15479457
Resonance decay effects on anisotropy parameters
We present the elliptic flow v{sub 2} of pions produced from resonance decays. The transverse momentum p{sub T} spectra of the parent particles are taken from thermal model fits and their v{sub 2} are fit under the assumption that they follow a number-of-constituent-quark (NCQ) scaling law expected from quark-coalescence models. The v{sub 2} of pions from resonance particle decays is found to be similar to the measured pion v{sub 2}. We also propose the measurement of electron v{sub 2} as a means to extract open-charm v{sub 2} and investigate whether a thermalized system of quasi-free quarks and gluons (a quark-gluon plasma) is created in collisions of Au nuclei at RHIC.
8293894
Particle dependence of elliptic flow in Au + Au collisions at s(NN)**(1/2) = 200-GeV
The elliptic flow parameter (v 2 ) for K 0 S and Λ+Λ has been measured at mid-rapidity in Au+Au collisions at √s NN = 200 GeV by the STAR Collaboration. The υ 2 values for both K 0 S and Λ+Λ saturate at moderate p T , deviating from the hydrodynamic behaviour observed in the lower p T region. The saturated v 2 values and the p T scales where the deviation begins are particle dependent. The particle-type dependence of v 2 shows features expected from the hadronization of a partonic ellipsoid by coalescence of co-moving quarks. These results will be discussed in relation to the nuclear modification factor (R CP ) which has also been measured for K 0 S and Λ+Λ by the STAR Collaboration.
17939619
RHIC CRITICAL POINT SEARCH: ASSESSING STARs CAPABILITIES.
In this report we discuss the capabilities and limitations of the STAR detector to search for signatures of the QCD critical point in a low energy scan at RHIC. We find that a RHIC low energy scan will cover a broad region of interest in the nuclear matter phase diagram and that the STAR detector--a detector designed to measure the quantities that will be of interest in this search--will provide new observables and improve on previous measurements in this energy range.
118502088
The Sound of the Little Bangs
Measurements of particles emitted from collisions of heavy ions at relativistic energies show evidence for temperature-fluctuations on the freeze-out surface of the expanding fireball. These can be understood as remnants of the density inhomogeneities in the initial collision overlap region. In this paper we present an analysis of heavy-ion collisions analogous to the analysis of the cosmic microwave background radiation. We use data on transverse momentum correlations to extract a power-spectrum from heavy-ion collisions and use a Glauber model for eccentricity to extract the transfer function needed to produce the observed correlations. We also discuss the acoustic signal, the sound that an observer inside the matter would hear.
119402907
Suppression of nonphotonic electrons from enhancement of charm baryons in heavy ion collisions
In Au+Au collisions at 2<p{sub T}<6 GeV/c baryon production is enhanced compared to p+p collisions. Since charm baryon decays produce electrons less frequently than charm meson decays, the nonphotonic electron spectrum is sensitive to the {lambda}{sub c}/D ratio. In this report we study the dependence of the nonphotonic electron spectrum on the baryon-to-meson ratio for charm hadrons. As an example, we take the {lambda}{sub c}/D ratio to have the same form as the {lambda}/K{sub S}{sup 0} ratio. In this case, even if the total charm quark yield in Au+Au collisions scales with the number of binary nucleon-nucleon collisions (N{sub bin}), the electron spectrum at 2<p{sub T}<5 GeV/c is suppressed by as much as 20% relative to N{sub bin} scaled p+p collisions.
125578392
Azimuthal anisotropy of K0(S) and Lambda + anti-Lambda production at mid-rapidity from Au + Au collisions at S(NN)**(1/2) = 130-GeV
14131974
First direct detection limits on sub-GeV dark matter from XENON10.
The first direct detection limits on dark matter in the MeV to GeV mass range are presented, using XENON10 data. Such light dark matter can scatter with electrons, causing ionization of atoms in a detector target material and leading to single- or few-electron events. We use 15  kg day of data acquired in 2006 to set limits on the dark-matter-electron scattering cross section. The strongest bound is obtained at 100 MeV where σ(e)<3×10(-38)  cm2 at 90% C.L., while dark-matter masses between 20 MeV and 1 GeV are bounded by σ(e)<10(-37)  cm2 at 90% C.L. This analysis provides a first proof of principle that direct detection experiments can be sensitive to dark-matter candidates with masses well below the GeV scale.
46522188
The spin-orbit angles of the transiting exoplanets WASP-1b, WASP-24b, WASP-38b and HAT-P-8b from Rossiter–McLaughlin observations
We present observations of the Rossiter-McLaughlin effect for the transiting exoplanet systems WASP-1, WASP-24, WASP-38 and HAT-P-8, and deduce the orientations of the planetary orbits with respect to the host stars’ rotatio n axes. The planets WASP-24b, WASP-38b and HAT-P-8b appear to move in prograde orbits and be well aligned, having sky-projected spin orbit angles consistent with zero: � = 4:7 ± 4:0 � , � =15 +33 � −43� and� = 9:7 +9.0 � −7.7� , respectively. The host stars have Teff < 6250 K and conform with the trend of cooler stars having low obliquities. WASP-38b is a massive planet on a moderately long period, eccentric orbit so may be expected to have a misaligned orbit given the high obliquities measured in similar systems. However, we find no evidence for a large spinorbit angle. By contrast, WASP-1b joins the growing number of misaligned systems and has an almost polar orbit, � = 79:0 +4.5 � −4.3� . It is neither very massive, eccentric nor orbiting a hot host star, and therefore does not share the properties of many other misaligned systems.
123170953
An Investigation of the Infrared Behaviour of the Gluon Propagator in the Axial Gauge
In the axial gauge an integral equation for the gluon propagator of a pure Yang-Mills theory is derived based on the Dyson-Schwinger equation and the Slavnov-Taylor identities. Dimensional regularization is used. The solution of this equation is investigated in the case where the variable γ = (nk)2/n2k2 is different from zero and it is seen that the nice properties of the confining solution D(k) ~ 1/k4 are lost in this case.
120475304
An eikonal line-integral model and factorization in QCD
We study an approximation to perturbative QCD in which all quarks (active and spectator) move along eikonal lines. These eikonal lines are described by matrix operatorsU defined by time-ordered and path-ordered integrals. All known examples of Bloch-Nordsieck cancellations follow simply from the unitary properties ofU. In particular, when the eikonal lines are space-like, the time-ordering can be omitted and the unitarity ofU is evident. In this model, it is possible to examine rather explicitly the soft and very-soft gluons whose effects must cancel if factorization is hold (to leading twist). We can show such cancellation if there is a smooth continuation from space-like eikonal lines to time-like ones. We give some examples relevant to this conjecture, but we are unable to prove it in general.
120972199
Do quarks propagate
Abstract Processes with coloured particles in the initial state are generally infrared divergent. We investigate the effect of this on processes with colourless particles in the initial state, when the amplitude is near an intermediate quark pole. The result is a characteristics logarithmic dependence on the “binding energy” (even though spectator interactions are taken into account), and the result is gauge-invariant. Summed to all orders, the logarithms could perhaps suppress the quark pole.