6,029 research outputs found
Tau polarization effects in the CNGS tau-neutrino appearance experiments
We studied tau polarization effects on the decay distributions of tau
produced in the CNGS tau-neutrino appearance experiments. We show that energy
and angular distributions for the decay products in the laboratory frame are
significantly affected by the tau polarization. Rather strong azimuthal
asymmetry about the tau momentum axis is predicted, which may have observable
consequences in experiments even with small statistics.Comment: 5 pages, 6 eps figures, espcrc2.sty; Proceedings of the 4th
International Workshop on Neutrino-Nucleus Interactions in the Few GeV Region
(NuInt05), September 26-29, 2005, Okayama, Japa
Search for a Higgs Boson Decaying into Two Photons with the L3 Detector at LEP
A search is performed for a Higgs boson, decaying into two photons, using the
L3 data collected at centre of mass energies between = 189 and 202
GeV, corresponding to an integrated luminosity of 400 pb. The processes
, , are considered. The observed data are found to be consistent with the
expected background from standard physics processes. Limits on the branching
fraction of the Higgs boson decay into two photons as a function of the Higgs
mass are shown and a lower mass limit on a fermiophobic Higgs is derived.Comment: 3 pages, 2 postscript figures, Presented at the DPF2000 Conference,
August 9-12, 2000, The Ohio State University, Columbus, Ohi
Phase diagram of a frustrated mixed-spin ladder with diagonal exchange bonds
Using exact numerical diagonalization and the conformal field theory
approach, we study the effect of magnetic frustrations due to diagonal exchange
bonds in a system of two coupled mixed-spin Heisenberg chains. It
is established that relatively moderate frustrations are able to destroy the
ferrimagnetic state and to stabilize the critical spin-liquid phase typical for
half-integer-spin antiferromagnetic Heisenberg chains. Both phases are
separated by a narrow but finite region occupied by a critical
partially-polarized ferromagnetic phase.Comment: 5 PRB pages, 7 eps figures, to appear in Phys. Rev.
Energy Versus Magnetic-Field Diagram of the Spin-1 Haldane System with an Impurity
Energy versus magnetic-field diagram of the spin- Haldane system with an
impurity bond is studied in terms of spin-1/2 degree of freedom at the sites
neighboring the impurity bond by means of analytical method. We examine the
equivalence between the realistic Hamiltonian and the phenomenological
Hamiltonian which is composed two spin-1/2 spins representing the spin-1/2
degree of freedom. It is proved that when the strength of the impurity bond is
sufficiently weak, the two Hamiltonians are equivalent to each other, as far as
the energies of the low-lying states are concerned. We determine the
correspondence between the interaction constants in the phenomenological
Hamiltonian and those in the realistic Hamiltonian.Comment: 10 pages, plain TeX (Postscript figures are included), KU-CCS-93-00
Singe Top Production at LEP 200
We present exact tree level cross sections for the single top production
process at LEP~200. The
results reproduce roughly those obtained earlier by using the equivalent real
photon approximation and we confirm the observation that detecting a top
heavier than half the c.m.~energy is not feasible at LEP~200. The calculation
has been performed by a new automatic Feynman amplitude generator MadGraph
which produces HELAS code for the helicity amplitudes.Comment: 7 pages, 4 postscript figure
Analyticity, crossing and the absorptive parts of the one-loop contributions to the quark-quark-gluon gauge boson four-point function
Starting from the known one-loop result for the -annihilation
process with
massless quarks we employ analyticity and crossing to determine the absorptive
parts of the corresponding one-loop contributions in Deep Inelastic Scattering
(DIS) and in the Drell-Yan process (DY). Whereas the
absorptive parts generate a non-measurable phase factor in the
-annihilation channel one obtains measurable phase effects from the
one-loop contributions in the deep inelastic and in the Drell-Yan case. We
compare our results with the results of previous calculations where the
absorptive parts in DIS and in the DY process were calculated directly in the
respective channels. We also present some new results on the dispersive and
absorptive contributions of the triangle anomaly graph to the DIS process.Comment: 23 pages, 5 figures, typos corrected. Version to appear in Phys. Rev.
Thermodynamic properties of a tetramer ferro-ferro-antiferro-antiferromagnetic Ising-Heisenberg bond alternating chain as a model system for Cu(3-Clpy)(N)
Thermodynamic properties of a tetramer
ferro-ferro-antiferro-antiferromagnetic Ising-Heisenberg bond alternating chain
are investigated by the use of an exact mapping transformation technique. Exact
results for the magnetization, susceptibility and specific heat in the zero as
well as nonzero magnetic field are presented and discussed in detail. The
results obtained from the mapping are compared with the relevant experimental
data of Cu(3-Clpy)(N) (3-Clpy=3-Chloropyridine).Comment: 10 pages, 1 table, 14 figures, to be presented at CSMAG04 conferenc
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