218 research outputs found
A Note On T, Topologies
Let t be a T. topology for a set X. The problem of representing t as the lattice product (intersection) of stronger topologies is considered. © 1974 American Mathematical Society
Low-threshold analysis of CDMS shallow-site data
Data taken during the final shallow-site run of the first tower of the
Cryogenic Dark Matter Search (CDMS II) detectors have been reanalyzed with
improved sensitivity to small energy depositions. Four ~224 g germanium and two
~105 g silicon detectors were operated at the Stanford Underground Facility
(SUF) between December 2001 and June 2002, yielding 118 live days of raw
exposure. Three of the germanium and both silicon detectors were analyzed with
a new low-threshold technique, making it possible to lower the germanium and
silicon analysis thresholds down to the actual trigger thresholds of ~1 keV and
~2 keV, respectively. Limits on the spin-independent cross section for weakly
interacting massive particles (WIMPs) to elastically scatter from nuclei based
on these data exclude interesting parameter space for WIMPs with masses below 9
GeV/c^2. Under standard halo assumptions, these data partially exclude
parameter space favored by interpretations of the DAMA/LIBRA and CoGeNT
experiments' data as WIMP signals, and exclude new parameter space for WIMP
masses between 3 GeV/c^2 and 4 GeV/c^2.Comment: 18 pages, 12 figures, 5 table
Exclusion Limits on the WIMP-Nucleon Cross-Section from the First Run of the Cryogenic Dark Matter Search in the Soudan Underground Lab
The Cryogenic Dark Matter Search (CDMS-II) employs low-temperature Ge and Si
detectors to seek Weakly Interacting Massive Particles (WIMPs) via their
elastic scattering interactions with nuclei. Simultaneous measurements of both
ionization and phonon energy provide discrimination against interactions of
background particles. For recoil energies above 10 keV, events due to
background photons are rejected with >99.99% efficiency. Electromagnetic events
very near the detector surface can mimic nuclear recoils because of reduced
charge collection, but these surface events are rejected with >96% efficiency
by using additional information from the phonon pulse shape. Efficient use of
active and passive shielding, combined with the the 2090 m.w.e. overburden at
the experimental site in the Soudan mine, makes the background from neutrons
negligible for this first exposure. All cuts are determined in a blind manner
from in situ calibrations with external radioactive sources without any prior
knowledge of the event distribution in the signal region. Resulting
efficiencies are known to ~10%. A single event with a recoil of 64 keV passes
all of the cuts and is consistent with the expected misidentification rate of
surface-electron recoils. Under the assumptions for a standard dark matter
halo, these data exclude previously unexplored parameter space for both
spin-independent and spin-dependent WIMP-nucleon elastic scattering. The
resulting limit on the spin-independent WIMP-nucleon elastic-scattering
cross-section has a minimum of 4x10^-43 cm^2 at a WIMP mass of 60 GeV/c^2. The
minimum of the limit for the spin-dependent WIMP-neutron elastic-scattering
cross-section is 2x10^-37 cm^2 at a WIMP mass of 50 GeV/c^2.Comment: 37 pages, 42 figure
New Results from the Cryogenic Dark Matter Search Experiment
Using improved Ge and Si detectors, better neutron shielding, and increased
counting time, the Cryogenic Dark Matter Search (CDMS) experiment has obtained
stricter limits on the cross section of weakly interacting massive particles
(WIMPs) elastically scattering from nuclei. Increased discrimination against
electromagnetic backgrounds and reduction of neutron flux confirm
WIMP-candidate events previously detected by CDMS were consistent with neutrons
and give limits on spin-independent WIMP interactions which are >2X lower than
previous CDMS results for high WIMP mass, and which exclude new parameter space
for WIMPs with mass between 8-20 GeV/c^2.Comment: 4 pages, 4 figure
Exclusion limits on the WIMP-nucleon cross-section from the Cryogenic Dark Matter Search
The Cryogenic Dark Matter Search (CDMS) employs low-temperature Ge and Si
detectors to search for Weakly Interacting Massive Particles (WIMPs) via their
elastic-scattering interactions with nuclei while discriminating against
interactions of background particles. For recoil energies above 10 keV, events
due to background photons are rejected with >99.9% efficiency, and surface
events are rejected with >95% efficiency. The estimate of the background due to
neutrons is based primarily on the observation of multiple-scatter events that
should all be neutrons. Data selection is determined primarily by examining
calibration data and vetoed events. Resulting efficiencies should be accurate
to about 10%. Results of CDMS data from 1998 and 1999 with a relaxed
fiducial-volume cut (resulting in 15.8 kg-days exposure on Ge) are consistent
with an earlier analysis with a more restrictive fiducial-volume cut.
