2,198 research outputs found
Development of a systematic approach to conversion of the ileoanal pouch into continent ileostomy
Based on practical experience, a systematic approach to conversion of ileal J-pouches into continent ileostomies is developed by defining three types of conversion surgery, each with two subtypes. Type 1 refers to conversion without pouch reconstruction, type 2 to partial pouch reconstruction, and type 3 to complete pouch reconstruction. The subdivisions (a and b) take into account whether the afferent loop of the former pelvic pouch (a) or a higher ileal/jejunal segment of the small intestine (b) is used in conversion and/or reconstruction. The six resulting surgical variants are shown in schematic illustrations with accompanying descriptions of technical details to provide the specialized surgeon with comprehensive technical guidance
FCNC in left-right symmetric theories and constraints on the right-handed scale
We revise the limits on the FCNC higgses in manifestly left-right symmetric
theories. It is shown that the combination of the Kobayashi-Maskawa
CP-violation with the tree level higgs exchange gives very large
contribution to the CP-violating parameter. It leads to the new
strong constraint on the FCNC higgs mass, M>50- 100 TeV, enhanced by factor of
the order . Being addressed to the supersymmetric left-right
models, FCNC problem requires both right-handed scale and supersymmetric mass
parameters be heavier than 50 TeV for . The most relaxed case
corresponds to where right-handed scale can be of the
order of few TeV.Comment: 11 pages, latex, 3 figure
Radiative Kaon Decays and Direct CP Violation
It is stressed that a measurement of the electric dipole amplitude for direct
photon emission in \kpm decays through its interference with inner
bremsstrahlung is important for differentiating among various models. Effects
of amplitude CP violation in the radiative decays of the charged kaon are
analyzed in the Standard Model in conjunction with the large approach. We
point out that gluon and electromagnetic penguin contributions to the
CP-violating asymmetry between the Dalitz plots of \kpm are of equal weight.
The magnitude of CP asymmetry ranges from to when the photon energy in the kaon rest frame varies from 50 MeV to
170 MeV.Comment: Latex, 11 pages, ITP-SB-93-36, IP-ASTP-22-9
The vector form factor of the pion from unitarity and analyticity: a model-independent approach
We study a model-independent parameterization of the vector pion form factor
that arises from the constraints of analyticity and unitarity. Our description
should be suitable up to sqrt(s) ~ 1.2 GeV and allows a model-independent
determination of the mass of the rho(770) resonance, M(rho) = (775.1 +- 0.5)
MeV. We analyse the experimental data on tau(-) -> pion(-) pion(0)
neutrino(tau), in this framework, and its consequences on the low-energy
observables worked out by chiral perturbation theory. An evaluation of the
two-pion contribution to the anomalous magnetic moment of the muon, a_muon, and
to the fine structure constant, alpha(M(Z)^2), is also performed.Comment: 1+15 pages, 2 figure
Ubiquitous CP violation in a top-inspired left-right model
We explore CP violation in a Left-Right Model that reproduces the quark mass
and CKM rotation angle hierarchies in a relatively natural way by fixing the
bidoublet Higgs VEVs to be in the ratio m_b:m_t. Our model is quite general and
allows for CP to be broken by both the Higgs VEVs and the Yukawa couplings.
Despite this generality, CP violation may be parameterized in terms of two
basic phases. A very interesting feature of the model is that the mixing angles
in the right-handed sector are found to be equal to their left-handed
counterparts to a very good approximation. Furthermore, the right-handed
analogue of the usual CKM phase delta_L is found to satisfy the relation
delta_R \approx delta_L. The parameter space of the model is explored by using
an adaptive Monte Carlo algorithm and the allowed regions in parameter space
are determined by enforcing experimental constraints from the K and B systems.
This method of solution allows us to evaluate the left- and right-handed CKM
matrices numerically for various combinations of the two fundamental CP-odd
phases in the model. We find that all experimental constraints may be satisfied
with right-handed W and Flavour Changing Neutral Higgs masses as low as about 2
TeV and 7 TeV, respectively.Comment: 37 pages, 13 figure
Isospin violation and the proton's neutral weak magnetic form factor
The effects of isospin violation on the neutral weak magnetic form factor of
the proton are studied using two-flavour chiral perturbation theory. The first
nonzero contributions appear at O(p^4) in the small-momentum expansion, and the
O(p^5) corrections are also calculated. The leading contributions from an
explicit Delta(1232) isomultiplet are included as well. At such a high order in
the chiral expansion, one might have expected a large number of unknown
parameters to contribute. However, it is found that no unknown parameters can
appear within loop diagrams, and a single tree-level counterterm at O(p^4) is
sufficient to absorb all divergences. The momentum dependence of the neutral
weak magnetic form factor is not affected by this counterterm.Comment: 26 pages including 9 figure
QCD chiral Lagrangian on the lattice, strong coupling expansion and Ward identities with Wilson fermions
We discuss a general strategy to compute the coefficients of the QCD chiral
Lagrangian using lattice QCD with Wilson fermions. This procedure requires the
introduction of a lattice chiral Lagrangian as an intermediate step in the
calculation. The QCD chiral Lagrangian is then obtained by expanding the
lattice effective theory in increasing powers of the lattice spacing and the
external momenta. In order to investigate the consequences of the chiral
symmetry breaking induced by the Wilson term, we study the lattice chiral
Lagrangian at the leading order of the strong coupling and large expansion.
We show that the effects of the Wilson term can be conveniently taken into
account, in the lattice effective theory, by a suitable renormalization
procedure. In particular, we show that, at the leading order of the strong
coupling and large N expansion, the chiral symmetry is exactly recovered on the
lattice provided that the bare quark mass and the lattice operators are
properly renormalized.Comment: 45 pages, no figures. Latex fil
Kaon decay interferometry as meson dynamics probes
We discuss the time dependent interferences between and in the
decays in and , to be studied at interferometry machines
such as the -factory and LEAR. We emphasize the possibilities and the
advantages of using interferences, in comparison with width measurements, to
obtain information both on conserving and violating amplitudes.
Comparison with present data and suggestions for future experiments are made.Comment: 15 pages, in RevTex, Report INFNNA-IV-93-31, UTS-DFT-93-2
On different lagrangian formalisms for vector resonances within chiral perturbation theory
We study the relation of vector Proca field formalism and antisymmetric
tensor field formalism for spin-one resonances in the context of the large N_C
inspired chiral resonance Lagrangian systematically up to the order O(p6) and
give a transparent prescription for the transition from vector to antisymmetric
tensor Lagrangian and vice versa. We also discuss the possibility to describe
the spin-one resonances using an alternative "mixed" first order formalism,
which includes both types of fields simultaneously, and compare this one with
the former two. We also briefly comment on the compatibility of the above
lagrangian formalisms with the high-energy constraints for concrete VVP
correlator.Comment: 34 pages, 3 figure
Rare Kaon Decays
The current status of rare kaon decay experiments is reviewed. New limits in
the search for Lepton Flavor Violation are discussed, as are new measurements
of the CKM matrix.Comment: 8 pages, 3 figures, LaTeX, presented at the 3rd International
Conference on B Phyiscs and CP Violation, Taipei December 3-7, 199
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