3,012 research outputs found
How Big Can Anomalous W Couplings Be?
Conventional wisdom has it that anomalous gauge-boson self-couplings can be
at most a percent or so in size. We test this wisdom by computing these
couplings at one loop in a generic renormalizable model of new physics. (For
technical reasons we consider the CP-violating couplings here, but our results
apply more generally.) By surveying the parameter space we find that the
largest couplings (several percent) are obtained when the new particles are at
the weak scale. For heavy new physics we compare our findings with expectations
based on an effective-lagrangian analysis. We find general patterns of induced
couplings which robustly reflect the nature of the underlying physics. We build
representative models for which the new physics could be first detected in the
anomalous gauge couplings.Comment: 40 pages, 11 figures, (dvi file and figures combined into a uuencoded
compressed file), (We correct an error in eq. 39 and its associated figure
(9). No changes at all to the text.), McGill-93/40, UQAM-PHE-93/03,
NEIPH-93-00
The Standard Model in Strong Fields: Electroweak Radiative Corrections for Highly Charged Ions
Electroweak radiative corrections to the matrix elements are calculated for highly charged hydrogenlike ions. These
matrix elements constitute the basis for the description of the most parity
nonconserving (PNC) processes in atomic physics. The operator
represents the parity nonconserving relativistic effective atomic Hamiltonian
at the tree level. The deviation of these calculations from the calculations
valid for the momentum transfer demonstrates the effect of the strong
field, characterized by the momentum transfer ( is the
electron mass). This allows for a test of the Standard Model in the presence of
strong fields in experiments with highly charged ions.Comment: 27 LaTex page
R_b and New Physics: A Comprehensive Analysis
We survey the implications for new physics of the discrepancy between the LEP
measurement of and its Standard Model prediction. Two broad classes of
models are considered: () those in which new Z\bbar b couplings arise at
tree level, through or -quark mixing with new particles, and ()
those in which new scalars and fermions alter the Z \bbar b vertex at one
loop. We keep our analysis as general as possible in order to systematically
determine what kinds of features can produce corrections to of the right
sign and magnitude. We are able to identify several successful mechanisms,
which include most of those which have been recently been proposed in the
literature, as well as some earlier proposals (\eg\ supersymmetric models). By
seeing how such models appear as special cases of our general treatment we are
able to shed light on the reason for, and the robustness of, their ability to
explain .Comment: 60 pages, 8 figures, plain tex, uses epsf. Final version to appear in
Phys. Rev. D; propgating sign error corrected in eqs. 78, 87, 88, 89, 98, and
107; results unchange
Electroweak effective lagrangians
In this paper I review several aspects of the use of effective lagrangians in
(mainly) electroweak physics. The conditions under which this approach is
reliable and useful, as well as the limitations of the formalism are detailed.
Various applications are also presented.Comment: 89 page
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