2,633 research outputs found
D-Meson Mixing in Broken SU(3)
A fit of amplitudes to the experimental branching ratios to two mesons is
used to construct a new estimate of neutral mixing which includes
breaking. The result is dominated by the experimental uncertainties. This
suggests that the charm sector may not be as sensitive to new physics as
previously thought and that long-distance calculations may not be useful.Comment: 12 pages, LaTeX, no figure
Massless versus Kaluza-Klein Gravitons at the LHC
We show that the LHC will be able to differentiate between a four-dimensional
model with quantum gravity at ~1 TeV where the (massless) graviton becomes
strongly coupled to standard model particles at 1 TeV and brane world type
models with a large extra-dimensional volume and massive Kaluza-Klein
gravitons. We estimate that the 14 TeV LHC could put a limit of the order of ~5
TeV on the four dimensional Planck mass in a model independent way.Comment: 9 page
New Constraints on Chiral Gauge Theories
Recently, a new constraint on the structure of a wide class of strongly
coupled field theories has been proposed. It takes the form of an inequality
limiting the number of degrees of freedom in the infrared description of a
theory to be no larger than the number of underlying, ultraviolet degrees of
freedom. Here we apply this inequality to chiral gauge theories. For some
models we find that it is always satisfied, while for others we find that the
assumption of the validity of the inequality implies a strong additional
restriction on the spectrum of massless composite particles.Comment: 11 pages, Revte
Constraining the Littlest Higgs
Little Higgs models offer a new way to address the hierarchy problem, and
give rise to a weakly-coupled Higgs sector. These theories predict the
existence of new states which are necessary to cancel the quadratic divergences
of the Standard Model. The simplest version of these models, the Littlest
Higgs, is based on an non-linear sigma model and predicts that
four new gauge bosons, a weak isosinglet quark, , with , as well as
an isotriplet scalar field exist at the TeV scale. We consider the
contributions of these new states to precision electroweak observables, and
examine their production at the Tevatron. We thoroughly explore the parameter
space of this model and find that small regions are allowed by the precision
data where the model parameters take on their natural values. These regions
are, however, excluded by the Tevatron data. Combined, the direct and indirect
effects of these new states constrain the `decay constant' f\gsim 3.5 TeV and
m_{t'}\gsim 7 TeV. These bounds imply that significant fine-tuning be
present in order for this model to resolve the hierarchy problem.Comment: 31 pgs, 26 figures; bound on t' mass fixed to mt'>2f, conclusions
unchange
Naturalness in the quark-meson coupling model
The quark-meson coupling (QMC) model is examined using Georgi's ``naive
dimensional analysis''. We argue that the QMC model is quite natural as an
effective field theory for nuclei.Comment: 11pages, no fig., submitted to Phys. Lett.
Unimagined Imaginary Parts in Heavy Quark Effective Field Theory
We argue that the imaginary parts of the anomalous dimensions in the
multiparticle sectors of heavy quark effective field theory may be removed by a
suitable redefinition of the multiparticle states. The connection between the
imaginary parts of the anomalous dimensions and the interquark potential is
pointed outComment: 14 Pages, LaTeX, HUTP-93/A009, IKDA 93/
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