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.
120498489
Elliptic flow in a hadron transport model
We present elliptic flow v2 as a function of freeze-out time, transverse momentum for π, K, nucleon, Λ, Ξ and Ω in Au+Au collisions at within two transport approaches (RQMD and UrQMD). The presence of mass ordering and NCQ scaling in the string-hadron model suggests that hadronic interactions do contribute to the observed particle-type dependence of v2 as well.
118652542
Study of triangular flow v3 in Au+Au and Cu+Cu collisions with a multiphase transport model
We studied the relation between the initial geometry anisotropy and the anisotropic flow in a multiphase transport model for both Au+Au and Cu+Cu collisions at = 200 GeV. It is found that unlike the elliptic flow v2, little centrality dependence of the triangular flow v3 is observed. After removing the initial geometry effect, v3/e3 increases with the transverse particle density, which is similar to v2/e2. The transverse momentum (pT) dependence of v3 from identified particles is qualitatively similar to the pT dependence of v2.
17224426
New results for hadronic collisions in the framework of the Parton-Based Gribov-Regge Theory
Abstract We recently proposed a new approach to high energy nuclear scattering, which treats hadronic collisions in a sophisticated way. Demanding theoretical consistency as a minimal requirement for a realistic model, we provide a solution for the energy conservation, screening problems and identical elementary interactions, the so-called “Parton-Based Gribov-Regge Theory” including enhanced diagrams. We can now present some of our results for SPS and RHIC energies.
15711757
Thermal Equilibrium and Non-uniform Longitudinal Flow in Relativistic Heavy Ion Collisions
A model with non-uniform flow in the longitudinal direction 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 stronger influence of transparency on the distribution of heavier produced particles and the larger stopping in the heavier collision system are accounted for by using a new geometrical parameterization picture. The central dips in the proton and deuteron rapidity distributions for Si-Al collision are reproduced.
1752055
On transverse momentum event–by–event fluctuations in string hadronic models
Abstract. Transverse momentum event–by–event fluctuations are studied within the string–hadronic model of high energy nuclear collisions, LUCIAE. Data on non–statistical $p_T$ fluctuations in p+p interactions are reproduced. Fluctuations of similar magnitude are predicted for nucleus–nucleus collisions, in contradiction to the preliminary NA49 results. The introduction of a string clustering mechanism (Firecracker Model) leads to a further, significant increase of $p_T$ fluctuations for nucleus–nucleus collisions. Secondary hadronic interactions, as implemented in LUCIAE, cause only a small reduction of $p_T$ fluctuations.
118532372
Constraints on ultracompact minihalos from extragalactic {\gamma}-ray background
It has been proposed that ultracompact minihalos (UCMHs) might be formed in earlier epoch. If dark matter consists of Weakly Interacting Massive Particles (WIMPs), UCMHs can be treated as the γ-ray sources due to dark matter annihilation within them. In this paper, we investigate the contributions of UCMHs formed during three phase transitions (i.e., electroweak symmetry breaking, QCD confinement and e+e− annihilation) to the extragalactic γ-ray background. Moreover, we use the Fermi-LAT observation data of the extragalactic γ-ray background to get the constraints on the current abundance of UCMHs produced during these phase transitions. We also compare these results with those obtained from Cosmic Microwave Background (CMB) observations and find that the constraints from the Fermi-LAT are more stringent than those from CMB.
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).
118116548
GeV excess in the Milky Way: Depending on Diffuse Galactic gamma ray Emission template?
University of Chinese Academy of Sciences, Yuquan Road 19, Beijing, 100049, China.(Dated: June 27, 2014)Several groups have analyzed the publicly-available Fermi-LAT data and reported a spatiallyextended gamma rays excess of around 1−3 GeV from the region surrounding the Galactic Centerthat might originate from annihilation of dark matter particles with a rest mass m
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).
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.