4,361 research outputs found
Particle decay in false vacuum
We revisit the problem of decay of a metastable vacuum induced by the
presence of a particle. For the bosons of the `master field' the problem is
solved in any number of dimensions in terms of the spontaneous decay rate of
the false vacuum, while for a fermion we find a closed expression for the decay
rate in (1+1) dimensions. It is shown that in the (1+1) dimensional case an
infrared problem of one-loop correction to the decay rate of a boson is
resolved due to a cancellation between soft modes of the field. We also find
the boson decay rate in the `sine-Gordon staircase' model in the limits of
strong and weak coupling.Comment: 19 pages, 2 figure
Direct photon production from hadronic sources in high-energy heavy-ion collisions
The low direct photon production from a variety of the hadronic sources
is studied within the microscopic HSD transport approach for p+C, p+Pb and
Pb+Pb collisions at 160 A GeV. The direct photon emission from elementary
hadronic scatterings as well as meson-meson bremsstrahlung are incorporated.
The influence of in-medium effects such as a collisional broadening of the
vector-meson spectral functions on the photon emission rate is found to be
hardly observable in the final spectra which are dominated by bremsstrahlung
type processes. The uncertainties in the subtraction of the 'background' from
the photon decay of hadronic resonances inside the hot and dense fireball is
investigated, additionally. Our findings are relevant for the interpretation
and extraction of experimental data on direct photon production at low .Comment: 25 pages, 10 figures, to be published in Phys. Rev.
Physics at Hadron Colliders
In this paper we summarize the results of the theory working group dedicated
to the analysis of production at hadron colliders.Comment: 7 pages, LaTe
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