524 research outputs found
Numerical Investigations of Oscillons in 2 Dimensions
Oscillons, extremely long-living localized oscillations of a scalar field,
are studied in theories with quartic and sine-Gordon potentials in two spatial
dimensions. We present qualitative results concentrating largely on a study in
frequency space via Fourier analysis of oscillations. Oscillations take place
at a fundamental frequency just below the threshold for the production of
radiation, with exponentially suppressed harmonics. The time evolution of the
oscillation frequency points indirectly to a life time of at least 10 million
oscillations. We study also elliptical perturbations of the oscillon, which are
shown to decay. We finish by presenting results for boosted and collided
oscillons, which point to a surprising persistence and soliton-like behaviour.Comment: Matches the published version (12 pages, 34 figures
Direct Photon Identification with Artificial Neural Network in the Photon Spectrometer PHOS
A neural network method is developed to discriminate direct photons from the
neutral pion background in the PHOS spectrometer of the ALICE experiment at the
LHC collider. The neural net has been trained to distinguish different classes
of events by analyzing the energy-profile tensor of a cluster in its eigen
vector coordinate system. Monte-Carlo simulations show that this method
diminishes by an order of magnitude the probability of -meson
misidentification as a photon with respect to the direct photon identification
efficiency in the energy range up to 120 GeV.Comment: 12 pages, TeX (or Latex, etc), https://edms.cern.ch/document/406291/
Numerical Simulation of an Electroweak Oscillon
Numerical simulations of the bosonic sector of the
electroweak Standard Model in 3+1 dimensions have demonstrated the existence of
an oscillon -- an extremely long-lived, localized, oscillatory solution to the
equations of motion -- when the Higgs mass is equal to twice the boson
mass. It contains total energy roughly 30 TeV localized in a region of radius
0.05 fm. A detailed description of these numerical results is presented.Comment: 12 pages, 8 figures, uses RevTeX4; v2: expanded results section,
fixed typo
A Class of Nonperturbative Configurations in Abelian-Higgs Models: Complexity from Dynamical Symmetry Breaking
We present a numerical investigation of the dynamics of symmetry breaking in
both Abelian and non-Abelian Higgs models in three spatial
dimensions. We find a class of time-dependent, long-lived nonperturbative field
configurations within the range of parameters corresponding to type-1
superconductors, that is, with vector masses () larger than scalar masses
(). We argue that these emergent nontopological configurations are related
to oscillons found previously in other contexts. For the Abelian-Higgs model,
our lattice implementation allows us to map the range of parameter space -- the
values of -- where such configurations exist and to
follow them for times t \sim \O(10^5) m^{-1}. An investigation of their
properties for -symmetric models reveals an enormously rich structure
of resonances and mode-mode oscillations reminiscent of excited atomic states.
For the SU(2) case, we present preliminary results indicating the presence of
similar oscillonic configurations.Comment: 21 pages, 19 figures, prd, revte
Elastic and scattering in the models of unitarized pomeron
Elastic scattering amplitudes dominated by the Pomeron singularity which obey
the principal unitarity bounds at high energies are constructed and analyzed.
Confronting the models of double and triple (at ) Pomeron pole
(supplemented by some terms responsible for the low energy behaviour) with
existing experimental data on and total and differential cross
sections at GeV and GeV we are able to tune
the form of the Pomeron singularity. Actually the good agreement with those
data is received for both models though the behaviour given by the dipole model
is more preferable in some aspects. The predictions made for the LHC energy
values display, however, the quite noticeable difference between the
predictions of models at GeV. Apparently the future
results of TOTEM will be more conclusive to make a true choice.Comment: Revtex4, 8 pages, 5 figures. Text is improved, no changes in figures
and conclusions. Version to be published in Phys. Rev.
Information Content of Spontaneous Symmetry Breaking
We propose a measure of order in the context of nonequilibrium field theory
and argue that this measure, which we call relative configurational entropy
(RCE), may be used to quantify the emergence of coherent low-entropy
configurations, such as time-dependent or time-independent topological and
nontopological spatially-extended structures. As an illustration, we
investigate the nonequilibrium dynamics of spontaneous symmetry-breaking in
three spatial dimensions. In particular, we focus on a model where a real
scalar field, prepared initially in a symmetric thermal state, is quenched to a
broken-symmetric state. For a certain range of initial temperatures,
spatially-localized, long-lived structures known as oscillons emerge in
synchrony and remain until the field reaches equilibrium again. We show that
the RCE correlates with the number-density of oscillons, thus offering a
quantitative measure of the emergence of nonperturbative spatiotemporal
patterns that can be generalized to a variety of physical systems.Comment: LaTeX, 9 pages, 5 figures, 1 tabl
Emergence of Oscillons in an Expanding Background
We consider a (1+1) dimensional scalar field theory that supports oscillons,
which are localized, oscillatory, stable solutions to nonlinear equations of
motion. We study this theory in an expanding background and show that oscillons
now lose energy, but at a rate that is exponentially small when the expansion
rate is slow. We also show numerically that a universe that starts with
(almost) thermal initial conditions will cool to a final state where a
significant fraction of the energy of the universe -- on the order of 50% -- is
stored in oscillons. If this phenomenon persists in realistic models, oscillons
may have cosmological consequences.Comment: 13 pages, 4 .eps figures, uses RevTeX4; v2: clarified details of
expansion, added reference
The soft and the hard pomerons in hadron elastic scattering at small t
We consider simple-pole descriptions of soft elastic scattering for pp, pbar
p, pi+ p, pi- p, K+ p and K- p. We work at t and s small enough for
rescatterings to be neglected, and allow for the presence of a hard pomeron.
After building and discussing an exhaustive dataset, we show that simple poles
provide an excellent description of the data in the region - 0.5 GeV^2 < t <
-0.1 GeV^2, 6 GeV<sqrt(s)< 63 GeV. We show that new form factors have to be
used, and get information on the trajectories of the soft and hard pomerons.Comment: 27 pages, 9 figures, LaTeX. A few typos fixed, and references
correcte
Formation of Centauro and Strangelets in Nucleus-Nucleus Collisions at the LHC and their Identification by the ALICE Experiment
We present a phenomenological model which describes the formation of a
Centauro fireball in nucleus-nucleus interactions in the upper atmosphere and
at the LHC, and its decay to non-strange baryons and Strangelets. We describe
the CASTOR detector for the ALICE experiment at the LHC. CASTOR will probe, in
an event-by-event mode, the very forward, baryon-rich phase space 5.6 < \eta <
7.2 in 5.5 A TeV central Pb + Pb collisions. We present results of simulations
for the response of the CASTOR calorimeter, and in particular to the traversal
of Strangelets.Comment: 4 pages, 4 figures, to appear in the proceedings of the 26th ICR
Reeconstructing Sigma0 decays in STAR
Typical comparisons of data from nuclear collisions to particle production
models require a caveat for (anti)Lambda yields from experimental inability to
separate the contributions of those yields from Sigma state decays. Recent
analysis in STAR is leading toward resolving the contribution from excited
Sigma states, but the bulk contribution comes from electromagnetic decays of
the (anti)Sigma0.
In the STAR detector, photon conversions into e+e- pairs in the detector
material have been used to identify photons from pi0 decays. A similar
technique has been used here to identify photons from (anti)Sigma0 decays in
conjunction with STAR's excellent PID capabilities for finding the associated
(anti)Lambda daughters. We report here on progress toward measuring the
(anti)Sigma0 yields in various nuclear collisions at RHIC.Comment: 8 pages, 5 figures, proceedings of Hot Quarks 2004 workshop,
submitted to J. Phys.
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