17,926 research outputs found
Z -> b\bar{b} Versus Dynamical Electroweak Symmetry Breaking involving the Top Quark
In models of dynamical electroweak symmetry breaking which sensitively
involve the third generation, such as top quark condensation, the effects of
the new dynamics can show up experimentally in Z->b\bar{b}. We compare the
sensitivity of Z->b\bar{b} and top quark production at the Tevatron to models
of the new physics. Z->b\bar{b} is a relatively more sensitive probe to new
strongly coupled U(1) gauge bosons, while it is generally less sensitive a
probe to new physics involving color octet gauge bosons as is top quark
production itself. Nonetheless, to accomodate a significant excess in
Z->b\bar{b} requires choosing model parameters that may be ruled out within run
I(b) at the Tevatron.Comment: LaTex file, 19 pages + 2 Figs., Fermilab-Pub-94/231-
Chiral Hierarchies, Compositeness and the Renormalization Group
A wide class of models involve the fine--tuning of significant hierarchies
between a strong--coupling ``compositeness'' scale, and a low energy dynamical
symmetry breaking scale. We examine the issue of whether such hierarchies are
generally endangered by Coleman--Weinberg instabilities. A careful study using
perturbative two--loop renormalization group methods finds that consistent
large hierarchies are not generally disallowed.Comment: 22 pp + 5 figs (uuencoded and submitted separately),
SSCL-Preprint-490; FERMI-PUB-93/035-
Topcolor Assisted Technicolor
A condensate, , arising from scale ``topcolor,'' in
addition to technicolor (and ETC) may naturally explain the gauge hierarchy,
the large top quark mass, and contains a rich system of testable consequences.
A triplet of strongly coupled pseudo--Nambu--Goldstone bosons, ``top-pions,''
near the top mass scale is a generic prediction of the models. A new class of
technicolor schemes and associated phenomenology is suggested in this approach.Comment: 15 Page
High Energy Particles from Monopoles Connected by Strings
Monopole-antimonopole pairs connected by strings and monopole-string networks
with strings attached to each monopole can be formed at phase transitions
in the early universe. In such hybrid defects, monopoles accelerate under the
string tension and can reach ultrarelativistic Lorentz factors, .
We study the radiation of gauge quanta by accelerating monopoles. For monopoles
with a chromomagnetic charge, we also discuss the high-energy hadron production
through emission of virtual gluons and their subsequent fragmentation into
hadrons. The relevant parameter for gauge boson radiation is , where
is the boson mass and is the proper acceleration of the monopole. For , the gauge bosons can be considered as massless and the typical energy of
the emitted quanta is . In the opposite limit, , the
radiation power is exponentially suppressed and gauge quanta are emitted with a
typical energy in a narrow range .
Cosmological monopole-string networks can produce photons and hadrons of
extremely high energies. For a wide range of parameters these energies can be
much greater than the Planck scale.Comment: 28 pages, ReVTex, 5 postscript figures. Minor changes, some
references added. Submitted to Phys. Rev.
Critical Constraints on Chiral Hierarchies
We consider the constraints that critical dynamics places on models with a
top quark condensate or strong extended technicolor (ETC). These models require
that chiral-symmetry-breaking dynamics at a high energy scale plays a
significant role in electroweak symmetry breaking. In order for there to be a
large hierarchy between the scale of the high energy dynamics and the weak
scale, the high energy theory must have a second order chiral phase transition.
If the transition is second order, then close to the transition the theory may
be described in terms of a low-energy effective Lagrangian with composite
``Higgs'' scalars. However, scalar theories in which there are more than one
coupling can have a {\it first order} phase transition instead, due to
the Coleman-Weinberg instability. Therefore, top-condensate or strong ETC
theories in which the composite scalars have more than one coupling
cannot always support a large hierarchy. In particular, if the
Nambu--Jona-Lasinio model solved in the large- limit is a good
approximation to the high-energy dynamics, then these models will not produce
acceptable electroweak symmetry breaking.Comment: 10 pages, 1 postscript figure (appended), BUHEP-92-35, HUTP-92/A05
New Strong Interactons at the Tevatron ?
Recent results from CDF indicate that the inclusive cross section for jets
with GeV is significantly higher than that predicted by QCD. We
describe here a simple flavor-universal variant of the ``coloron" model of Hill
and Parke that can accommodate such a jet excess, and which is not in
contradiction with other experimental data. As such, the model serves as a
useful baseline with which to compare both the data and other models proposed
to describe the jet excess. An interesting theoretical feature of the model is
that if the global chiral symmetries of the quarks remain unbroken in the
confining phase of the coloron interaction, it realizes the possibility that
the ordinary quarks are composite particles.Comment: added contributions to scattering cross-sections; 10
pages, LaTeX, includes 1 figure. Full postscript version at
http://smyrd.bu.edu/htfigs/htfigs.htm
Decay times in turnover statistics of single enzymes
The first passage times for enzymatic turnovers in non-equilibrium steady
state display a statistical symmetry property related to non-equilibrium
fluctuation theorems, that makes it possible to extract the chemical driving
force from single molecule trajectories in non-equilibrium steady state. Below,
we show that this system violates the general expectation that the number of
decay constants needed to fit a first passage time distribution reflects the
number of states in the escape problem. In fact, the structure of the kinetic
mechanism makes half of the decay times vanish identically from the turnover
time distribution. The terms that cancel out correspond to the eigenvalues of a
certain sub-matrix of the master equation matrix for the first exit time
problem. We discuss how these results make modeling and data analysis easier
for such systems, and how the turnovers can be measured.Comment: 4 pages, 1 figure v2: Published version, minor corrections in
response to referee comment
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