425 research outputs found
Some Recent Developments in Sphalerons
We review briefly the sphaleron and list some of its properties. We summarize
some of the results in models which have an extended scalar sector. We also
present our work on models dealing with physics beyond the standard model. We
focus on the energy of the sphaleron which is important in determining the rate
of baryon number violation at the electroweak scale.Comment: Tex, 5 pages (one figure available by request), to appear in
Proceedings of Beyond the Standard Model IV, Lake Tahoe, CA, Dec. 199
Some Phenomenology of the top quark with non-standard couplings
In this talk I will use effective lagrangian and discuss possible new physics
associated with top quark.Comment: 5 pages, Latex, figures available by reques
Electroweak Sphaleron in Large Higgs Boson Mass Limit
Since the TRIVIALITY argument of the Higgs sector requires the existence of
new physics beyond the standard model, there should exist a cutoff
beyond which the standard model will breakdown. The cutoff can be determined
from the position of the Landau pole. We study the effects of this cutoff on
the energy of the electroweak sphaleron, , in the large Higgs boson
mass limit. We found that becomes arbitrarily large as the Higgs
boson mass increases. This is in contrast to the well-known result, which is
held in the standard model and a wide class of its extensions, that
is stable against the variation of the {\it bare} Higgs boson mass. The
physical meaning of this result is discussed.Comment: Iowa State University Preprint, IS-J 5268, December 1993, 10 Pages,
(TeX file
Dual solutions of Yang-Mills field theories in Minkowski space
Using spherical ansatz, we construct dual equations for non-abelian gauge
fields in Minkowski space. The analytically continued instanton is shown to
satisfy the dual equations but assumes a more ansatz. It is not the solution of
MIT second order differential equation. The symmetries of the solution function
space are examined. The relevant physics is reviewed.Comment: March/1994/IS
On the vacuum theta angle in Yang-Mills field theories
Recently, MIT group found a numerical solution to non-abelian gauge fields
which is shown to contain non-integer topological number. Using this fact,
V.V.Khoze has argued that the vacuum theta angle is zero. Here, we study this
in a complimentary way--its physical respect. The key point is MIT solution has
an infinite action. Using this, we prove the vacuum theta angle is zero at
semiclassical level.Comment: May/1994/IS
Searching for a stop-pair sample from top counting experiments at hadron colliders
The light stop pair if produced in hadron colliders and decaying through the
likely decay chain stop->chargino + b followed by chargino->neutralino + f f',
can mimic closely a top quark event when the mass of the stop is close to that
of the top quark. Because of the much lower production rate, the stop event can
be buried under the top quark event sample. In order to uncover the stop event,
specific selection cuts need to be applied. Through Monte Carlo simulation with
suitable kinematic cuts, we found that such stop event can be extracted from
the top quark sample and detected by the top quark counting experiments in the
upcoming upgraded Tevatron and LHC. However, because of the small statistics of
the Run 1 of the Tevatron, the stop signal remains hidden at Run 1.Comment: 17 pages, 4 figure
Neutrino Mixing, CP/T Violation and Textures in Four-Neutrino Models
We examine the prospects for determining the neutrino mixing matrix and for
observing CP and T violation in neutrino oscillations in four-neutrino models.
We focus on a general class of four-neutrino models with two pairs of nearly
degenerate mass eigenstates separated by approximately 1 eV, which can describe
the solar, atmospheric and LSND neutrino data. We present a general
parametrization of these models and discuss in detail the determination of the
mixing parameters and the mass matrix texture from current and future neutrino
data in the case where and each mix primarily with one other
neutrino. We find that measurable CP/T violation in long-baseline experiments,
with amplitude at the level of the LSND signal, is possible given current
experimental constraints. Also, additional oscillation effects in short- and
long-baseline experiments may be measurable in many cases. We point out that,
given separate scales for the mass-squared differences of the solar and
atmospheric oscillations, observable CP/T violation effects in neutrino
oscillations signals the existence of a sterile neutrino. We examine several
textures of the neutrino mass matrix and determine which textures can have
measurable CP/T violation in neutrino oscillations in long-baseline
experiments. We also briefly discuss some possible origins of the neutrino mass
terms in straightforward extensions of the Standard Model.Comment: 30 pages, Revtex, no figures. Reference added, ASITP preprint number
correcte
Searching for a stop-pair sample from top counting experiments at hadron colliders
The light stop pair if produced in hadron colliders and decaying through the likely decay chain stop->chargino + b followed by chargino->neutralino + f f', can mimic closely a top quark event when the mass of the stop is close to that of the top quark. Because of the much lower production rate, the stop event can be buried under the top quark event sample. In order to uncover the stop event, specific selection cuts need to be applied. Through Monte Carlo simulation with suitable kinematic cuts, we found that such stop event can be extracted from the top quark sample and detected by the top quark counting experiments in the upcoming upgraded Tevatron and LHC. However, because of the small statistics of the Run 1 of the Tevatron, the stop signal remains hidden at Run 1
On the Optimum Long Baseline for the Next Generation Neutrino Oscillation Experiments
For high energy long baseline neutrino oscillation experiments, we propose a Figure of Merit criterion to compare the statistical quality of experiments at various oscillation distances under the condition of identical detectors and a given neutrino beam. We take into account all possible experimental errors under general consideration. In this way the Figure of Merit is closely related to the usual statistical criterion of number of sigmas. We use a realistic neutrino beam for an entry level neutrino factory and a possible superbeam from a meson source and a 100 kt detector for the calculation. We considered in detail four oscillation distances, 300 km, 700 km, 2100 km and 3000 km, in the neutrino energy range of 0.5-20 GeV for a 20 GeV entry level neutrino factory and a 50 GeV superbeam. We found that the very long baselines of 2100 km and 3000 km are preferred for the neutrino factory according to the figure of merit criterion. Our results also show that, for a neutrino factory, lower primary muon energies such as 20 GeV are preferred rather than higher ones such as 30 or 50 GeV. For the superbeam, the combination of a long baseline such as 300 km and a very long baseline like 2100 km will form a complete measurement of the oscillation parameters besides the CP phase. To measure the CP phase in a superbeam, a larger detector (a factor 3 beyond what is considered in this article) and/or a higher intensity beam will be needed to put some significant constraints on the size of the CP angle
Unitarity Constraints on Anomalous Top Quark Couplings to Weak Gauge Bosons
If there is new physics associated with the top quark, it could show up as anomalous couplings of the top quark, such as Z\ttbar and W\tbbar vector and axial-vector couplings. We use the processes \ttbar\to Z^0Z^0, \ttbar\to W^+W^-, and \ttbar\to Z^0H to obtain the unitarity constraints on these anomalous couplings, and combine these constraints with those from precision electroweak data. A nonzero measurement of such an anomalous coupling will put an upper limit on the new physics scale by the unitarity condition
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