118397778
Search for dark matter signals with Fermi-LAT observation of globular clusters NGC 6388 and M15
The globular clusters are probably good targets for dark matter (DM) searches in gamma-rays due to the possible adiabatic contraction of DM by baryons. In this work we analyse the three-year data collected by Fermi Large Area Telescope of globular clusters NGC 6388 and M 15 to search for possible DM signals. For NGC 6388 the detection of gamma-ray emission was reported by Fermi collaboration, which is consistent with the emission of a population of millisecond pulsars. The spectral shape of NGC 6388 is also shown to be consistent with a DM contribution if assuming the annihilation final state is b (b) over bar. No significant gamma-ray emission from M 15 is observed. We give the upper limits of DM contribution to gamma-ray emission in both NGC 6388 and M 15, for annihilation final states b (b) over bar, W+W-, mu(+)mu(-), tau(+)tau(-) and monochromatic line. The constraints are stronger than that derived from observation of dwarf galaxies by Fermi.
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.
123132096
Observational constraints on the early dark energy model
Dark energy can be studied by its influence on the expansion of the Universe. We investigate current constraints on early dark energy (EDE) achievable by the combined observational data from type Ia supernovae (557), baryon acoustic oscillations, the current cosmic microwave background and the observed Hubble parameter. We find that combining these data sets provides powerful constraints on early dark energy and the best fit values of the parameters in 68% and 95% confidence-level regions are: Omega(m0) = 0.2897(-0.0138-0.0194)(+0.0149+0.0207) Omega(e) = 0.0125(-0.0129-0.0129)(+0.0272+0.0381), omega(0) = -1.0415(-0.109-0.1604)(+0.0891+0.1182), and h = 0.6988(-0.0058-0.0081)(+0.0059+0.0083).
2019917
The Beylkin-Cramer Summation Rule and a New Fast Algorithm of Cosmic Statistics for Large Data Sets
Based on the Beylkin-Cramer summation rule, we introduce a new fast algorithm that enables us to explore the high-order statistics efficiently in large data sets. Central to this technique is to make decompositions both of fields and operators within the framework of multiresolution analysis and to realize their discrete representations. Accordingly, a homogeneous point process could be equivalently described by the operation of a Toeplitz matrix on a vector, which is accomplished by making use of the fast Fourier transformation. The algorithm could be applied widely in cosmic statistics to tackle large data sets. We demonstrate this novel technique using the spherical, cubic, and cylindrical counts in cells. The numerical test shows that the algorithm produces an excellent agreement with the expected results. Moreover, the algorithm naturally introduces a sharp filter, which is capable of suppressing shot noise in weak signals. In the numerical procedures, the algorithm is somewhat similar to particle-mesh methods in N-body simulations. Since it is scaled with O(N log N), it is significantly faster than the current particle-based methods, and its computational cost does not rely on the shape or size of the sampling cells. In addition, based on this technique, we further propose a simple fast scheme to compute the second statistics for cosmic density fields and justify it using simulation samples. Hopefully, the technique developed here allows us to make a comprehensive study of non-Gaussianity of the cosmic fields in high-precision cosmology. A specific implementation of the algorithm is publicly available on request to the author.
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.
120439954
Effects of elliptic flow and resonance decay process on the Kurtosis of net baryon distributions
Kurtosis is regarded as a meaningful and promising observable in searching for the possible critical point predicted by QCD. In this paper, the effects of elliptic flow and resonance decay process on the Kurtosis have been studied with Monte Carlo event generators in Au + Au collisions at GeV. The results show that the Kurtosis is not sensitive to elliptic flow and resonance decay process.