4,251 research outputs found
tau Decays to Five Mesons in TAUOLA
The tau-decay library TAUOLA has gained popularity over the last decade.
However, with the continuously increasing precision of the data, some of its
functionality has become insufficient. One of the requirements is the
implementation of decays into five mesons plus a neutrino with a realistic
decay amplitude. This note describes a step into this direction. For the 2pi-
pi+ 2pi0 mode the three decay chains tau- --> a_1- nu --> rho- (--> pi- pi0)
omega (--> pi- pi+ pi0) nu, tau- --> a_1- nu --> a_1- (--> 2pi- pi+) f_0 (-->
2pi0) nu, and tau- --> a_1- nu --> a_1- (--> pi- 2pi0) f_0 (--> pi + pi-) nu
are introduced with simple assumptions about the couplings and propagators of
the various resonances. Similar amplitudes (without the rho omega
contributions) are adopted for the pi- 4pi0 and 3pi- 2pi+ modes.
The five-pion amplitude is thus based on a simple model, which, however, can
be considered as a first realistic example. Phase-space generation includes the
possibility of presampling the omega and a_1 resonances, in one channel only,
however. This is probably sufficient for the time being, both for physics
applications and for tests.
The technical test of the new part of the generator is performed by comparing
Monte Carlo and analytical results. To this end a non-realistic, but easy to
calculate, purely scalar amplitude for the decay into five massless pions was
used.Comment: 10 page
The radiative return at small angles: virtual corrections
Virtual corrections for electron--positron annihilation into one real and one
off-shell photon of invariant mass Q^2 are evaluated. Special attention is paid
to those configurations where the real photon is collinear with the beam
direction. This calculation is an important ingredient of a Monte Carlo
program, which simulates events with tagged photons from initial-state
radiation, including NLO corrections.Comment: 8 pages, 2 figure
Spin-Lattice Relaxation in Metal-Organic Platinum(II) Complexes
The dynamics of spin-lattice relaxation (slr) of metal-organic Pt(II)
compounds is studied. Often, such systems are characterized by pronounced
zero-field splittings (zfs) of the lowest-lying triplets. Previous expressions
for the Orbach slr process do not allow to treat such splitting patterns
properly. We discuss the behavior of a modified Orbach expression for a model
system and present results of a fit of the temperature dependence of the
spin-lattice relaxation rate of Pt(2-thpy) based on the modified
expression.Comment: 9 pages, 3 figures (made from 4 .eps files), elsart.cls. Using dvips
(dvipsk 5.58f), it may be necessary to manually edit the generated file
letter.ps to change in the first line from PS-Adobe-2.0 to PS-Adobe-3.0.
Chemical Physics Letters, in pres
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