66 research outputs found
Can ICARUS and OPERA \nu_{\tau} appearance experiments detect new flavor physics ?
In this letter we explore whether we have a chance to observe a
flavor-changing effect in appearance experiments ICARUS and OPERA.Comment: 10 pages including 3 eps files. We added the comments on the
variation of the oscillation parameters and revised the discussion on model
Two-Loop Electroweak Heavy-Fermion Corrections to Higgs-Boson Production and Decay
The dominant electroweak corrections to the production cross sections and
partial decay widths of a light Standard-Model Higgs boson, with mass M_H <<
2m_t, are due to top-quark loops. By means of a low-energy theorem, we study at
the two-loop level the leading shifts in the Higgs-boson couplings to pairs of
light fermions and gauge bosons induced by a sequential isodoublet of high-mass
fermions. For tree-level and loop-induced Higgs-boson couplings, these
corrections are of relative orders O(G_mu^2 m_F^4) and O(G_mu m_F^2),
respectively, where m_F represents a generic heavy-fermion mass, with m_F >>
M_W, M_H. Except for the Hbb-bar coupling, all results carry over to the case
of the top-quark-induced corrections. We discuss possible phenomenological
consequences of our results.Comment: 29 pages (Latex), 3 figures (Postscript
Coherence Enhanced Transient Lasing in XUV Regime
We report the effect of a coherent drive on transient lasing in three-level
and configurations (). We
show that the presence of a resonant coherent drive on the
optical transition can yield an order of magnitude enhancement of the output
laser energy on a XUV or X-ray transition than with no
coherent drive. We demonstrate the crucial role of coherence for
the laser power enhancement. Contrary to the forward direction (with respect to
the pump), where forward gain can be enhanced for some choice of the drive Rabi
frequency , coherent drive on the transition always suppresses
the backward gain.Comment: 8 pages, 11 figure
Thermally activated Hall creep of flux lines from a columnar defect
We analyse the thermally activated depinning of an elastic string (line
tension ) governed by Hall dynamics from a columnar defect modelled
as a cylindrical potential well of depth for the case of a small
external force An effective 1D field Hamiltonian is derived in order to
describe the 2D string motion. At high temperatures the decay rate is
proportional to with a constant of order of the
critical force and U(F) \sim{\left ({\epsilon V_{0}})}^{{1}/{2}}{V_{0}/{F}}
the activation energy. The results are applied to vortices pinned by columnar
defects in superclean superconductors.Comment: 12 pages, RevTeX, 2 figures inserte
Turning Points in the Evolution of Isolated Neutron Stars' Magnetic Fields
During the life of isolated neutron stars (NSs) their magnetic field passes
through a variety of evolutionary phases. Depending on its strength and
structure and on the physical state of the NS (e.g. cooling, rotation), the
field looks qualitatively and quantitatively different after each of these
phases. Three of them, the phase of MHD instabilities immediately after NS's
birth, the phase of fallback which may take place hours to months after NS's
birth, and the phase when strong temperature gradients may drive thermoelectric
instabilities, are concentrated in a period lasting from the end of the
proto--NS phase until 100, perhaps 1000 years, when the NS has become almost
isothermal. The further evolution of the magnetic field proceeds in general
inconspicuous since the star is in isolation. However, as soon as the product
of Larmor frequency and electron relaxation time, the so-called magnetization
parameter, locally and/or temporally considerably exceeds unity, phases, also
unstable ones, of dramatic changes of the field structure and magnitude can
appear. An overview is given about that field evolution phases, the outcome of
which makes a qualitative decision regarding the further evolution of the
magnetic field and its host NS.Comment: References updated, typos correcte
Two-Loop O(alpha_s G_F M_Q^2) Heavy-Quark Corrections to the Interactions between Higgs and Intermediate Bosons
By means of a low-energy theorem, we analyze at O(alpha_s G_F M_Q^2) the
shifts in the Standard-Model W^+W^-H and ZZH couplings induced by virtual
high-mass quarks, Q, with M_Q >> M_Z, M_H, which includes the top quark.
Invoking the improved Born approximation, we then find the corresponding
corrections to various four- and five-point Higgs-boson production and decay
processes which involve the W^+W^-H and ZZH vertices with one or both of the
gauge bosons being connected to light-fermion currents, respectively. This
includes e^+e^- -> f anti-f H via Higgs-strahlung, via W^+W^- fusion (with f =
nu_e), and via ZZ fusion (with f = e), as well as H -> 2V -> 4f (with V = W,
Z).Comment: 20 pages (Latex); Physical Review D (to appear
Magnetic Field Amplification in Galaxy Clusters and its Simulation
We review the present theoretical and numerical understanding of magnetic
field amplification in cosmic large-scale structure, on length scales of galaxy
clusters and beyond. Structure formation drives compression and turbulence,
which amplify tiny magnetic seed fields to the microGauss values that are
observed in the intracluster medium. This process is intimately connected to
the properties of turbulence and the microphysics of the intra-cluster medium.
Additional roles are played by merger induced shocks that sweep through the
intra-cluster medium and motions induced by sloshing cool cores. The accurate
simulation of magnetic field amplification in clusters still poses a serious
challenge for simulations of cosmological structure formation. We review the
current literature on cosmological simulations that include magnetic fields and
outline theoretical as well as numerical challenges.Comment: 60 pages, 19 Figure
Two-Loop Electroweak Corrections to the A^0 gamma gamma and A^0 g g Couplings of the CP-Odd Higgs Boson
Using the asymptotic-expansion technique, we compute the dominant two-loop
electroweak corrections, of O(G_F m_t^2), to production and decay via a pair of
photons or gluons of the CP-odd Higgs boson A^0 in a two-Higgs-doublet model
with low- to intermediate values of the Higgs-boson masses and ratio
tan(beta)=v_2/v_1 of the vacuum expectation values. We also study the influence
of a sequential heavy-fermion generation. The appearance of three gamma_5
matrices in closed fermion loops requires special care in the dimensional
regularisation of ultraviolet divergences. The finite renormalisation constant
for the pseudoscalar current effectively restoring the anticommutativity of the
gamma_5 matrix, familiar from perturbative quantum chromodynamics, is found not
to receive a correction in this order. We also revisit the dominant two-loop
electroweak correction to the H -> gamma gamma decay width in the standard
model with a fourth fermion generation.Comment: 27 pages, 11 figure
Dispersion and properties of natural rubber‐montmorillonite nanocomposites fabricated by novel in situ
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