6,351 research outputs found
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
A New Model for Fermion Masses in Supersymmetric Grand Unified Theories
We present a simple model for fermion mass matrices and quark mixing in the
context of supersymmetric grand unified theories and show its agreement with
experiment. Our model realizes the GUT mass relations , , in a new way and is easily consistent with values of
suggested by MSSM fits to LEP data.Comment: Latex, 8 p., ITP-SB-93-37 (revised version contains minor changes in
some wording and citations; no changes in analytic or numerical results.
Using to Probe Top Quark Couplings
Possible anomalous couplings of the top-quark to on-shell photons and gluons
are constrained by the recent results of the CLEO Collaboration on both
inclusive and exclusive radiative decays. We find that the process \bsg\
can lead to reasonable bounds on both the anomalous electric and magnetic
dipole moments of the top-quark, while essentially no limits are obtained on
the corresponding chromoelectric and chromomagnetic moments, which enter the
expression for the decay rate only through operator mixing.Comment: 10 pages plus 6 figures (available by request), LaTex,
ANL-HEP-PR-93-3
Gaseous Dark Matter Detectors
Dark Matter detectors with directional sensitivity have the potential of
yielding an unambiguous positive observation of WIMPs as well as discriminating
between galactic Dark Matter halo models. In this article, we introduce the
motivation for directional detectors, discuss the experimental techniques that
make directional detection possible, and review the status of the experimental
effort in this field.Comment: 19 pages, review on gaseous directional dark matter detectors
submitted to New Journal of Physic
Tracing CP violation in the production of top quark pairs by multiple TeV proton-proton collisions
We investigate the possibilities of searching for non-standard CP violation
in at multiple TeV collision energies. A general kinematic
analysis of the underlying partonic production processes and
in terms of their density matrices is given. We evaluate
the CP-violating parts of these matrices in two-Higgs doublet extensions of the
standard model (SM) and give results for CP asymmetries at the parton level. We
show that these asymmetries can be traced by measuring suitable observables
constructed from energies and momenta of the decay products of and . We find CP-violating effects to be of the order of and show that
possible contaminations induced by SM interactions are savely below the
expected signals.Comment: 24 pages, SLAC-PUB-6403, PITHA 93/43, 9 Figs. available upon request.
Written in LaTe
Study the effect of beam energy spread and detector resolution on the search for Higgs boson decays to invisible particles at a future e + e - circular collider
Search for CP Violation in the Decay Z -> b (b bar) g
About three million hadronic decays of the Z collected by ALEPH in the years
1991-1994 are used to search for anomalous CP violation beyond the Standard
Model in the decay Z -> b \bar{b} g. The study is performed by analyzing
angular correlations between the two quarks and the gluon in three-jet events
and by measuring the differential two-jet rate. No signal of CP violation is
found. For the combinations of anomalous CP violating couplings, and , limits of \hat{h}_b < 0.59h^{\ast}_{b} < 3.02$ are given at 95\% CL.Comment: 8 pages, 1 postscript figure, uses here.sty, epsfig.st
Search for the glueball candidates f0(1500) and fJ(1710) in gamma gamma collisions
Data taken with the ALEPH detector at LEP1 have been used to search for gamma
gamma production of the glueball candidates f0(1500) and fJ(1710) via their
decay to pi+pi-. No signal is observed and upper limits to the product of gamma
gamma width and pi+pi- branching ratio of the f0(1500) and the fJ(1710) have
been measured to be Gamma_(gamma gamma -> f0(1500)). BR(f0(1500)->pi+pi-) <
0.31 keV and Gamma_(gamma gamma -> fJ(1710)). BR(fJ(1710)->pi+pi-) < 0.55 keV
at 95% confidence level.Comment: 10 pages, 3 figure
Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV
A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay
channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7
TeV is presented. The data were collected at the LHC, with the CMS detector,
and correspond to an integrated luminosity of 4.6 inverse femtobarns. No
significant excess is observed above the background expectation, and upper
limits are set on the Higgs boson production cross section. The presence of the
standard model Higgs boson with a mass in the 270-440 GeV range is excluded at
95% confidence level.Comment: Submitted to JHE
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