95 research outputs found
Two-loop electroweak top corrections: are they under control?
The assumption that two-loop top corrections are well approximated by the
contribution is investigated. It is shown that in the case of
the ratio neutral-to-charged current amplitudes at zero momentum transfer the
terms are numerically comparable to the
contribution for realistic values of the top mass. An estimate of the
theoretical error due to unknown two-loop top effect is presented for a few
observables of LEP interest.Comment: 13 pages, LaTeX using equations, doublespace, cite macros. Hard
copies of the paper including one figure are available from
[email protected]
Analytic structure of the S-matrix for singular quantum mechanics
The analytic structure of the S-matrix of singular quantum mechanics is examined within a multichannel framework, with primary focus on its dependence with respect to a parameter (Ω) that determines the boundary conditions. Specifically, a characterization is given in terms of salient mathematical and physical properties governing its behavior. These properties involve unitarity and associated current-conserving Wronskian relations, time-reversal invariance, and Blaschke factorization. The approach leads to an interpretation of effective nonunitary solutions in singular quantum mechanics and their determination from the unitary family.Fil: Camblong, Horacio E.. University of San Francisco; Estados UnidosFil: Epele, Luis Nicolas. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto de FĂsica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de FĂsica La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de FĂsica. Laboratorio de FĂsica TeĂłrica; ArgentinaFil: Fanchiotti, Huner. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto de FĂsica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de FĂsica La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de FĂsica. Laboratorio de FĂsica TeĂłrica; ArgentinaFil: GarcĂa Canal, Carlos Alberto. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto de FĂsica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de FĂsica La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de FĂsica. Laboratorio de FĂsica TeĂłrica; Argentin
Effective Field Theory Program for Conformal Quantum Anomalies
The emergence of conformal states is established for any problem involving a
domain of scales where the long-range, SO(2,1) conformally invariant
interaction is applicable. Whenever a clear-cut separation of ultraviolet and
infrared cutoffs is in place, this renormalization mechanism produces binding
in the strong-coupling regime. A realization of this phenomenon, in the form of
dipole-bound anions, is discussed.Comment: 15 pages. Expanded, with additional calculational details. To be
published in Phys. Rev.
Thirty Years of Precision Electroweak Physics
We discuss the development of the theory of electroweak radiative corrections
and its role in testing the Standard Model, predicting the top quark mass,
constraining the Higgs boson mass, and searching for deviations that may signal
the presence of new physics.Comment: 19 pages, acknowledgments added, J.J.Sakurai Prize Talk, APS Meeting,
Albuquerque, N.M., April 2002. To appear in a future issue of Journal of
Physics
Next to Leading Order Semi-inclusive Spin Asymmetries
We have computed semi-inclusive spin asymmetries for proton and deuteron
targets including next to leading order (NLO) QCD corrections and contributions
coming from the target fragmentation region. These corrections have been
estimated using NLO fragmentation functions, parton distributions and also a
model for spin dependent fracture functions which is proposed here. We have
found that NLO corrections are small but non-negligible in a scheme where
gluons are polarised and that our estimate for target fragmentation effects
does not modify significantly charged asymmetries but affects the so called
difference asymmetries.Comment: Latex, 14 pages, 6 figures in 4 Postcript file
Evidence for Bosonic Electroweak Corrections in the Standard Model
We present strong indirect evidence for the contribution of bosonic
electroweak corrections in the Standard Model. Although important conceptually,
these corrections give subleading contributions in current high energy
experiments, and it was previously thought that they are difficult to detect.
We also discuss the separate contribution of the Higgs boson.Comment: 9 pages (LaTeX + 3 PS figures, needs psfig
Incorporation of QCD Effects in Basic Corrections of the Electroweak Theory
We study the incorporation of QCD effects in the basic electroweak
corrections \drcar, \drcarw, and \dr. They include perturbative
\Ord{\alpha\alpha_s} contributions and threshold effects. The latter
are studied in the resonance and Green-function approaches, in the framework of
dispersion relations that automatically satisfy relevant Ward identities.
Refinements in the treatment of the electroweak corrections, in both the \ms\
and the on-shell schemes of renormalization, are introduced, including the
decoupling of the top quark in certain amplitudes, its effect on
\hat{e}^2(\mz) and \sincarmz, the incorporation of recent results on the
leading irreducible \Ord{\alpha^2} corrections, and simple expressions for the
residual, i.e.\ ``non-electromagnetic'', parts of \drcar, \drcarw, and \dr. The
results are used to obtain accurate values for \mw\ and \sincarmz, as functions
of \mt\ and \mh. The higher-order effects induce shifts in these parameters
comparable to the expected experimental accuracy, and they increase the
prediction for \mt\ derived from current measurements. The \ms\ and the
on-shell calculations of \dr, in a recently proposed formulation, are compared
and found to be in excellent agreement over the wide ranges 60\GeV \leq \mh
\leq 1 \TeV, \mz \leq \mt \leq 250 \GeV.Comment: 51 pages (needs doublespace, equations, and cite styles
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