Twenty-three WIMP candidate events are observed, but these events are
consistent with a background from neutrons in all ways tested. Resulting limits
on the spin-independent WIMP-nucleon elastic-scattering cross-section exclude
unexplored parameter space for WIMPs with masses between 10-70 GeV c^{-2}.
These limits border, but do not exclude, parameter space allowed by
supersymmetry models and accelerator constraints. Results are compatible with
some regions reported as allowed at 3-sigma by the annual-modulation
measurement of the DAMA collaboration. However, under the assumptions of
standard WIMP interactions and a standard halo, the results are incompatible
with the DAMA most likely value at >99.9% CL, and are incompatible with the
model-independent annual-modulation signal of DAMA at 99.99% CL in the
asymptotic limit.Comment: 40 pages, 49 figures (4 in color), submitted to Phys. Rev. D;
v.2:clarified conclusions, added content and references based on referee's
and readers' comments; v.3: clarified introductory sections, added figure
based on referee's comment
CDMS, Supersymmetry and Extra Dimensions
The CDMS experiment aims to directly detect massive, cold dark matter
particles originating from the Milky Way halo. Charge and lattice excitations
are detected after a particle scatters in a Ge or Si crystal kept at ~30 mK,
allowing to separate nuclear recoils from the dominating electromagnetic
background. The operation of 12 detectors in the Soudan mine for 75 live days
in 2004 delivered no evidence for a signal, yielding stringent limits on dark
matter candidates from supersymmetry and universal extra dimensions. Thirty Ge
and Si detectors are presently installed in the Soudan cryostat, and operating
at base temperature. The run scheduled to start in 2006 is expected to yield a
one order of magnitude increase in dark matter sensitivity.Comment: To be published in the proceedings of the 7th UCLA symposium on
sources and detection of dark matter and dark energy in the universe, Marina
del Rey, Feb 22-24, 200
A Measurement of the Branching Ratio of
We report on a study of the decay carried out as
a part of the KTeV/E799 experiment at Fermilab. The 1997 data yielded a sample
of 1543 events, including an expected background of events. An
effective form factor was determined from the observed distribution of the
invariant mass. Using this form factor in the calculation of the
detector acceptance, the branching ratio was measured to be .Comment: 5 pages, 4 figure
Observation of CP Violation in K(L)->pi+pi-e+e- Decays
We report the first observation of a manifestly CP violating effect in the
K(L)->pi+pi-e+e- decay mode. A large asymmetry was observed in the distribution
of these decays in the CP-odd and T-odd angle phi between the decay planes of
the e+e- and pi+pi- pairs in the K(L) center of mass system. After acceptance
corrections, the overall asymmetry is found to be 13.6+-2.5 (stat) +-1.2
(syst)%. This is the largest CP-violating effect yet observed integrating over
the entire phase space of a mode and the first such effect observed in an
angular variable.Comment: 4 pages 4 figures submitted to pr
First Observation of the decay KL -> pi0 e e gamma
We report on the first observation of the decay KL -> pi0 ee gamma by the
KTeV E799 experiment at Fermilab. Based upon a sample of 48 events with an
estimated background of 3.6 +/- 1.1 events, we measure the KL -> pi0 ee gamma
branching ratio to be (2.34 +/- 0.35 +/- 0.13)x10^{-8}. Our data agree with
recent O(p^6) calculations in chiral perturbation theory that include
contributions from vector meson exchange through the parameter a_V. A fit was
made to the KL -> pi0 ee gamma data for a_V with the result -0.67 +/- 0.21 +/-
0.12, which is consistent with previous results from KTeV.Comment: Submitted to Physical Review Letters, 5 pages, 5 figure
- …