59 research outputs found
Precision Tests of Electroweak Physics
We review the current status of precision electroweak measurements and the
constraints they impose on new physics. We perform a model independent analysis
using the STU-formalism of Ref. 1, and then discuss how the Z-pole data from
LEP and SLD can be used to constrain models that are not covered within that
framework.Comment: 1 cover page + 8 pages, 8 postscript figures, LaTeX2e,
ws-p9-75x6-50.cls, Talk presented at Hadron 13, Mumbai, India, January 14-20,
199
Charge assignments in multiple-U(1) gauge theories
We discuss the choice of gauge field basis in multiple-U(1) gauge theories.
We find that there is a preferred basis, specified by the charge orthogonality
condition, in which the U(1) gauge fields do not mix under one-loop
renormalization group running.Comment: 7 pages, LaTe
Constraints on R-parity violating couplings from LEP/SLD hadronic observables
We analyze the one loop corrections to hadronic Z decays in an R-parity
violating extension to the Minimal Supersymmetric Standard Model (MSSM).
Performing a global fit to all the hadronic observables at the Z-peak, we
obtain stringent constraints on the R-violating couplings constants lambda' and
lambda''. As a result of the strong constraints from the b asymmetry parameters
A_b and A_FB(b), we find that the couplings lambda'{i31}, lambda'{i32}, and
lambda''{321} are ruled out at the 1 sigma level, and that lambda'{i33} and
lambda''{33i} are ruled out at the 2 sigma level. We also obtain Bayesian
confidence limits for the R-violating couplings.Comment: 30 pages, 19 postscript figures, REVTeX, new section 8 on Bayesian
confidence limits adde
Predictions of and in an Asymptotically Non-Free Theory
We discuss an extention of the Minimal Supersymmetric Standard Model (MSSM)
with the 4th and anti-4th generations which have
invariant masses. Due to the the extra generations, all three running gauge
couplings become asymptotically non--free while preserving gauge coupling
unification at the GUT scale. We show that due to the asymptotically non--free
character of the gauge couplings: (1) the top and bottom Yukawa couplings are
strongly focused onto infrared fixed points as they are evolved down in scale
making their values at \mu=\mz insensitive to their initial values at
\mu=\mgut; (2) the model predicts \R(\mz) \equiv Y_b/Y_\tau |_{\mu
=\mz}\approx 1.8, which is consistent with the experimental value provided we
take the ratio of Yukawa couplings at the GUT scale to be \R(\mgut) =
Y_b/Y_\tau |_{\mu = \mgut} = 1/3; (3) the mass prediction comes out to be
\mt\approx 180\,\GeV which is also consistent with experiment.Comment: 20 pgs. 7 figures. Latex2e. othersym.sty, suceqn.sty include
The NuTeV Anomaly, Neutrino Mixing, and a Heavy Higgs Boson
Recent results from the NuTeV experiment at Fermilab and the deviation of the
Z invisible width, measured at LEP/SLC, from its Standard Model (SM) prediction
suggest the suppression of neutrino-Z couplings. Such suppressions occur
naturally in models which mix the neutrinos with heavy gauge singlet states. We
postulate a universal suppression of the Z-nu-nu couplings by a factor of
(1-epsilon) and perform a fit to the Z-pole and NuTeV observables with epsilon
and the oblique correction parameters S and T. Compared to a fit with S and T
only, inclusion of epsilon leads to a dramatic improvement in the quality of
the fit. The values of S and T preferred by the fit can be obtained within the
SM by a simple increase in the Higgs boson mass. However, if the W mass is also
included in the fit, a non-zero U parameter becomes necessary which cannot be
supplied within the SM. The preferred value of epsilon suggests that the seesaw
mechanism may not be the reason why neutrinos are so light.Comment: 19 pages, REVTeX4, 8 postscript figures. Updated references. Typos
correcte
Constraints on Two-Higgs Doublet Models at Large tan{beta} from W and Z decays
We study constraints on type-II two Higgs doublet models at large tan{beta}
from LEP/SLD Z-pole data and from lepton universality violation in W decay. We
perform a global fit and find that, in the context of Z decay, the LEP/SLD
experimental values for lepton universality violation, R_b, and A_b all
somewhat disfavor the model. Contributions from the neutral Higgs sector can be
used to constrain the scalar-pseudoscalar Higgs mass splittings. Contributions
from the charged Higgs sector allow us to constrain the charged Higgs mass. For
tan{beta}=100 we obtain the 1 sigma classical (Bayesian) bounds of m_{H+} > 670
GeV (370 GeV) and 1 > m_{h0}/m_{A0} > 0.68 (0.64). The 2 sigma bounds are weak.
Currently, the Tevatron experimental limits on lepton universality violation in
W decay provide no significant constraint on the Higgs sector.Comment: 26 pages, 9 postscript figures, REVTe
Constraints on Topcolor Assisted Technicolor Models from Vertex Corrections
We use the LEP/SLD data to place constraints on Topcolor Assisted Technicolor
Models. We find that due to a large negative shift in R_b induced by charged
top-pion exchange, it is difficult to make the models compatible with
experiment.Comment: 16 pages, 2 figure
Expression of COX-2, NF-ÎșB-p65, NF-ÎșB-p50 and IKKα in malignant and adjacent normal human colorectal tissue
Peer reviewedPublisher PD
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