9,634 research outputs found
Enhancement of Dark Matter Annihilation via Breit-Wigner Resonance
The Breit-Wigner enhancement of the thermally averaged annihilation cross
section is shown to provide a large boost factor when the dark
matter annihilation process nears a narrow resonance. We explicitly demonstrate
the evolution behavior of the Breit-Wigner enhanced as the function
of universe temperature for both the physical and unphysical pole cases. It is
found that both of the cases can lead an enough large boost factor to explain
the recent PAMELA, ATIC and PPB-BETS anomalies. We also calculate the coupling
of annihilation process, which is useful for an appropriate model building to
give the desired dark matter relic density.Comment: 4 pages, 4 figures, references added, accepted for publication in
Physical Review
Searching for Dark Matter Signals in the Left-Right Symmetric Gauge Model with CP Symmetry
We investigate singlet scalar dark matter (DM) candidate in a left-right
symmetric gauge model with two Higgs bidoublets (2HBDM) in which the
stabilization of the DM particle is induced by the discrete symmetries P and
CP. According to the observed DM abundance, we predict the DM direct and
indirect detection cross sections for the DM mass range from 10 GeV to 500 GeV.
We show that the DM indirect detection cross section is not sensitive to the
light Higgs mixing and Yukawa couplings except the resonance regions. The
predicted spin-independent DM-nucleon elastic scattering cross section is found
to be significantly dependent on the above two factors. Our results show that
the future DM direct search experiments can cover the most parts of the allowed
parameter space. The PAMELA antiproton data can only exclude two very narrow
regions in the 2HBDM. It is very difficult to detect the DM direct or indirect
signals in the resonance regions due to the Breit-Wigner resonance effect.Comment: 24 pages, 8 figures. minor changes and a reference added, published
in Phys. Rev.
Multiscale Technicolor and the Zbb-bar Vertex
We estimate the correction to the Zbb-bar vertex arising from the exchanges
of the sideways extended technicolor (ETC) boson and the flavor-diagonal ETC
boson in the multiscale walking technicolor model. The obtained result is too
large to explain the present data. However, if we introduce a new self-
interaction for the top quark to induce the top quark condensate serving as the
origin of the large top quark mass, the corrected R_b=Gamma_b/Gamma_h can be
consistent with the recent LEP data. The corresponding correction to
R_c=Gamma_c/Gamma_h is shown to be negligibly small.Comment: 9-page LaTex fil
Production and decay of the neutral top-pion in high energy colliders
We study the production and decay of the neutral top-pion
predicted by topcolor-assisted technicolor(TC2) theory. Our results show that,
except the dominant decay modes , and , the
can also decay into and modes. It can
be significantly produced at high energy collider(LC) experiments
via the processes and . We further calculate the production cross sections of the
processes and . We find that the signatures of the neutral top-pion
can be detected via these processes.Comment: Latex file, 13 Pages, 6 eps figures. to be published in Phys.Rev.
Reflection matrices for the vertex model
The graded reflection equation is investigated for the
vertex model. We have found four classes of diagonal
solutions and twelve classes of non-diagonal ones. The number of free
parameters for some solutions depends on the number of bosonic and fermionic
degrees of freedom considered.Comment: 30 page
On the transport and thermodynamic properties of quasi-two-dimensional purple bronzes AMoO (A=Na, K)
We report a comparative study of the specific heat, electrical resistivity
and thermal conductivity of the quasi-two-dimensional purple bronzes
NaMoO and KMoO, with special emphasis on
the behavior near their respective charge-density-wave transition temperatures
. The contrasting behavior of both the transport and the thermodynamic
properties near is argued to arise predominantly from the different
levels of intrinsic disorder in the two systems. A significant proportion of
the enhancement of the thermal conductivity above in
NaMoO, and to a lesser extent in KMoO, is
attributed to the emergence of phason excitations.Comment: 8 pages, 6 figures, To appear in Physical Review
Precision determination of absolute neutron flux
A technique for establishing the total neutron rate of a highly-collimated
monochromatic cold neutron beam was demonstrated using a method of an
alpha-gamma counter. The method involves only the counting of measured rates
and is independent of neutron cross sections, decay chain branching ratios, and
neutron beam energy. For the measurement, a target of 10B-enriched boron
carbide totally absorbed the neutrons in a monochromatic beam, and the rate of
absorbed neutrons was determined by counting 478keV gamma rays from neutron
capture on 10B with calibrated high-purity germanium detectors. A second
measurement based on Bragg diffraction from a perfect silicon crystal was
performed to determine the mean de Broglie wavelength of the beam to a
precision of 0.024 %. With these measurements, the detection efficiency of a
neutron monitor based on neutron absorption on 6Li was determined to an overall
uncertainty of 0.058 %. We discuss the principle of the alpha-gamma method and
present details of how the measurement was performed including the systematic
effects. We also describe how this method may be used for applications in
neutron dosimetry and metrology, fundamental neutron physics, and neutron cross
section measurements.Comment: 44 page
Associated production of the charged Higgs boson and single top quark at the LHC
The left-right twin Higgs(LRTH) model predicts the existence of the charged
Higgs . In this paper, we study the production of the charged Higgs
boson with single top quark via the process at the
Large Hadron Collider(LHC). The numerical results show that the
production cross section can reach the level of in the reasonable
parameter space of the LRTH model. We expect that, as long as it is not too
heavy, the possible signatures of the heavy charged Higgs boson
might be detected via the decay mode at the LHC
experiments.Comment: This paper has been withdrawn by the author(s) due to some mistakes
in this pape
- β¦