12,613 research outputs found
A Revisit to Top Quark Forward-Backward Asymmetry
We analyze various models for the top quark forward-backward asymmetry
() at the Tevatron, using the latest CDF measurements on different
s and the total cross section. The axigluon model in Ref. \cite{paul}
has difficulties in explaining the large rapidity dependent asymmetry and mass
dependent asymmetry simultaneously and the parameter space relevant to
is ruled out by the latest dijet search at ATLAS. In contrast to
Ref. \cite{cp}, we demonstrate that the large parameter space in this model
with a flavor symemtry is not ruled out by flavor physics. The
-channel flavor-violating \cite{hitoshi},
\cite{waiyee} and diquark \cite{tim} models all have parameter
regions that satisfy different measurements within 1 .
However, the heavy model which can be marginally consistent with
the total cross section is severely constrained by the Tevatron direct search
of same-sign top quark pair. The diquark model suffers from too large total
cross section and is difficult to fit the invariant mass
distribution. The electroweak precision constraints on the model based on
- mixings is estimated and the result is rather weak (
GeV). Therefore, the heavy model seems to give the best fit for
all the measurements. The model predicts the signal
from production and is 10%-50% of SM at the 7 TeV LHC.
Such resonance can serve as the direct test of the model.Comment: 25 pages, 7 figures, 1 tabl
Characterisation of dispersions within annealed HVOLF thermally sprayed AlSnCu coatings
High velocity oxy-liquid fuel (HVOLF) AlSnCu coatings are characterised following annealing for up to 5 hours at 300°C. A combination of statistical analysis of BSE images and TEM observations demonstrate the decrease in the number of sub-micron and nanoscale Sn particles with annealing, commensurate with a decrease in the coating microhardness. TEM evidence further suggests the coarsening of nanoscale Sn through a mechanism of a liquid phase migration within the Al matrix. EELS and EFTEM additionally allow the identification of the precipitation of theta'
Eigenstates of Paraparticle Creation Operators
Eigenstates of the parabose and parafermi creation operators are constructed.
In the Dirac contour representation, the parabose eigenstates correspond to the
dual vectors of the parabose coherent states. In order , conserved-charge
parabose creation operator eigenstates are also constructed. The contour forms
of the associated resolutions of unity are obtained.Comment: 14 pages, LaTex file, no macros, no figure
Electroweak Beautygenesis: From b {\to} s CP-violation to the Cosmic Baryon Asymmetry
We address the possibility that CP-violation in mixing may
help explain the origin of the cosmic baryon asymmetry. We propose a new
baryogenesis mechanism - "Electroweak Beautygenesis" - explicitly showing that
these two CP-violating phenomena can be sourced by a common CP-phase. As an
illustration, we work in the Two-Higgs-Doublet model. Because the relevant
CP-phase is flavor off-diagonal, this mechanism is less severely constrained by
null results of electric dipole moment searches than other scenarios. We show
how measurements of flavor observables by the D0, CDF, and LHCb collaborations
test this scenario.Comment: 4 pages, 1 figure, 1 tabl
Quantum entropy of the Kerr black hole arising from gravitational perturbation
The quantum entropy of the Kerr black hole arising from gravitational
perturbation is investigated by using Null tetrad and \'t Hooft\'s brick-wall
model. It is shown that effect of the graviton\'s spins on the subleading
correction is dependent of the square of the spins and the angular momentum per
unit mass of the black hole, and contribution of the logarithmic term to the
entropy will be positive, zero, and negative for different value of .Comment: 8 pages, 1 figure, Latex. to appear in Phys. Rev.
Statistical Entropy of a Stationary Dilaton Black Hole from Cardy Formula
With Carlip's boundary conditions, a standard Virasoro subalgebra with
corresponding central charge for stationary dilaton black hole obtained in the
low-energy effective field theory describing string is constructed at a Killing
horizon. The statistical entropy of stationary dilaton black hole yielded by
standard Cardy formula agree with its Bekenstein-Hawking entropy only if we
take period of function as the periodicity of the Euclidean black
hole. On the other hand, if we consider first-order quantum correction then the
entropy contains a logarithmic term with a factor , which is different
from Kaul and Majumdar's one, . We also show that the discrepancy is
not just for the dilaton black hole, but for any one whose corresponding
central change takes the form .Comment: 11 pages, no figure, RevTex. Accepted for publication in Phys. Rev.
Entropies of Rotating Charged Black Holes from Conformal Field Theory at Killing Horizons
The covariant phase technique is used to compute the constraint algebra of
the stationary axisymmetric charged black hole. A standard Virasoro subalgebra
with corresponding central charge is constructed at a Killing horizon with
Carlip's boundary conditions. For the Kerr-Newman black hole and the
Kerr-Newman-AdS black hole, the density of states determined by conformal
fields theory methods yields the statistical entropy which agrees with the
Bekenstein-Hawking entropy.Comment: 12 pages, no figure, RevTe
Symmetry of Dirac Equation and Corresponding Phenomenology
It has been suggested that the high symmetries in the Schr\"odinger equation
with the Coulomb or harmonic oscillator potentials may remain in the
corresponding relativistic Dirac equation. If the principle is correct, in the
Dirac equation the potential should have a form as
where is for hydrogen atom and for harmonic
oscillator. However, in the case of hydrogen atom, by this combination the
spin-orbit coupling term would not exist and it is inconsistent with the
observational spectra of hydrogen atom, so that the symmetry of SO(4) must
reduce into SU(2). The governing mechanisms QED and QCD which induce potential
are vector-like theories, so at the leading order only vector potential exists.
However, the higher order effects may cause a scalar fraction. In this work, we
show that for QED, the symmetry restoration is very small and some discussions
on the symmetry breaking are made. At the end, we briefly discuss the QCD case
and indicate that the situation for QCD is much more complicated and
interesting.Comment: 15pages, 3 figures, accepted by International Journal of Modern
Physics
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