3,085 research outputs found
The Rare Top Decays and
The large value of the top quark mass implies that the rare top decays and , and and
, are kinematically allowed decays so long as or , respectively. The partial decay widths for these decay modes
are calculated in the standard model. The partial widths depend sensitively on
the precise value of the top quark mass. The branching ratio for is as much as for , and could be
observable at LHC. The rare decay modes and are highly GIM-suppressed, and thus provide a means for testing the GIM
mechanism for three generations of quarks in the u, c, t sector.Comment: 19 pages, latex, t->bWZ corrected, previous literature on t->bWZ
cited, t->cWW unchange
Radial Velocity along the Voyager 1 Trajectory: The Effect of Solar Cycle
As Voyager 1 and Voyager 2 are approaching the heliopause (HP)—the boundary between the solar wind (SW) and the local interstellar medium (LISM)—we expect new, unknown features of the heliospheric interface to be revealed. A seeming puzzle reported recently by Krimigis et al. concerns the unusually low, even negative, radial velocity components derived from the energetic ion distribution. Steady-state plasma models of the inner heliosheath (IHS) show that the radial velocity should not be equal to zero even at the surface of the HP. Here we demonstrate that the velocity distributions observed by Voyager 1 are consistent with time-dependent simulations of the SW-LISM interaction. In this Letter, we analyze the results from a numerical model of the large-scale heliosphere that includes solar cycle effects. Our simulations show that prolonged periods of low to negative radial velocity can exist in the IHS at substantial distances from the HP. It is also shown that Voyager 1 was more likely to observe such regions than Voyager 2
Radiative Tau Decays with One Pseudoscalar Meson
We have calculated the decay . We present
the photon energy spectrum, the meson-photon invariant mass spectrum and the
integrated rate as a function of a photon energy cut or an invariant mass cut.
Both the internal bremsstrahlung and the structure dependent radiation have
been taken into account. To this aim we have parametrized the form factors
and , which determine the structure dependent radiation. Observables
especially suited for the measurement of the structure dependent form factors
are found and implications on the width of the discussed.Comment: p.20, TTP93-1, LaTe
Dominant Three-Body Decays of a Heavy Higgs and Top Quark
We calculate the dominant three body Higgs decays, and , in the Standard Model. We
find that the branching ratios of these decays are of the order of few percent
for large Higgs masses. We comment on the behaviour of the partial decay width
below the threshold.
Numerical results of the following three body top decays, and , are also given. We discuss the feasibility of
observing these Higgs and top decays at future high energy colliders.Comment: 19 pages (13 Figs can be sent by request), TeX, MZ-TH/92-2
Closed orbit correction at synchrotrons for symmetric and near-symmetric lattices
This contribution compiles the benefits of lattice symmetry in the context of
closed orbit correction. A symmetric arrangement of BPMs and correctors results
in structured orbit response matrices of Circulant or block Circulant type.
These forms of matrices provide favorable properties in terms of computational
complexity, information compression and interpretation of mathematical vector
spaces of BPMs and correctors. For broken symmetries, a nearest-Circulant
approximation is introduced and the practical advantages of symmetry
exploitation are demonstrated with the help of simulations and experiments in
the context of FAIR synchrotrons
Relativistic calculations of pionic and kaonic atoms hyperfine structure
We present the relativistic calculation of the hyperfine structure in pionic
and kaonic atoms. A perturbation method has been applied to the Klein-Gordon
equation to take into account the relativistic corrections. The perturbation
operator has been obtained \textit{via} a multipole expansion of the nuclear
electromagnetic potential. The hyperfine structure of pionic and kaonic atoms
provide an additional term in the quantum electrodynamics calculation of the
energy transition of these systems. Such a correction is required for a recent
measurement of the pion mass
Consistency tests of AMPCALCULATOR and chiral amplitudes in SU(3) Chiral Perturbation Theory: A tutorial based approach
Ampcalculator is a Mathematica based program that was made publicly available
some time ago by Unterdorfer and Ecker. It enables the user to compute several
processes at one-loop (upto ) in SU(3) chiral perturbation theory. They
include computing matrix elements and form factors for strong and non-leptonic
weak processes with at most six external states. It was used to compute some
novel processes and was tested against well-known results by the original
authors. Here we present the results of several thorough checks of the package.
Exhaustive checks performed by the original authors are not publicly available,
and hence the present effort. Some new results are obtained from the software
especially in the kaon odd-intrinsic parity non-leptonic decay sector involving
the coupling . Another illustrative set of amplitudes at tree level we
provide is in the context of -decays with several mesons including quark
mass effects, of use to the BELLE experiment. All eight meson-meson scattering
amplitudes have been checked. Kaon-Compton amplitude has been checked and a
minor error in published results has been pointed out. This exercise is a
tutorial based one, wherein several input and output notebooks are also being
made available as ancillary files on the arXiv. Some of the additional
notebooks we provide contain explicit expressions that we have used for
comparison with established results. The purpose is to encourage users to apply
the software to suit their specific needs. An automatic amplitude generator of
this type can provide error-free outputs that could be used as inputs for
further simplification, and used in varied scenarios such as applications of
chiral perturbation theory at finite temperature, density and volume. This can
also be used by students as a learning aid in low-energy hadron dynamics.Comment: 25 pages, plain latex, corresponds to version to appear in EPJA,
additional ancillary files adde
Excitation of nonlinear two-dimensional wake waves in radially-nonuniform plasma
It is shown that an undesirable curvature of the wave front of
two-dimensional nonlinear wake wave excited in uniform plasma by a relativistic
charged bunch or laser pulse may be compensated by radial change of the
equilibrium plasma density.Comment: 6 pages, 4 figure
The Kaon Parameter in the Chiral Limit
We introduce four-point functions in the hadronic ladder resummation approach
to large QCD Green functions. We determine the relevant one to calculate
the kaon parameter in the chiral limit. This four-point function contains
both the large momenta QCD OPE and the small momenta ChPT at NLO limits,
analytically. We get . We also give the ChPT
result at NLO for the relevant four-point function to calculate outside
the chiral limit, while the leading QCD OPE is the same as the chiral limit
one.Comment: 17 page
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