5,571 research outputs found
Incorporating Memory Effects in Phase Separation Processes
We consider the modification of the Cahn-Hilliard equation when a time delay
process through a memory function is taken into account. We then study the
process of spinodal decomposition in fast phase transitions associated with a
conserved order parameter. Finite-time memory effects are seen to affect the
dynamics of phase transition at short times and have the effect of delaying, in
a significant way, the process of rapid growth of the order parameter that
follows a quench into the spinodal region. These effects are important in
several systems characterized by fast processes, like nonequilibrium dynamics
in the early universe and in relativistic heavy-ion collisions.Comment: 5 pages, 2 eps figures. Version in press Phys. Lett.
A Scalar Boson as a Messenger of New Physics
Quantum corrections generate a quadratically divergent mass term for the
Higgs boson in the Standard Model. Thus, if the Higgs boson has a mass of order
100 GeV, it implies the presence of a cut-off of the theory around TeV scale,
and some particles associated with the new physics may appear around the
cut-off scale . However, if is several TeV, it may be
difficult to find such particles at the LHC. In this paper, we consider a
situation in which the new physics provides relatively light particles compared
with the scale . In such a situation, we show that diphoton event and
four lepton event by the decay of the Higgs and/or a new particle have
naturally large cross section, and LHC may test the new physics in a
considerably broad parameter region even if is several TeV.Comment: 13 pages, 6 figures; v2 minor correction
Full one-loop electroweak radiative corrections to single Higgs production in e+ e-
We present the full electroweak radiative corrections to
single Higgs production in \epemt. This takes into account the full one-loop
corrections as well as the effects of hard photon radiation. We include both
the fusion and Higgs-strahlung processes. The computation is performed with the
help of {\tt GRACE-loop} where we have implemented a generalised non-linear
gauge fixing condition. The latter includes 5 gauge parameters that can be used
for checks on our results. Besides the UV, IR finiteness and gauge parameter
independence checks it proves also powerful to test our implementation of the
5-point function. We find that for a 500GeV machine and a light Higgs of mass
150GeV, the total correction is small when the results are
expressed in terms of . The total correction decreases
slightly for higher energies. For moderate centre of mass energies the total
decreases as the Higgs mass increases, reaching -10% for
GeV and GeV. In order to quantify the genuine weak
corrections we have subtracted the universal virtual and bremsstrahlung
correction from the full . We find, for GeV, a
weak correction slowly decreasing from -2% to -4% as the energy increases from
GeV to TeV after expressing the tree-level results in
terms of Comment: 16 pages, 3 figures. Only correction is a reference to a web-pag
Neutral atomic carbon in the globules of the Helix
We report detection of the 609u line of neutral atomic carbon in globules of
the Helix nebula. The measurements were made towards the position of peak CO
emission. At the same position, we obtained high-quality CO(2-1) and 13CO(2-1)
spectra and a 135" x 135" map in CO(2-1). The velocity distribution of CI shows
six narrow (1 -> 2 km/sec) components which are associated with individual
globules traced in CO. The CI column densities are 0.5 -> 1.2 x 10^16/cm^2. CI
is found to be a factor of ~6 more abundant than CO. Our estimate for the mass
of the neutral envelope is an order of magnitude larger than previous
estimates. The large abundance of CI in the Helix can be understood as a result
of the gradual photoionisation of the molecular envelope by the central star's
radiation field.Comment: 5 pages, Latex, AAS macros, 3 EPS figures, to appear in Astrophysical
Journal Letter
Energy minimization using Sobolev gradients: application to phase separation and ordering
A common problem in physics and engineering is the calculation of the minima
of energy functionals. The theory of Sobolev gradients provides an efficient
method for seeking the critical points of such a functional. We apply the
method to functionals describing coarse-grained Ginzburg-Landau models commonly
used in pattern formation and ordering processes.Comment: To appear J. Computational Physic
Prospects for detecting an in two photon processes
We argue that an experimental search for an , the first radial
excitation of the , may be carried out using the two photon
process e^+e^- \to e^+e^- \gamma \gamma \ra e^+e^-\eta_c'. We estimate the
partial width and the branching fraction
, where is an exclusive hadronic channel, and find that
for it may be possible to observe this state in two
photon collisions at CLEO-II.Comment: 9 pages, LATEX forma
The Higgs Boson Might Not Couple To B Quarks
We discuss an alternative version of the electroweak standard model, in which
only the heavy t quark, not the light fermions, couples to the Higgs boson with
a strength given by the standard model. The Higgs particle decays dominantly
into two gluons jets. The branching ratio for the 2 gamma decay is about 3.5%.
The Higgs particle would be a narrow object (width about 60 KeV), and its mass
might be consistent with the value given by typical estimates of radiative
effects measured by the LEP experiments.Comment: 7 pages, 6 figures, to appear in Physics Letters
Flavor changing interactions mediated by scalars at the weak scale
The quark and lepton mass matrices possess approximate flavor symmetries.
Several results follow if the interactions of new scalars possess these
approximate symmetries. Present experimental bounds allow these exotic scalars
to have a weak scale mass. The Glashow-Weinberg criterion is rendered
unnecessary. Finally, rare leptonic B meson decays provide powerful probes of
these scalars, especially if they are leptoquarks.Comment: 13 pages, report LBL-3234
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