190 research outputs found
First results from a second generation galactic axion experiment
We report first results from a large scale search for dark matter axions. The experiment probes axion masses of 1.3-13 micro-eV at a sensitivity which is about 50 times higher than previous pilot experiments. We have already scanned part of this mass range at a sensitivity better than required to see at least one generic axion model, the KSVZ axion. Data taking at full sensitivity commenced in February 1996 and scanning the proposed mass range will require three years
High precision branching ratio measurement for the superallowed β decay of [Formula Presented] A prerequisite for exacting tests of the standard model
Nonanalog Fermi and Gamow-Teller branches in the superallowed β decay of [Formula Presented] have been investigated using γ-ray and conversion-electron spectroscopy. Nine observed transitions, in conjunction with a recent shell model calculation, determine the branching ratio of the analog transition to be 99.5(1)%. The experimental upper limits for the Fermi decay to the [Formula Presented] and [Formula Presented] levels are in agreement with recent theoretical predictions. The [Formula Presented] value for the [Formula Presented] β decay is predicted to be 10405(9) keV. © 2003 The American Physical Society
Multiplicity distribution and spectra of negatively charged hadrons in Au+Au collisions at sqrt(s_nn) = 130 GeV
The minimum bias multiplicity distribution and the transverse momentum and
pseudorapidity distributions for central collisions have been measured for
negative hadrons (h-) in Au+Au interactions at sqrt(s_nn) = 130 GeV. The
multiplicity density at midrapidity for the 5% most central interactions is
dNh-/deta|_{eta = 0} = 280 +- 1(stat)+- 20(syst), an increase per participant
of 38% relative to ppbar collisions at the same energy. The mean transverse
momentum is 0.508 +- 0.012 GeV/c and is larger than in central Pb+Pb collisions
at lower energies. The scaling of the h- yield per participant is a strong
function of pt. The pseudorapidity distribution is almost constant within
|eta|<1.Comment: 6 pages, 3 figure
Fine structure of the Gamow-Teller resonance revealed in the decay of Ho-150 2(-) isomer
The γ rays following the 72s 150Ho 2- Gamow-Teller β decay have been investigated with the CLUSTER CUBE setup, an array of six EUROBALL CLUSTER Ge detectors in close cubic geometry, providing a γ ray detection sensitivity of 2×10-5 per β-parent decay for γ-ray energies up to 5 MeV. The fine structure of the Gamow-Teller resonance at 4.4-MeV excitation in 150Dy has been studied. The resolved levels are compared with Shell Model predictions
Pion Interferometry of GeV Au+Au Collisions at RHIC
Two-pion correlation functions in Au+Au collisions at
GeV have been measured by the STAR (Solenoidal Tracker at RHIC) detector. The
source size extracted by fitting the correlations grows with event multiplicity
and decreases with transverse momentum. Anomalously large sizes or emission
durations, which have been suggested as signals of quark-gluon plasma formation
and rehadronization, are not observed. The HBT parameters display a weak energy
dependence over a broad range in .Comment: 6 pages, 3 figures; accepted to Phys Rev Lett; data tables available
at STAR web site http://www.star.bnl.gov/ Click on "Publications" in menu ba
Antideuteron and antihelion production in root(s) = 130 GeV Au+Au collisions
The first measurements of light antinucleus production in Au+Au collisions at
RHIC are reported. The observed production rates for antideuterons and
antihelions are much larger than in lower energy nucleus-nucleus collisions. A
coalescence model analysis of the yields indicates that there is little or no
increase in the antinucleon freeze-out volume compared to collisions at SPS
energy. These analyses also indicate that the antihelion freeze-out volume is
smaller than the antideuteron freeze-out volume.Comment: Submitted to Phys. Rev. Let
Identified Particle Elliptic Flow in Au+Au Collisions at GeV}
We report first results on elliptic flow of identified particles at
mid-rapidity in Au+Au collisions at GeV using the STAR
TPC at RHIC. The elliptic flow as a function of transverse momentum and
centrality differs significantly for particles of different masses. This
dependence can be accounted for in hydrodynamic models, indicating that the
system created shows a behavior consistent with collective hydrodynamical flow.
The fit to the data with a simple model gives information on the temperature
and flow velocities at freeze-out.Comment: REVTeX style include
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