378 research outputs found
Physics at e-e- Colliders
An overview of the physics motivations for e-e- colliders is presented.Comment: 10 pages. Opening lecture of the 3nd International Workshop on
Electron-Electron Interactions at TeV Energies (e-e-99), University of
California, Santa Cruz, 10-12 December 199
Decay of the Z Boson into Scalar Particles
In extensions of the standard model, light scalar particles are often
possible because of symmetry considerations. We study the decay of the Z boson
into such particles. In particular, we consider for illustration the scalar
sector of a recently proposed model of the 17-keV neutrino which satisfies all
laboratory, astrophysical, and cosmological constraints.Comment: 11 pages (2 figures, not included) (Revised, Oct 1992). Some
equations have been corrected and 1 figure has been eliminate
CP Violation in the Top-Quark Pair Production at a Next Linear Collider
We provide a detailed, model-independent, study for CP violation effects due
to the T-odd top-quark electric dipole moment (EDM) and weak dipole moment
(WDM) in the top-quark pair production via and two-photon annihilation
at a next linear collider (NLC). There are two methods in detecting CP
violation effects in these processes. One method makes use of measurements of
various spin correlations in the final decay products of the produced top-quark
pair, while the other is to measure various CP-odd polarization asymmetry
effects of the initial states. In the case only the first method can
be used, and in the case both methods can be employed. We
provide a complete classification of angular correlations of the and
decay products under CP and CP\tilde{T} which greatly faciliate CP
tests in the mode. Concentrating on the second method with the Compton
back-scattered high-energetic laser light off the electron or positron beam in
the two-photon mode, we construct two CP-odd and CP\tilde{T}-even initial
polarization configurations and apply them to investigating CP-violating
effects due to the top-quark EDM. With a typical set of experimental parameters
at the NLC, we compare the 1-\sigma sensitivities to the top-quark EDM and WDM
in the mode and the two-photon mode. Some model expectation values of
the T-odd parameters are compared with the results.Comment: 45 pages(LaTeX), 10 eps figures, uses epsfig.st
Frodo Links Dishevelled to the p120-Catenin/Kaiso Pathway: Distinct Catenin Subfamilies Promote Wnt Signals
Summaryp120-catenin is an Arm repeat protein that interacts with varied components such as cadherin, small G proteins, kinases, and the Kaiso transcriptional repressor. Despite recent advances in understanding the roles that p120-catenin and Kaiso play in downstream modulation of Wnt/β-catenin signaling, the identity of the upstream regulators of the p120-catenin/Kaiso pathway have remained unclear. Here, we find that p120-catenin binds Frodo, which itself interacts with the Wnt pathway protein Dishevelled (Dsh). In Xenopus laevis, we demonstrate that Wnt signals result in Frodo-mediated stabilization of p120-catenin, which, in turn, promotes Kaiso sequestration or removal from the nucleus. Our results point to Dsh and Frodo as upstream regulators of the p120-catenin/Kaiso signaling pathway. Importantly, this suggests that Wnt signals acting through Dsh regulate the stability of p120-catenin in addition to that of β-catenin, and that each catenin promotes its respective signal in parallel to regulate distinct, as well as shared, direct downstream gene targets
Constraints on Light Top Squark from - mixing
We discuss the constraints on the mass of the lighter top squark from \bbbar\
mixing in the minimal supersymmetric standard model. A light top squark whose
mass is less than half of the -boson mass has not yet been excluded from
direct search experiments at LEP. However, the existence of the light top
squark may exceedingly enhance \bbbar\ mixing, owing to the box diagrams
exchanging the charginos and the up-type squarks. We show that for a sizable
region of parameter space the light top squark contribution to \bbbar\ mixing
becomes the same order of magnitude as the standard -boson contribution.
