86 research outputs found
Stuckelberg Axions and the Effective Action of Anomalous Abelian Models 1. A unitarity analysis of the Higgs-axion mixing
We analyze the quantum consistency of anomalous abelian models and of their
effective field theories, rendered anomaly-free by a Wess-Zumino term, in the
case of multiple abelian symmetries. These models involve the combined
Higgs-Stuckelberg mechanism and predict a pseudoscalar axion-like field that
mixes with the goldstones of the ordinary Higgs sector. We focus our study on
the issue of unitarity of these models both before and after spontaneous
symmetry breaking and detail the set of Ward identities and the organization of
the loop expansion in the effective theory. The analysis is performed on simple
models where we show, in general, the emergence of new effective vertices
determined by certain anomalous interactions.Comment: 67 pages, 26 figures, replaced with revised final version, to appear
on JHE
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Polarized and unpolarized double prommpt photon production in next-to-leading order QCD
We calculate O({alpha}{sub s}) corrections to inclusive and isolated double prompt photon production, both for the unpolarized case, and for longitudinal polarization of the incoming hadrons. The calculation is performed using purely analytical techniques for the inclusive case, and a combination of analytical and Monte Carlo techniques to perform the phase space integration in the isolated case. A brief phenomenological study is made of the process pp {r_arrow} {gamma}{gamma}X at CMS energies appropriate for the RHIC heavy ion collider. 21 refs., 8 figs
Volcanic Stratigraphy of Hannah Point, Livingston Island, South Shetland Islands, Antarctica
The Upper Cretaceous volcanic succession of Hannah Point is the best exposure of the Antarctic Peninsula Volcanic Group on Livingston Island. The aim of the present paper is to contribute to the characterisation of the stratigraphy and petrography of this little studied succession, and briefly discuss some aspects of the eruptive style of its volcanism. The succession is about 470 m thick and is here subdivided into five lithostratigraphic units (A to E from base to top). Unit A, approximately 120 m thick, is mainly composed of polymict clast-supported volcaniclastic breccias and also includes a dacitic lava laye r. Interstratified in the breccias of this unit, there is a thin laminated devitrified layer which shows some degree of welding. Unit B, approximately 70 m thick, is almost entirely composed of volcaniclastic breccias, and includes a volcaniclastic conglomerate layer. Breccias in this unit can be subdivided into two distinct types; polymict clast-supported breccias, and monomict matrix-supported breccias rich in juvenile components and displaying incipient welding. Unit C, about 65 m thick, is mainly composed of basaltic lavas, which are interlayered with minor volcaniclastic breccias. Unit D, approximately 65 m thick, is lithologically similar to unit B, composed of an alternation of polymict clasts upported breccias and matrix-supported breccias, and includes a volcaniclastic conglomerate layer. Unit E, about 150 m thick, is mainly formed of thick andesitic lava layers. Minor basaltic dykes and a few normal faults cut the succession, and the contact between units A and B can be interpreted both as an unconformity or a fault. The matrix-supported breccias included in the succession of Hannah Point have high contents of juvenile components and incipient welding, which suggest that part of the succession is the result of pyroclastic fragmentation and emplacement from pyroclastic flows. In contrast, the polymict clast-supported breccias suggest reworking of previous deposits and deposition from cool mass flows. The lavas indicate effusive volcanic eruptions, and the absence of features indicative of subaqueous volcanism suggests that at least these portions of the succession were emplaced in a subaerial environment
Deeply Virtual Neutrino Scattering (DVNS)
We introduce the study of neutrino scattering off protons in the deeply
virtual kinematics, which describes under a unified formalism elastic and deep
inelastic neutrino scattering. A real final state photon and a recoiling
nucleon are detected in the few GeV ( GeV) region of momentum
transfer. This is performed via an extension of the notion of deeply virtual
Compton scattering, or DVCS, to the case of a neutral current exchange. The
relevance of this process and of other similar exclusive processes for the
study of neutrino interactions in neutrino factories for GeV neutrinos is
pointed out.Comment: 28 pages, 12 figures, revised final version, to appear in JHE
Particle Physics Explanations for Ultra High Energy Cosmic Ray Events
The origin of cosmic ray events with E \gsim 10^{11} GeV remains
mysterious. In this talk I briefly summarize several proposed particle physics
explanations: a breakdown of Lorentz invariance, the ``burst'' scenario,
new hadrons with masses of several GeV as primaries, and magnetic monopoles
with mass below GeV as primaries. I then describe in a little more
detail the idea that these events are due to the decays of very massive,
long--lived exotic particles.Comment: Invited plenary talk at PASCOS03, Mumbai, India, January 2003; 13
pages, 1 figur
On The Finite Temperature Chern-Simons Coefficient
We compute the exact finite temperature effective action in a 0+1-dimensional
field theory containing a topological Chern-Simons term, which has many
features in common with 2+1-dimensional Chern-Simons theories. This exact
result explains the origin and meaning of puzzling temperature dependent
coefficients found in various naive perturbative computations in the higher
dimensional models.Comment: 11 pages LaTeX; no figure
Effective Field Theory Approach to High-Temperature Thermodynamics
An effective field theory approach is developed for calculating the
thermodynamic properties of a field theory at high temperature and weak
coupling . The effective theory is the 3-dimensional field theory obtained
by dimensional reduction to the bosonic zero-frequency modes. The parameters of
the effective theory can be calculated as perturbation series in the running
coupling constant . The free energy is separated into the contributions
from the momentum scales and , respectively. The first term can be
written as a perturbation series in . If all forces are screened at the
scale , the second term can be calculated as a perturbation series in
beginning at order . The parameters of the effective theory satisfy
renormalization group equations that can be used to sum up leading logarithms
of . We apply this method to a massless scalar field with a
interaction, calculating the free energy to order and the
screening mass to order .Comment: 40 pages, LaTeX, 5 uuecoded figure
On the Convergence of Perturbative QCD at High Temperature
The free energy for QCD at high temperature is calculated to order
using effective-field-theory methods to separate the contributions from the
momentum scales and . The effects of the scale enter through the
coefficients in the effective lagrangian for the 3-dimensional effective theory
obtained by dimensional reduction. The perturbation series for these
coefficients seem to be well-behaved if the running coupling constant is
sufficiently small: . For the contribution to the free
energy from the scale , the perturbation series is well-behaved only if
is an order of magnitude smaller. The implication for
applications of perturbative QCD to the quark-gluon plasma are briefly
discussed.Comment: 12 pages, LaTe
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