197447636
Interpreting Near-side Correlations
Recent data from heavy ion collisions at RHIC show strong near-side correlations extending over several units of rapidity. This ridge-like correlation exhibits an abrupt onset with collision centrality. In this talk, I argue that the centrality and beam-energy dependence of these near-angle correlations could provide access to information about the Quark Gluon Plasma phase boundary and the Equation of State of nuclear matter. A beam-energy-scan at RHIC will better reveal the true source of these correlations and should be a high priority at RHIC.
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
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.
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.
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.
121037084
BACKGROUNDS AND THRESHOLD OF XENON10 DARK MATTER EXPERIMENT
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.
119106969
A coherent understanding of low-energy nuclear recoils in liquid xenon
Liquid xenon detectors such as XENON10 and XENON100 obtain a significant fraction of their sensitivity to light (10 GeV) particle dark matter by looking for nuclear recoils of only a few keV, just above the detector threshold. Yet in this energy regime a correct treatment of the detector threshold and resolution remains unclear. The energy dependence of the scintillation yield of liquid xenon for nuclear recoils also bears heavily on detector sensitivity, yet numerous measurements have not succeeded in obtaining concordant results. In this article we show that the ratio of detected ionization to scintillation can be leveraged to constrain the scintillation yield. We also present a rigorous treatment of liquid xenon detector threshold and energy resolution. Notably, the effective energy resolution differs significantly from a simple Poisson distribution. We conclude with a calculation of dark matter exclusion limits, and show that existing data from liquid xenon detectors strongly constrain recent interpretations of light dark matter.
18747581
An early‐time infrared and optical study of the Type Ia Supernova 1998bu in M96
We present first-season infrared (IR) and optical photometry and spectroscopy of the Type Ia Supernova 1998bu in M96. We also report optical polarimetry of this event. SN 1998bu is one of the closest type Ia supernovae of modern times, and the distance of its host galaxy is well determined. We find that SN 1998bu is both photometrically and spectroscopically normal. However, the extinction to this event is unusually high, with A(V) = 1.0 +/- 0.11. We find that SN 1998bu peaked at an intrinsic M-V = -19.37 +/- 0.23. Adopting a distance modulus of 30.25 (Tanvir et al.) and using Phillips et al.'s relations for the Hubble constant, we obtain H-0 = 70.4 +/- 4.3 km s(-1) Mpc(-1). Combination of our IR photometry with those of Jha et al. provides one of the most complete early-phase IR light curves for a SN Ia published so far. In particular, SN 1998bu is the first normal SN Ia for which good pre-t(Bmax) IR coverage has been obtained. It reveals that the J, H and K light curves peak about 5 days earlier than the flux in the B-band curve.
118494907
Importance of upgraded energy reconstruction for direct dark matter searches with liquid xenon detectors
The usual nuclear recoil energy reconstruction employed by liquid xenon dark matter search experiments relies only on the primary scintillation photon signal. Energy reconstruction based on both the photon and electron signals yields a more accurate representation of search results. For a dark matter particle mass m~10 GeV, a nuclear recoil from a scattering event is more likely to be observed in the lower left corner of the typical search box, rather than near the nuclear recoil calibration centroid. In this region of the search box, the actual nuclear recoil energies are smaller than the usual energy scale suggests, by about a factor x2. Recent search results from the XENON100 experiment are discussed in light of these considerations.