2,281 research outputs found
Light quark and charm interplay in the Dalitz-plot analysis of hadronic decays in FOCUS
The potentiality of interpreting the D-meson decay-dynamics has revealed
itself to be strongly dependent on our understanding of the light-meson sector.
The statistics collected by FOCUS is already at a level that manifests
parametrization problems for scalar particles. In this paper the first
application of the K-matrix approach in the charm sector is illustrated and
preliminary results on the D+ and Ds decays to three pions are shown.Comment: 9 pages, 7 figures, Invited talk at the Scalar Meson Worksho
Collective coordinates of the Skyrme model coupled with fermions
The problem of construction of fiber bundle over the moduli space of the
Skyrme model is considered. We analyse an extension of the original Skyrme
model which includes the minimal interaction with fermions. An analogy with
modili space of the fermion-monopole system is used to construct a fiber bundle
structure over the skyrmion moduli space. The possibility of the non-trivial
holonomy appearance is considered. It is shown that the effect of the fermion
interaction turns the -skyrmion moduli space into a real vector bundle with
natural connection.Comment: 10 page
Extension of Pack Method for Compressive Tests
The pack method for determining compressive stress-strain graphs described in NACA Report No. 649 has been modified to extend it's application to thinner gages and stronger materials. The principal modifications consisted in the provision of additional support against instability cementing the specimens of the pack together with fused shellac and the provision of special clamps to hold the specimens together while the test is in progress. The shellac was found to increase the buckling load of the pack without any appreciable effect on the compressive stress-strain graph of the material. The extended pack method described in this note has made possible the application of stresses in excess of 220 kips per square inch to sheet material having a thickness of only 0.02 inch
Knot commensurability and the Berge conjecture
We investigate commensurability classes of hyperbolic knot complements in the
generic case of knots without hidden symmetries. We show that such knot
complements which are commensurable are cyclically commensurable, and that
there are at most hyperbolic knot complements in a cyclic commensurability
class. Moreover if two hyperbolic knots have cyclically commensurable
complements, then they are fibered with the same genus and are chiral. A
characterisation of cyclic commensurability classes of complements of periodic
knots is also given. In the non-periodic case, we reduce the characterisation
of cyclic commensurability classes to a generalization of the Berge conjecture.Comment: v3: This version is reorganized with minor errors fixed. Proposition
4.1, Corollary 4.2, and Proposition 5.8 were added. Question 7.2 was upgraded
to Theorem 7.2. 30 pages, 1 figur
Derivative Expansion and the Effective Action for the Abelian Chern-Simons Theory at Higher Orders
We study systematically the higher order corrections to the parity violating
part of the effective action for the Abelian Chern-Simons theory in 2+1
dimensions, using the method of derivative expansion. We explicitly calculate
the parity violating parts of the quadratic, cubic and the quartic terms (in
fields) of the effective action. We show that each of these actions can be
summed, in principle, to all orders in the derivatives. However, such a
structure is complicated and not very useful. On the other hand, at every order
in the powers of the derivatives, we show that the effective action can also be
summed to all orders in the fields. The resulting actions can be expressed in
terms of the leading order effective action in the static limit. We prove gauge
invariance, both large and small of the resulting effective actions. Various
other features of the theory are also brought out.Comment: 36 page
Non-trivial Infrared Structure in (2+1)-dimensional Quantum Electrodynamics
We show that the gauge-fermion interaction in multiflavour
-dimensional quantum electrodynamics with a finite infrared cut-off is
responsible for non-fermi liquid behaviour in the infrared, in the sense of
leading to the existence of a non-trivial fixed point at zero momentum, as well
as to a significant slowing down of the running of the coupling at intermediate
scales as compared with previous analyses on the subject. Both these features
constitute deviations from fermi-liquid theory. Our discussion is based on the
leading- resummed solution for the wave-function renormalization of the
Schwinger-Dyson equations . The present work completes and confirms the
expectations of an earlier work by two of the authors (I.J.R.A. and N.E.M.) on
the non-trivial infrared structure of the theory.Comment: 10 pages (LaTex), 5 figures (Postscript
Generation of ultrashort electrical pulses in semiconductor waveguides
We report a novel device capable of generating ultrashort electrical pulses on a coplanar waveguide (CPW) by means of optical rectification. The device consists of a completely passive GaAs-based optical waveguide, which is velocity matched to a CPW line. Optical pulses are injected into the device and electrical pulses are collected at the output. Experimental results obtained in the laboratory show the potential of this device for high speed optical-to-electrical conversion
Dynamical Symmetry Breaking With a Fourth Generation
Adding a fourth generation to the Standard Model and assuming it to be valid
up to some cutoff \Lambda, we show that electroweak symmetry is broken by
radiative corrections due to the fourth generation. The effects of the fourth
generation are isolated using a Lagrangian with a genuine scalar without
self-interactions at the classical level. For masses of the fourth generation
consistent with electroweak precision data (including the B \rightarrow K \pi\
CP asymmetries) we obtain a Higgs mass of the order of a few hundreds GeV and a
cutoff \Lambda\ around 1-2 TeV. We study the reliability of the perturbative
treatment used to obtain these results taking into account the running of the
Yukawa couplings of the fourth quark generation with the aid of the
Renormalization Group (RG) equations, finding similar allowed values for the
Higgs mass but a slightly lower cut-off due to the breaking of the perturbative
regime. Such low cut-off means that the effects of new physics needed to
describe electroweak interactions at energy above \Lambda\ should be measurable
at the LHC. We use the minimal supersymmetric extension of the standard model
with four generations as an explicit example of models realizing the dynamical
electroweak symmetry breaking by radiative corrections and containing new
physics. Here, the cutoff is replaced by the masses of the squarks and
electroweak symmetry breaking by radiative corrections requires the squark
masses to be of the order of 1 TeV.Comment: 20 pages, 7 figures. New section adde
Dynamical Mass Generation in a Finite-Temperature Abelian Gauge Theory
We write down the gap equation for the fermion self-energy in a
finite-temperature abelian gauge theory in three dimensions. The instantaneous
approximation is relaxed, momentum-dependent fermion and photon self-energies
are considered, and the corresponding Schwinger-Dyson equation is solved
numerically. The relation between the zero-momentum and zero-temperature
fermion self-energy and the critical temperature T_c, above which there is no
dynamical mass generation, is then studied. We also investigate the effect
which the number of fermion flavours N_f has on the results, and we give the
phase diagram of the theory with respect to T and N_f.Comment: 20 LaTeX pages, 4 postscript figures in a single file, version to
appear in Physical Review
Three-body dispersion-relation N/D equations for the coupled decay channels ppbar (J^{PC}=0^{-+}) --> pi^0 pi^0 pi^0, eta pi^0 pi^0, eta eta pi^0, K Kbar pi^0
During several years the data on different channels ppbar (J^{PC}=0^{-+}) -->
3 mesons presented by Crystal Barrel Collaboration were successfully analyzed
by extracting the leading amplitude singularities - pole singularities - with
the aim to obtain information about two-meson resonances. But these analyses do
not take into account three-body final state interactions (FSI) in an
explicitly correct way. This paper is devoted to the consideration of this
problem.Comment: 16 pages, no figure
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