44050071
Closing in on singlet scalar dark matter: LUX, invisible Higgs decays and gamma-ray lines
A bstractWe study the implications of the Higgs discovery and of recent results from dark matter searches on real singlet scalar dark matter. The phenomenology of the model is defined by only two parameters, the singlet scalar mass mS and the quartic coupling a2 between the SU(2) Higgs and the singlet scalar. We concentrate on the window 5 < mS/GeV < 300. The most dramatic impact on the viable parameter space of the model comes from direct dark matter searches with LUX, and, for very low masses in the few GeV range, from constraints from the invisible decay width of the Higgs. In the resonant region the best constraints come from gamma-ray line searches. We show that they leave only a small region of viable parameter space, for dark matter masses within a few percent of half the mass of the Higgs. We demonstrate that direct and indirect dark matter searches (especially the search for monochromatic gamma-ray lines) will play a key role in closing the residual parameter space in the near future.
119270902
A new equation of state for dark energy model
A new parameterization for the dark energy equation of state(EoS) is proposed and some of its cosmological consequences are also investigated. This new parameterization is the modification of Efstathiou' dark energy EoS parameterization. w(z) is a well behaved function for z >> 1 and has same behavior in z at low redshifts with Efstathiou' parameterization. In this parameterization there are two free parameter w(0) and w(a). We discuss the constraints on this model's parameters from current observational data. The best fit values of the cosmological parameters with la confidence-level regions are: Omega(m) = 0.2735(-0.0163)(+0.0171) w(0) = -1.0537(-0.1511)(+0.1432) and w(a) = 0.2738(-0.8288)(+0.8018).
85553258
CONSTRAINING THE DISTRIBUTION OF DARK MATTER IN THE INNER GALAXY WITH AN INDIRECT DETECTION SIGNAL: THE CASE OF A TENTATIVE 130 GeV {gamma}-RAY LINE
Dark matter distribution in the very inner region of our Galaxy is still debated. In N-body simulations, a cuspy dark matter halo density profile is favored. Several dissipative baryonic processes, however, are found to be able to significantly flatten dark matter distribution, and a cored dark matter halo density profile is possible. Baryons dominate the gravitational potential in the inner Galaxy, hence a direct constraint on the abundance of dark matter particles is rather challenging. Recently, a few groups have identified a tentative 130 GeV line signal in the Galactic center, which could be interpreted as the signal of dark matter annihilation. Using current 130 GeV line data and adopting the generalized Navarro-Frenk-White profile of the dark matter halo-local dark matter density rho(0) = 0.4 GeV cm(-3) and r(s) = 20 kpc-we obtain a 95% confidence level lower (upper) limit on the inner slope of dark matter density distribution, alpha = 1.06 (the cross section of dark matter annihilation into gamma-rays (xx -> gamma gamma) = 1.3 x 10(-27) cm(3) s(-1)). Such a slope is consistent with the results of some N-body simulations and, if the signal is due to dark matter, suggests that baryonic processes may be unimportant.
18220605
Thermal Equilibration and Ellipsoidal Expansion of Rotationally-Symmetrical Longitudinal Flow in Relativistc Heavy Ion Collisions
A rotationally-symmetrical ellipsoidal flow model is proposed for the relativistic heavy-ion collisions and compared with the 14.6 A GeV/c Si-Al and 10.8 A GeV/c Au-Au collision data. The large stopping in the heavier collision system and heavier produced particles is accounted for by using the ellipsoidal flow picture. The central dip in the proton and deuteron rapidity distributions for Si-Al collision are reproduced.
121116255
EMC effect and the distortion of the vacuum in nuclei
Based on the argument that the bag radius of a bounded nucleon is larger than that of a free one due to the change of vacuum property in nucleus, a good fit is obtained for the EMC effect.
14666852
Thermal Freeze-out and Longitudinally Non-uniform Collective Expansion Flow in Relativistic Heavy Ion Collisions
The non-uniform longitudinal flow model (NUFM) propsed recently is extended to include also transverse flow. The resulting longitudinally non-uniform collective expansion model (NUCEM) is applied to the calculation of rapidity distribution of kaons, lambdas and protons in relativistic heavy ion collisions at CERN-SPS energies. The model results are compared with the 200 A GeV/$c$ S-S and 158 A GeV/$c$ Pb-Pb collision data. The central dips observed in experiments are reproduced in a natural way.