma gamma] = 0.512^{+0.096}_{-0.094} keV, Gamma[eta_b(2S)
-> gamma gamma] = 0.235^{+0.043}_{-0.043} keV, and Gamma[eta_b(3S) -> gamma
gamma] = 0.170^{+0.031}_{-0.031} keV.Comment: 11 pages, minor corrections, version published in Phys. Lett.
Heavy quarkonia
Two complementary approaches to the theory of heavy quarkonia are discussed.
The nonrelativistic potential models give amazingly accurate predictions, but
lack a theoretical justification. The expansion in powers of is
theoretically very acceptable, but is not as good in giving numerical
predictions. The importance of combining these two approaches is stressed.Comment: Presented at QCD'96 Montpellier 4-12 June 1996 7 pages, no figures,
Latex fil
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
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