Taking into account the experimental results for \bbbar\ and \kkbar\ mixings,
the existence of the light top squark is excluded in an appreciable region of
the parameter space which LEP experiments have not ruled out.Comment: 8 pages latex file, 2 figure
Fermionic decays of sfermions: a complete discussion at one-loop order
We present a definition of an on-shell renormalization scheme for the
sfermion and chargino-neutralino sector of the Minimal Supersymmetric Standard
Model (MSSM). Then, apply this renormalization framework to the interaction
between charginos/neutralinos and sfermions. A kind of universal corrections is
identified, which allow to define effective chargino/neutralino coupling
matrices. In turn, these interactions generate (universal) non-decoupling terms
that grow as the logarithm of the heavy mass. Therefore the full MSSM spectrum
must be taken into account in the computation of radiative corrections to
observables involving these interactions. As an application we analyze the full
one-loop electroweak radiative corrections to the partial decay widths
\Gamma(\tilde{f} -> f\neut) and \Gamma(\tilde{f} -> f'\cplus) for all sfermion
flavours and generations. These are combined with the QCD corrections to
compute the corrected branching ratios of sfermions. It turns out that the
electroweak corrections can have an important impact on the partial decay
widths, as well as the branching ratios, in wide regions of the parameter
space. The precise value of the corrections is strongly dependent on the
correlation between the different particle masses.Comment: LaTeX 53 pages, 22 figures, 3 tables. Typos correcte
Role of Light Vector Mesons in the Heavy Particle Chiral Lagrangian
We give the general framework for adding "light" vector particles to the
heavy hadron effective chiral Lagrangian. This has strong motivations both from
the phenomenological and aesthetic standpoints. An application to the already
observed D \rightarrow \overbar{K^*} weak transition amplitude is discussed.Comment: 19 pages, LaTeX documen
Chiral Estimates of Strong CP Violation Revisited
The effects of the CP violating term in the QCD Lagrangian upon low
energy hadronic phenomenology are reconsidered. Strong CP violating
interactions among Goldstone bosons and octet baryons are incorporated into an
effective chiral Lagrangian framework. The term's impact upon the
decays and is then investigated but
found to be extremely small. A refined model independent estimate of
nonanalytic contributions to the neutron electric dipole moment is also
determined using velocity dependent Baryon Chiral Perturbation Theory. We
obtain the approximate upper bound .Comment: 11 pages with 3 figures not included but available upon request,
CALT-68-184
Effects of Possible Transitions in Neutral Meson Decays}
We explore the possibility that the existing data on like-sign dileptons at
the resonance consist of events arising from mixing and also from transitions. The
consequences of these nonstandard transitions for certain time-asymmetries
which are likely to be measured at the factories are studied.Comment: {\LARGE \bf 10 pages, no figures, process using latex, TIFR/TH/93-5
Quantum-Chromodynamic Potential Model for Light-Heavy Quarkonia and the Heavy Quark Effective Theory
We have investigated the spectra of light-heavy quarkonia with the use of a
quantum-chromodynamic potential model which is similar to that used earlier for
the heavy quarkonia. An essential feature of our treatment is the inclusion of
the one-loop radiative corrections to the quark-antiquark potential, which
contribute significantly to the spin-splittings among the quarkonium energy
levels. Unlike and , the potential for a light-heavy
system has a complicated dependence on the light and heavy quark masses and
, and it contains a spin-orbit mixing term. We have obtained excellent
results for the observed energy levels of , , , and , and
we are able to provide predicted results for many unobserved energy levels. Our
potential parameters for different quarkonia satisfy the constraints of quantum
chromodynamics.
We have also used our investigation to test the accuracy of the heavy quark
effective theory. We find that the heavy quark expansion yields generally good
results for the and energy levels provided that and
corrections are taken into account in the quark-antiquark
interactions. It does not, however, provide equally good results for the energy
levels of and , which indicates that the effective theory can be
applied more accurately to the quark than the quark.Comment: 17 pages of LaTeX. To appear in Physical Review D. Complete
PostScript file is available via WWW at
http://gluon.physics.wayne.edu/wsuhep/jim/heavy.p
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