1,544 research outputs found
Polarized Moller Scattering Asymmetries
The utility of polarized electron beams for precision electroweak studies is
described. Parity violating Moller scattering asymmetries in e-e- --> e-e- are
discussed. Effects of electroweak radiative corrections and the running
sin^2(theta_W(Q^2)) are reviewed. The sensitivity of E158 (a fixed target e-e-
experiment at SLAC) and future e-e- collider studies to ``new physics'' is
briefly outlined.Comment: Updated Fig.
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
Threshold expansion for heavy-light systems and flavor off-diagonal current-current correlators
An expansion scheme is developed for Feynman diagrams describing the
production of one massive and one massless particle near the threshold. As an
example application, we compute the correlators of heavy-light quark currents,
(\bar b gamma_mu u) and (\bar b gamma_5 u), through O(alpha_s^2).Comment: 4 pages, revtex
QCD corrections to the t-->H+b decay within the minimal supersymmetric standard model
I present the contribution of gluinos and scalar quarks to the decay rate of
the top quark into a charged Higgs boson and a bottom quark within the minimal
supersymmetric standard model, including the mixing of the scalar partners of
the left- and right-handed top quark. I show that for certain values of the
supersymmetric parameters the standard QCD loop corrections to this decay mode
are diminished or enhanced by several 10 per cent. I show that not only a small
value of 3 GeV for the gluino mass (small mass window) but also much larger
values of several hundreds of GeV's have a non-neglible effect on this decay
rate, against general belief. Last but not least, if the ratio of the vacuum
expectation values of the Higgs bosons are taken in the limit of I
obtain a drastic enhancement due to a \ dependence in the couplings.Comment: UQAM-PHE-94/01, 6 pages, plain tex, 4 figures not included, available
under request via mail or fa
On the QCD corrections to the charged Higgs decay of a heavy quark
Using dimensional regularization for both infrared and ultraviolet
divergences, we confirm that the QCD corrections to the decay width
are equal to those to in the limit of a
large quark mass.Comment: 6 pages, report Alberta Thy-25-9
Unparticle Searches Through Low Energy Parity Violating Asymmetry
In this paper, we study the effects of the unparticles on the
parity-violating asymmetry for the low energy electron-electron scattering,
. Using the data from the E158 experiment at SLAC we
extract the limits on the unparticle coupling , and on the the
energy scale at 95% C.L. for various values of the scaling dimension
Electroweak corrections to decays involving a charged Higgs boson
We present complete one-loop radiative corrections to the decay rate of a top
quark into a charged Higgs boson and a bottom quark, and for the decay of a
charged Higgs boson into leptons. The results are discussed in the framework of
the two Higgs boson extension of the Standard Model suggested by supersymmetry.
The effect of electroweak corrections after exclusion of universal corrections
is found to decrease the partial width of the top quark typically by
5%.Comment: 16 pages plus 11 figures available from the author upon request,
latex, Alberta Thy-29-9
Semileptonic b --> u decays: lepton invariant mass spectrum
We compute O(alpha_s^2) QCD corrections to the lepton invariant mass spectrum
in the decay b --> u l nu_l, relevant for the determination of the CKM matrix
element |V_{ub}|. Our method can also be used to evaluate moments of the lepton
energy distribution with an O(alpha_s^2) accuracy. The abelian part of our
result gives the neutrino invariant mass spectrum in the muon decay and, upon
integration, the O(alpha^2) correction to the muon lifetime.Comment: 5 pages, revte
Semileptonic decays in the limit of a heavy daughter quark
The rate of the semileptonic decay b to c l v is calculated with order
alphas^2 accuracy, as an expansion around the limit of equal masses of the b
and c quarks. Recent results obtained around the limit of the c-quark much
lighter than b are confirmed. Details of the new expansion method are
described.Comment: 7 pages, 5 figure
alpha^2 corrections to parapositronium decay: a detailed description
We present details of our recent calculation of alpha^2 corrections to the
parapositronium decay into two photons. These corrections are rather small and
our final result for the parapositronium lifetime agrees well with the most
recent measurement. Implications for orthopositronium decays are briefly
discussed.Comment: 18 pages, late
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