119180431
Empirical constraints on parton energy loss in nucleus–nucleus collisions at RHIC
Abstract We present empirical features of parton energy loss in nucleus–nucleus collisions at RHIC through studies of the spectra and nuclear modification factors ( R A A ) for charged hadrons, neutral pions ( π 0 ) and non-photonic electrons. The flat distribution of R A A at high transverse momentum ( p T ) for a given collision centrality is consistent with a scenario where parton energy loss Δ p T is proportional to p T . The centrality dependence of the parton energy loss indicates the absence of path length dependence in the magnitude of energy loss. The lack of strong path length dependence suggests a dynamical picture where the dense partonic medium undergoes rapid expansion and the density of the medium falls rapidly in the first a few Fermi interval, which may be much shorter than the full path length. Implications of the empirical constraints on the parton energy loss will also be discussed.
118659719
Statistical and dynamical fluctuations in the ratios of higher cumulants in relativistic heavy ion collisions
With the help of transport and statistical models, we find that the ratios of higher net-proton cumulants measured at RHIC are dominated by the statistical fluctuations. Future measurements should focus on the dynamical fluctuations, which are relevant to the underlying mechanisms of particle production, the critical phenomena in particular. We also demonstrate that a proton-antiproton correlation directly show if protons and antiprotons are emitted independently.
119068540
Spherical-Harmonic Expansion Solution of Classical Transport Equations of Quark
The spherical-harmonic method of solving classical transport equation of quark is investigated. The hydrodynamics description of QGP as well as the relation between diffusion approximation and collective flow in nuclear collisions are discussed.
14494427
Highlights from STAR: probing the early medium in heavy ion collisions
Abstract We present highlights of recent results from the STAR Collaboration at RHIC, focusing on the properties of the early medium created in heavy ion collisions. We emphasize the strangeness production including the observation of a hypernucleus (the hypertriton), the observation of reaction-plane-dependent angular correlation of charged particles searching for local strong parity violation effects in heavy ion collisions, and the evaluation of the medium viscosity from measurements of elliptic flow. We discuss STAR's plan for the “Critical Point Search” program at RHIC.
17737818
Non-photonic electron–hadron correlations at STAR
We present STAR's measurements of azimuthal correlations between non-photonic electrons and charged hadrons in p+p, Cu+Cu and Au+Au collisions at GeV. In p+p collisions, from the non-photonic e?h correlation we have extracted the relative B meson semi-leptonic decay contributions to non-photonic electrons up to electron pt ~ 9 GeV/c. In central Cu+Cu and Au+Au collisions where a dense medium is created, we find that the e?h correlation on the away side of the trigger non-photonic electron has been modified in comparison with the expectation from PYTHIA simulations.
11542069
Observation of a critical gradient threshold for electron temperature fluctuations in the DIII-D Tokamak.
A critical gradient threshold has been observed for the first time in a systematic, controlled experiment for a locally measured turbulent quantity in the core of a confined high-temperature plasma. In an experiment in the DIII-D tokamak where L(T(e))(-1) = |∇T(e)|/T(e) and toroidal rotation were varied, long wavelength (k(θ)ρ(s) ≲ 0.4) electron temperature fluctuations exhibit a threshold in L(T(e))(-1): below, they change little; above, they steadily increase. The increase in δT(e)/T(e) is concurrent with increased electron heat flux and transport stiffness. Observations were insensitive to rotation. Accumulated evidence strongly enforces the identification of the experimentally observed threshold with ∇T(e)-driven trapped electron mode turbulence.
119398656
The Instantaneous formulations for Bethe Salpeter equation and radiative transitions between two bound states
The instantaneous formulations for the relativistic Bethe-Salpeter (BS) and the radiative transitions between the bound-states are achieved if the BS kernel is instantaneous. It is shown that the original Salpeter instantaneous equation set up on the BS equation with an instantaneous kernel should be extended to involve the `small (negative energy) component' of the BS wave functions. As a precise example of the extension for the bound states with one kind of quantum number, the way to reduce the novel extended instantaneous equation is presented. How to guarantee the gauge invariance for the radiative transitions which is formulated in terms of BS wave functions, especially, which is formulated in the instantaneous formulation, is shown. It is also shown that to `guarantee' the gauge invariance for the radiative transitions in instantaneous formulation, the novel instantaneous equation for the bound states plays a very important role. Prospects on the applications and consequences of the obtained instantaneous formulations are outlined.
96428988
On the transverse momentum distribution of strange hadrons produced in relativistic heavy ion collisions
Particles with strange quark content produced in the system 1.93A·GeV58Ni on58Ni have been investigated at GSI Darmstadt with the FOPI detector system. The correlation of these produced particles was analyzed with respect to the reaction plane.Λ baryons exhibit a very pronounced sideward flow pattern which is qualitatively similar to the proton flow. However, the kaon (K+,Ks0) flow patterns are significantly different from that of the protons, and their form may be useful to restrict theoretical models on the form of the kaon potential in the nuclear medium.
117632548
Studies of beam dynamics for eRHIC
We present our studies on various aspects of the beam dynamics in 'racetrack' design of the first stage electron-ion collider at RHIC (eRHIC), including transverse beam break up instabilities, energy loss due to wakefields, electron beam emittance growth and energy loss due to synchrotron radiation, electron beam losses due to Touschek effects and residue gas scattering, beam-beam effects at the interaction region and emittance growth of ion beam due to electron bunch to bunch noises. For all effects considered above, no showstopper has been found.
122315733
Coordinates problem of Hawking radiation derivation in a Kerr–Newman black hole using Hamilton–Jacobi equation
Hawking radiation from a Kerr–Newman black hole is investigated using Hamilton–Jacobi method more deeply. A direct computation will lead to a wrong result via Hamilton–Jacobi method. However, when the well-behaved Painleve coordinate system and Eddington coordinate system are considered, we can get the correct result. The reason of the discrepancy between naive coordinate and well-behaved coordinates is also discussed.
54685450
NSLS-II Injection Straight Diagnostics
The ultra-bright light source being developed by the NSLS-II project will utilize top-up injection and fine tuning of the injection process is mandatory. In this paper we present the diagnostics installed in the injection straight. Its use for commissioning and tuning of the injection cycle is also described. The NSLS-II storage ring will utilize a 9.3 meter long injection straight section shown in Fig. 1. Injection will be preformed with two septa (one pulsed, one DC) and four kickers. The stored beam will be shifted towards the pulsed septum up to IS mm and the nominal distance between centers of the injected and the bumped beam is 9.5mm. The NSLS-II beam position monitors will have turn-by-turn and first-turn capabilities and will be used for the commissioning and tuning the injection process. However, there are three additional BPMs and two beam intercepting OTR screens (flags) installed in the injection straight.