1,156 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.
Electroweak Measurements
The measurements of electroweak sector of the Standard Model are presented,
including most recent results from LEP, Tevatron and HERA colliders. The
robustness of the Standard Model is illustrated with the precision
measurements, the electroweak fits and the comparisons to the results obtained
from low energy experiments. The status of the measurements of the boson
properties and rare production processes involving weak bosons at colliders is
examined, together with the measurements of the electroweak parameters in
collisions.Comment: 12 pages, Proceedings of "Lepton-Photon 2005", Upsalla, Swede
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
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
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
Calculation of the One- and Two-Loop Lamb Shift for Arbitrary Excited Hydrogenic States
General expressions for quantum electrodynamic corrections to the one-loop
self-energy [of order alpha(Zalpha)^6] and for the two-loop Lamb shift [of
order alpha^2(Z\alpha)^] are derived. The latter includes all diagrams with
closed fermion loops. The general results are valid for arbitrary excited non-S
hydrogenic states and for the normalized Lamb shift difference of S states,
defined as Delta_n = n^3 DeltaE(nS) - DeltaE(1S). We present numerical results
for one-loop and two-loop corrections for excited S, P and D states. In
particular, the normalized Lamb shift difference of S states is calculated with
an uncertainty of order 0.1 kHz.Comment: 4 pages, RevTe
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
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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