14 research outputs found
Loop Integrals, R Functions and their Analytic Continuation
To entirely determine the resulting functions of one-loop integrals it is
necessary to find the correct analytic continuation to all relevant kinematical
regions. We argue that this continuation procedure may be performed in a
general and mathematical accurate way by using the function notation
of these integrals. The two- and three-point cases are discussed explicitly in
this manner.Comment: 10 pages (Latex), MZ-TH/93-1
A new Method for Computing One-Loop Integrals
We present a new program package for calculating one-loop Feynman integrals,
based on a new method avoiding Feynman parametrization and the contraction due
to Passarino and Veltman. The package is calculating one-, two- and three-point
functions both algebraically and numerically to all tensor cases. This program
is written as a package for Maple. An additional Mathematica version is planned
later.Comment: 12 pages Late
Semi-Leptonic b-decay at Intermediate Recoil
We compute the O(\alpha_s^2) corrections to the differential rate of the
semileptonic decay b -> clv at the "intermediate recoil" point, where the
c-quark mass and the invariant mass of the leptons are equal. The calculation
is based on an expansion around two opposite limits of the quark masses
m_{b,c}: m_c ~ m_b and m_c << m_b. The former case was previously studied; we
correct and extend that result. The latter case is new. The smooth matching of
both expansions provides a check of both. We clarify the discrepancy between
the recent determinations of the full NNLO QCD correction to the semileptonic b
-> c rate, and its earlier estimate.Comment: 9 pages, 6 figures, Replaced figures, small format and typo
corrections, added appendix and reference
Two-loop QCD corrections to semileptonic b decays at maximal recoil
We present a complete correction to the differential width of
the inclusive semileptonic decay at the kinematical point of
vanishing invariant mass of the leptons, . Together with the recently
computed correction at the upper boundary of the lepton
invariant mass spectrum, this new information permits an estimate of the
effect in the total inclusive semileptonic decay width . We argue that the non-BLM part of the correction
gives at most 1% correction to the inclusive semileptonic decay width . This significantly improves the credibility of extracting
from the inclusive semileptonic decays of the b-hadrons.Comment: 8 pages, revte
Special case of sunset: reduction and epsilon-expansion
We consider two loop sunset diagrams with two mass scales m and M at the
threshold and pseudotreshold that cannot be treated by earlier published
formula. The complete reduction to master integrals is given. The master
integrals are evaluated as series in ratio m/M and in epsilon with the help of
differential equation method. The rules of asymptotic expansion in the case
when q^2 is at the (pseudo)threshold are given.Comment: LaTeX, 13 pages, 1 figur
Second order QCD corrections to inclusive semileptonic b \to Xc l \bar \nu_l decays with massless and massive lepton
We extend previous computations of the second order QCD corrections to
semileptonic b \to c inclusive transitions, to the case where the charged
lepton in the final state is massive. This allows accurate description of b \to
c \tau \bar \nu_\tau decays. We review techniques used in the computation of
O(\alpha_s^2) corrections to inclusive semileptonic b \to c transitions and
present extensive numerical studies of O(\alpha_s^2) QCD corrections to b \to c
l \bar \nu_l decays, for l =e, \tau.Comment: 30 pages, 4 figures, 5 table