We present a phenomenological approach (EPOS), based on the parton model, but going much beyond, and try to understand proton-proton and deuteron-gold collisions, in particular the transverse momentum results from all the four RHIC experiments. It turns out that elastic and inelastic parton ladder splitting is the key issue. Elastic splitting is in fact related to screening and saturation, but much more important is the inelastic contribution, being crucial to understand the data. We investigate in detail the rapidity dependence of nuclear effects, which is actually relatively weak in the model, in perfect agreement with the data, if the latter ones are interpreted correctly.

Medium excitation by jet shower propagation inside a quark-gluon plasma is studied within a linear Boltzmann transport and a multiphase transport model. Contrary to the naive expectation, it is the deflection of both the jet shower and the Mach-cone-like excitation in an expanding medium that is found to gives rise to a double-peak azimuthal particle distribution with respect to the initial jet direction. Such deflection is the strongest for hadron-triggered jets which are often produced close to the surface of dense medium due to trigger-bias and travel against or tangential to the radial flow. Without such trigger bias, the effect of deflection on γ-jet showers and their medium excitation is weaker. Comparative study of hadron and γ-triggered particle correlations can therefore reveal the dynamics of jet-induced medium excitation in high-energy heavy-ion collisions.PACS numbers: 25.75.Bh,25.75.Cj,25.75.Ld Strong jet quenching has been observed in experiments [1][2][3][4] at the Relativistic Heavy-ion Collider (RHIC) as a consequence of jet quenching or parton energy loss in high-energy heavy-ion collisions [5]. The energy and momentum lost by a propagating parton will be carried by radiated gluons and recoiled medium partons which in turn will go through further interaction and eventually lead to collective medium excitation such as supersonic waves or Mach cones [6,7]. Indeed, Mach cones have been found in the solutions of both hydrodynamic response [8][9][10][11][12] and linearized Einstein equations in string theory [13,14] excited by a propagating jet. Such collective excitation by a propagating jet is expected to be responsible for the observed conic back-to-back (b2b) azimuthal dihadron [15,16] and trihadron correlations [17] with a maximum opening angle of ∆φ ≈ 1 (rad) relative to the backside of a triggered high-p T hadron. However, hadron spectra from the freeze-out of the Mach cone in both hydrodynamics with realistic energy-momentum deposition by jets [6,9,10] and string calculations in the hydrodynamic regime [14] fail to reproduce the observed conic azimuthal correlations. Such correlations on the other hand are observed in a multiphase transport (AMPT) Monte Carlo simulations [18] which could come from jetinduced wakes that are deflected by a radially expanding medium [10].Dihadrons with a high-p T trigger are mostly dominated by b2b jets that are produced close to the surface of the dense matter [19] with the awayside jets often traveling against or tangential to the radial flow. Deflection of these jet showers and associated Mach cones by the radial flow can lead to double-peaked hadron azimuthal correlations. On the other hand, high-p T γ's are produced throughout the volume of the dense matter [20]. The effect of deflection should be reduced for γ-triggered jet showers after averaging over all possible production positions and propagation direction, leading to a weaker double-hump γ-hadron correlation as compared to dihadron correlation.In this Letter, we will study medium excitation by a...

We investigated the information carried by the data on direct photons, i.e., the transverse momentum spectrum and the elliptic flow v 2 from Pb + Pb collisions at √ s NN = 2.76 TeV measured at the Large Hadron Collider and from Au + Au collisions at √ s NN = 200 GeV measured at the Relativistic Heavy Ion Collider, in the framework of (3 + 1)-dimensional ideal hydrodynamical models constrained with hadronic data. We found that these direct photon data may serve as a useful clock at the early stage of heavy ion collisions. The time scales for reaching thermal and chemical equilibrium, extracted from those data, are about 1/3 and 1.5 fm/c, respectively. Thus the large elliptic flow of direct photons is explainable. High-order harmonics, i.e., v 3 , v 4 , and v 5 , of direct photons from Pb + Pb collisions at 2.76 TeV are also predicted, as a further test to compete with those who claim new sources of photons to account for the large elliptic flow of direct photons.

The transverse momentum (p t ) dependence, the centrality dependence, and the rapidity dependence of the elliptic flow of thermal photons in Au + Au collisions at √ s NN = 200 GeV are predicted on the basis of a three-dimensional ideal hydrodynamic description of the hot and dense matter. The elliptic flow parameter v 2 , i.e., the second Fourier coefficient of azimuthal distribution, of thermal photons first increases with p t and then decreases for p t > 2 GeV/c, because of the weak transverse flow at the early stage. The p t -integrated v 2 first increases with centrality, reaches a maximum at about 50% centrality, and then decreases. The rapidity dependence of the elliptic flow v 2 (y) of direct photons (mainly thermal photons) is very sensitive to the initial energy density distribution along the longitudinal direction, which provides a useful tool to extract the realistic initial condition from measurements.

• ufPWV technique is real-time and well repeatable for assessing carotid stiffness • ufPWV measurements increase and correlate well with age • PWV-ES is a quantitative predictor for the early assessment of AS.