4,282 research outputs found
Comparison of 1/mQ^2 Corrections in Mesons and Baryons
We extend our relativistic quark model to the study of the decay Lambda_b ->
Lambda_c ell nu and verify that the model satisfies the heavy-quark symmetry
constraints at order 1/mQ^2. We isolate a strong dependence on a parameter
which measures the relative distortion in the light-quark wave functions of the
Lambda_b and Lambda_c. This parameter and the 1/mQ^2 corrections turn out to be
small. The dependence on a corresponding parameter in the meson case leads to
large 1/mQ^2 corrections.Comment: 9 pages, LaTeX, 3 self-contained LaTeX figures in separate fil
Comment on "The Phenomenology of a Nonstandard Higgs Boson in W_L W_L Scattering"
We show that in Composite Higgs models, the coupling of the Higgs resonance
to a pair of bosons is weaker than the corresponding Standard Model
coupling, provided the Higgs arises from electroweak doublets only. This is
partly due to the effects of the nonlinear realization of the chiral symmetries
at the compositeness scale.Comment: 6 pages, BU-HEP 94-2
The MICZ-Kepler Problems in All Dimensions
The Kepler problem is a physical problem about two bodies which attract each
other by a force proportional to the inverse square of the distance. The
MICZ-Kepler problems are its natural cousins and have been previously
generalized from dimension three to dimension five. In this paper, we construct
and analyze the (quantum) MICZ-Kepler problems in all dimensions higher than
two.Comment: A minor technical error in section 5.2 (see footnote 6) is correcte
Rare K-Decays as Crucial Tests for Unified Models with Gauged Baryon Number:
In the grand-unified models based on SU(15) and SU(16) in which the quarks
and leptons are un-unified at the intermediate stages, we show that and despite the presence of leptoquark gauge bosons. Thus, the
observation of these processes in the ongoing or upcoming experiments will rule
out the models.Comment: (7 pages, LATEX, including figures drawn by LATEX) DOE-ER40200-304
CPP-5
Partially-supervised context-specific independence mixture modeling.
Partially supervised or semi-supervised learning refers to machine learning methods which fall between clustering and classification. In the context of clustering, labels can specify link and do-not-link constraints between data points in di erent ways and constrain the resulting clustering solutions. This is a very natural framework for many biological applications as some labels are often available and even very few label greatly improve clustering results. Context-specific independence models constitute a framework for simultaneous mixture estimation and model structure determination to obtain meaningful models for high-dimensional data with many, possibly uninformative, variables. Here we present the first approach for partial learning of CSI models and demonstrate the e ectiveness of modest amounts of labels for simulated data and for protein sub-family determination
Chiral Perturbation Theory for and Semileptonic Transition Matrix Elements at Zero Recoil
Heavy quark symmetry predicts the value of and transition matrix elements of the current , at zero recoil (where in the rest frame of the the or
is also at rest). We use chiral perturbation theory to compute the
leading corrections to these predictions which are generated at low momentum,
below the chiral symmetry breaking scale.Comment: 10 pages, 1 figure (not included), CALT-68-1844, MIT-CTP-217
More Effective Field Theory for Nonrelativistic Scattering
An effective field theory treatment of nucleon-nucleon scattering at low
energy shows much promise and could prove a useful tool in the study of nuclear
matter at both ordinary and extreme densities. The analysis is complicated by
the existence a large length scale --- the scattering length --- which arises
due to couplings in the short distance theory being near critical values. I
show how this can be dealt with by introducing an explicit s-channel state in
the effective field theory. The procedure is worked out analytically in a toy
example. I then demonstrate that a simple effective field theory excellently
reproduces the 1S_0 np phase shift up to the pion production threshold.Comment: 15 pages, TeX ; macros: harvmac, eps
Baryons Containing a Heavy Quark as Solitons
The possibility of interpreting baryons containing a single heavy quark as
bound states of solitons (that arise in the nonlinear sigma model) and heavy
mesons is explored. Particular attention is paid to the parity of the bound
states and to the role of heavy quark symmetry.Comment: 15 pages, uses phyzzx.tex and tables.tex, REVISED VERSION: Some of
the results have changed because of a crucial minus sign, CALT-68-1783 and
UCSD/PTH 92-1
A Topcolor Jungle Gym
We discuss an alternative to the topcolor seesaw mechanism. In our scheme,
all the light quarks carry topcolor, and there are many composite SU(2)
doublets. This makes it possible to get the observed top quark mass and
observed breaking in a way that is quite different from the
classic seesaw mechanism. We discuss a model of this kind that arises naturally
in the context of dynamically broken topcolor. There are many composite scalars
in a theory of this kind. This has important effects on the Pagels-Stokar
relation and the Higgs mass. We find GeV, lighter than in
typical topcolor models. We also show that the electroweak singlet quarks in
such a model can be lighter than the corresponding quarks in a seesaw model.Comment: 23 pages, LaTeX, uses epsf and psfi
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