119719187
Dark Matter in Light of the LUX Results
The landscape of dark matter direct detection has been profoundly altered by the slew of recent experiments. While some have claimed signals consistent with dark matter, others have seen few, if any, events consistent with dark matter. The results of the putative detections are often incompatible with each other in the context of naive spin-independent scattering, as well as with the null results. In particular, in light of the conflicts between the DM interpretation of the three events recently reported by the CDMS-Si experiment and the first results of the LUX experiment, there is a strong need to revisit the assumptions that go into the DM interpretations of both signals and limits. We attempt to reexamine a number of particle physics, astrophysics and experimental uncertainties. Specifically, we examine exothermic scattering, isospin-dependent couplings, modified halo models through astrophysics independent techniques, and variations in the assumptions about the scintillation light in liquid Xenon. We find that only a highly tuned isospin-dependent scenario remains as a viable explanation of the claimed detections, unless the scintillation properties of LXe are dramatically different from the assumptions used by the LUX experiment.
121037084
BACKGROUNDS AND THRESHOLD OF XENON10 DARK MATTER EXPERIMENT
119186611
Anisotropic diffusion of electrons in liquid xenon with application to improving the sensitivity of direct dark matter searches
Electron diffusion in a liquid xenon time projection chamber has recently been used to infer the z coordinate of a particle interaction, from the width of the electron signal. The goal of this technique is to reduce the background event rate by discriminating edge events from bulk events. Analyses of dark matter search data which employ it would benefit from increased longitudinal electron diffusion. We show that a significant increase is expected if the applied electric field is decreased. This observation is trivial to implement but runs contrary to conventional wisdom and practice. We also extract a first measurement of the longitudinal diffusion coefficient, and confirm the expectation that electron diffusion in liquid xenon is highly anisotropic under typical operating conditions.
119255314
Azimuthal anisotropy in U+U collisions at STAR
Abstract The azimuthal anisotropy of particle production is commonly used in high-energy nuclear collisions to study the early evolution of the expanding system. The prolate shape of uranium nuclei makes it possible to study how the geometry of the colliding nuclei affects final state anisotropies. It also provides a unique opportunity to understand how entropy is produced in heavy-ion collisions. In this paper, the two- and four-particle cumulant v 2 ( v 2 { 2 } and v 2 { 4 } ) from U+U collisions at s NN = 193 GeV and Au+Au collisions at s NN = 200 GeV for inclusive charged hadrons will be presented. The STAR Zero Degree Calorimeters are used to select very central collisions. Differences were observed between the multiplicity dependence of v 2 { 2 } for most central Au+Au and U+U collisions. The multiplicity dependence of v 2 { 2 } in central collisions was compared to Monte Carlo Glauber model predictions and it was seen that this model cannot explain the present results.
118574179
Beam energy dependence of Elliptic and Triangular flow with the AMPT model
Abstract A beam energy scan has been carried out at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory to search for the onset of deconfinement and a possible critical point where the transition from a Quark Gluon Plasma to a hadronic phase changes from a rapid cross-over to a first order phase transition. Anisotropy in the azimuthal distribution of produced particles such as the second and third harmonics v 2 and v 3 are expected to be sensitive to the existence of a Quark Gluon Plasma phase and the Equation of State of the system. For this reason, they are of great experimental interests. In this Letter we report on calculations of v 2 and v 3 from the AMPT model in the Default (Def.) and String Melting (SM) mode to provide a reference for the energy dependence of v 2 and v 3 for s NN from 7.7 GeV to 2.76 TeV. We expect that in the case that collisions cease to produce QGP at lower colliding energies, data will deviate from the AMPT String Melting calculations and come in better agreement with the Default calculations.
12143325
Constraints on Jupiters from observations of Galactic Bulge microlensing events during 2000.
We present observations of 8 Galactic Bulge microlensing events taken with the 1.0m JKT on La Palma during 2000 June and July. The JKT observing schedule was optimized using a prioritizing algorithm to automatically update the target list. For most of these events we have sampled the lightcurves at times where no information was available from the OGLE alert team. We assume a point-source point-lens (PSPL) model and perform a maximum likelihood fit to both our data and the OGLE data to constrain the event parameters of the fit. We then refit the data assuming a binary lens and proceed to calculate the probability of detecting planets with mass ratio q = 10 3 . We have seen no clear signatures of planetary deviations on any of the 8 events and we quantify constraints on the presence of planetary companions to the lensing stars. For two well observed events, 2000BUL31 and 2000BUL33, our detection probabilities
17495479
Identified Particle Measurements at RHIC: Elucidating Hadronization Mechanisms for Bulk Partonic Matter
Measurements of identified particle momentum spectra at √{sNN} = 200 GeV are reviewed. Emphasis is placed on the azimuthal dependence and the centrality dependence of hadron yields at intermediate transverse momentum (1.5 < pT < 5 GeV/c). The first measurements of the fourth harmonic term (v4) in the azimuthal variation of identified particle yields are shown. The recombination mechanism of hadron formation provides a consistent description of the dependence of these measurements on particle-type.
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.