1,877 research outputs found
Local duality for the -meson width revisited
Local duality estimates for the -meson leptonic width and the spectrum
of radial excitations are updated. New perturbative corrections are included in
the analysis that gives good agreement with experimental data on low energy
resonances.Comment: 10 pages, Late
COMPUTATION OF COEFFICIENT FUNCTIONS FOR AN EXPANSION OF PARAPOSITRONIUM DECAY WIDTH USING REDUCE
A kind of asymptotic expansion for calculation of the (para)positronium decay
rate is formulated. The method is completely relativistic and gauge invariant.
The expansion goes over the inverse square of relative momentum of two
photons in Euclidean region and the actual width is determined at ,
being the electron mass.Comment: Latex fil
On the nonrelativistic dynamics of heavy particles near the production threshold
A solution to the Schrodinger equation for the nonrelativistic Green function
which is used for describing the heavy quark-antiquark pair production near the
threshold in annihilation is presented. A quick comparison with
existing results is given. A choice of the effective mass scale for the
nonrelativistic system with Coulomb interaction is discussed.Comment: 12 pages, late
Heavy quark production near the threshold in QCD
Theoretical results for the cross section of heavy quark production near the
threshold at NNLO of NRQCD are briefly overviewed.Comment: Talk given at 10th Lomonosov conference on Elementary Particle
Physics, August 2001, Moscow, Russia, 9 pages, Late
Renormalization group analysis of the tau-lepton decay within QCD
A technique to sum up the regular corrections appearing under the analytic
continuation from the spacelike momentum region to the timelike one is
proposed. A perturbative part of the inclusive semileptonic decay width of the
tau-lepton in analyzed in detail.Comment: Electronic version of the published paper, latex, 6 page
Determination of the numerical value for the strong coupling constant from tau decays in perturbative QCD
The determination of the numerical value for the strong coupling constant
from tau decays in perturbative QCD is briefly described. Main emphasis is made
on the use of the renormalization scheme invariance of the theory for reducing
uncertainties related to truncation of the series in the strong coupling
constant. The analysis of the convergence of the series is presented and the
possibility of the asymptotic growth at the NNNLO is discussed.Comment: Talk given at 15th International Seminar ``Quarks-2002'', Novgorod
the Great, Russia, June 1-7, 2002, latex, 14 page
Mixing of neutral B mesons and factorization
A brief review of checking the factorization hypothesis for matrix element of
mixing within operator product expansion and QCD sum rules is
given. Both perturbative and power corrections are considered.Comment: LaTeX file, 7 page
Computing non-factorizable pQCD corrections to hadronic B^0 - \bar B^0 mixing matrix element within sum rules technique for three point Green functions
In this talk I report on the results of a recent calculation of the \alpha_s
corrections to a three-point correlation function at the three-loop level in
QCD perturbation theory, which allows one to extract the matrix element of B^0
-\bar B^0 mixing with next-to-leading order accuracy. The evaluation of mixing
parameter at NLO allows for a consistent analysis of B^0 -\bar B^0 mixing since
the coefficient functions of the effective Hamiltonian for this process are
known with the necessary accuracy.Comment: 10 pages, Latex, 4 figures, Q-2004 tal
High order PT calculations for heavy quarks near threshold
Results of analytical calculations for heavy quark systems in higher orders
of perturbation theory are overviewed. I discuss baryons with one finite mass
quark in the next-to-leading order and heavy quark pair production near the
threshold within NRQCD.Comment: 14 pages, latex, 1 figure. Talk given at Research Workshop
``Calculations for Modern and Future Colliders'', JINR, Dubna, Russia, July
9-23, 200
Analytical results for and observables near the threshold up to the next-to-next-to-leading order of NRQCD
We present an analytical description of top-antitop pair production near the
threshold in annihilation and \g\g collisions. A set of basic
observables considered includes the total cross sections, forward-backward
asymmetry and top quark polarization. The threshold effects relevant for the
basic observables are described by three universal functions related to S wave
production, P wave production and S-P interference. These functions are
computed analytically up to the next-to-next-to-leading order of NRQCD. The
total cross section near the threshold is obtained in the
next-to-next-to-leading order in the closed form including the contribution due
to the axial coupling of top quark and mediated by the Z-boson. The effects of
the running of the strong coupling constant and of the finite top quark width
are taken into account analytically for the P wave production and S-P wave
interference.Comment: 46 pages LaTeX, editorial change
- …