351 research outputs found
Exact SU(2)*U(1) Stringy Black Holes
Extreme magnetic dilaton black holes are promoted to exact solutions of
heterotic string theory with unbroken supersymmetry. With account taken of
alpha' corrections this is accomplished by supplementing the known solutions
with SU(2) Yang-Mills vectors and scalars in addition to the already existing
Abelian U(1) vector field. The solution has a simple analytic form and includes
multi-black-holes. The issue of exactness of other black-hole-type solutions,
including extreme dilaton electrically charged black holes and Taub-NUT
solutions is discussed.Comment: 10 pages, SU-ITP-94-27 and QMW-PH-94-34 (version accepted for
publication in Phys. Rev., contains a discussion of (4.1) supersymmetry of
the black hole sigma model
Demonstration of the temporal matter-wave Talbot effect for trapped matter waves
We demonstrate the temporal Talbot effect for trapped matter waves using
ultracold atoms in an optical lattice. We investigate the phase evolution of an
array of essentially non-interacting matter waves and observe matter-wave
collapse and revival in the form of a Talbot interference pattern. By using
long expansion times, we image momentum space with sub-recoil resolution,
allowing us to observe fractional Talbot fringes up to 10th order.Comment: 17 pages, 7 figure
Azimuthal anisotropy at RHIC: the first and fourth harmonics
We report the first observations of the first harmonic (directed flow, v_1),
and the fourth harmonic (v_4), in the azimuthal distribution of particles with
respect to the reaction plane in Au+Au collisions at the Relativistic Heavy Ion
Collider (RHIC). Both measurements were done taking advantage of the large
elliptic flow (v_2) generated at RHIC. From the correlation of v_2 with v_1 it
is determined that v_2 is positive, or {\it in-plane}. The integrated v_4 is
about a factor of 10 smaller than v_2. For the sixth (v_6) and eighth (v_8)
harmonics upper limits on the magnitudes are reported.Comment: 6 pages with 3 figures, as accepted for Phys. Rev. Letters The data
tables are at
http://www.star.bnl.gov/central/publications/pubDetail.php?id=3
The Fluorescence Detector of the Pierre Auger Observatory
The Pierre Auger Observatory is a hybrid detector for ultra-high energy
cosmic rays. It combines a surface array to measure secondary particles at
ground level together with a fluorescence detector to measure the development
of air showers in the atmosphere above the array. The fluorescence detector
comprises 24 large telescopes specialized for measuring the nitrogen
fluorescence caused by charged particles of cosmic ray air showers. In this
paper we describe the components of the fluorescence detector including its
optical system, the design of the camera, the electronics, and the systems for
relative and absolute calibration. We also discuss the operation and the
monitoring of the detector. Finally, we evaluate the detector performance and
precision of shower reconstructions.Comment: 53 pages. Submitted to Nuclear Instruments and Methods in Physics
Research Section
A Pre-Landing Assessment of Regolith Properties at the InSight Landing Site
This article discusses relevant physical properties of the regolith at the Mars InSight landing site as understood prior to landing of the spacecraft. InSight will land in the northern lowland plains of Mars, close to the equator, where the regolith is estimated to be ≥3--5 m thick. These investigations of physical properties have relied on data collected from Mars orbital measurements, previously collected lander and rover data, results of studies of data and samples from Apollo lunar missions, laboratory measurements on regolith simulants, and theoretical studies. The investigations include changes in properties with depth and temperature. Mechanical properties investigated include density, grain-size distribution, cohesion, and angle of internal friction. Thermophysical properties include thermal inertia, surface emissivity and albedo, thermal conductivity and diffusivity, and specific heat. Regolith elastic properties not only include parameters that control seismic wave velocities in the immediate vicinity of the Insight lander but also coupling of the lander and other potential noise sources to the InSight broadband seismometer. The related properties include Poisson’s ratio, P- and S-wave velocities, Young’s modulus, and seismic attenuation. Finally, mass diffusivity was investigated to estimate gas movements in the regolith driven by atmospheric pressure changes. Physical properties presented here are all to some degree speculative. However, they form a basis for interpretation of the early data to be returned from the InSight mission.Additional co-authors: Nick Teanby and Sharon Keda
ρ\u3csup\u3e0\u3c/sup\u3e production and possible modification in Au + Au and p + p collisions at √s\u3csub\u3eNN\u3c/sub\u3e = 200 GeV
We report results on ρ(770)0→π+π− production at midrapidity in p+p and peripheral Au+Au collisions at √sNN=200 GeV. This is the first direct measurement of ρ(770)0→π+π− in heavy-ion collisions. The measured ρ0 peak in the invariant mass distribution is shifted by ∼40 MeV/c2 in minimum bias p+p interactions and ∼70 MeV/c2 in peripheral Au+Au collisions. The ρ0 mass shift is dependent on transverse momentum and multiplicity. The modification of the ρ0 meson mass, width, and shape due to phase space and dynamical effects are discussed
Event-wise ⟨p\u3csub\u3et\u3c/sub\u3e⟩ fluctuations in Au-Au collisions at √s\u3csub\u3eNN\u3c/sub\u3e = 130 GeV
We present the first large-acceptance measurement of event-wise mean transverse momentum ⟨pt⟩ fluctuations for Au-Au collisions at nucleon-nucleon center-of-momentum collision energy √sNN = 130 GeV. The observed nonstatistical ⟨pt⟩ fluctuations substantially exceed in magnitude fluctuations expected from the finite number of particles produced in a typical collision. The r.m.s. fractional width excess of the event-wise ⟨pt⟩ distribution is 13.7±0.1(stat) ±1.3(syst)% relative to a statistical reference, for the 15% most-central collisions and for charged hadrons within pseudorapidity range |η|c. The width excess varies smoothly but nonmonotonically with collision centrality and does not display rapid changes with centrality which might indicate the presence of critical fluctuations. The reported ⟨pt⟩ fluctuation excess is qualitatively larger than those observed at lower energies and differs markedly from theoretical expectations. Contributions to ⟨pt⟩ fluctuations from semihard parton scattering in the initial state and dissipation in the bulk colored medium are discussed
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