47 research outputs found
Mobility of thorium ions in liquid xenon
We present a measurement of the Th ion mobility in LXe at 163.0 K and
0.9 bar. The result obtained, 0.2400.011 (stat) 0.011 (syst)
cm/(kV-s), is compared with a popular model of ion transport.Comment: 6.5 pages,
Systematic study of trace radioactive impurities in candidate construction materials for EXO-200
The Enriched Xenon Observatory (EXO) will search for double beta decays of
136Xe. We report the results of a systematic study of trace concentrations of
radioactive impurities in a wide range of raw materials and finished parts
considered for use in the construction of EXO-200, the first stage of the EXO
experimental program. Analysis techniques employed, and described here, include
direct gamma counting, alpha counting, neutron activation analysis, and
high-sensitivity mass spectrometry.Comment: 32 pages, 6 figures. Expanded introduction, added missing table
entry. Accepted for publication in Nucl. Instrum. Meth.
A liquid xenon ionization chamber in an all-fluoropolymer vessel
A novel technique has been developed to build vessels for liquid xenon
ionization detectors entirely out of ultra-clean fluoropolymer. We describe the
advantages in terms of low radioactivity contamination, provide some details of
the construction techniques, and show the energy resolution achieved with a
prototype all-fluoropolymer ionization detector.Comment: 12 pages, 9 figure
Measurement of the Charged Multiplicities in b, c and Light Quark Events from Z0 Decays
Average charged multiplicities have been measured separately in , and
light quark () events from decays measured in the SLD experiment.
Impact parameters of charged tracks were used to select enriched samples of
and light quark events, and reconstructed charmed mesons were used to select
quark events. We measured the charged multiplicities:
,
, from
which we derived the differences between the total average charged
multiplicities of or quark events and light quark events: and . We compared
these measurements with those at lower center-of-mass energies and with
perturbative QCD predictions. These combined results are in agreement with the
QCD expectations and disfavor the hypothesis of flavor-independent
fragmentation.Comment: 19 pages LaTex, 4 EPS figures, to appear in Physics Letters
Characterization of large area APDs for the EXO-200 detector
EXO-200 uses 468 large area avalanche photodiodes (LAAPDs) for detection of
scintillation light in an ultra-low-background liquid xenon (LXe) detector. We
describe initial measurements of dark noise, gain and response to xenon
scintillation light of LAAPDs at temperatures from room temperature to 169K -
the temperature of liquid xenon. We also describe the individual
characterization of more than 800 LAAPDs for selective installation in the
EXO-200 detector.Comment: 10 pages, 17 figure
Search for Neutrinoless Double- β Decay with the Complete EXO-200 Dataset
A search for neutrinoless double-β decay (0νββ) in Xe136 is performed with the full EXO-200 dataset using a deep neural network to discriminate between 0νββ and background events. Relative to previous analyses, the signal detection efficiency has been raised from 80.8% to 96.4±3.0%, and the energy resolution of the detector at the Q value of Xe136 0νββ has been improved from σ/E=1.23% to 1.15±0.02% with the upgraded detector. Accounting for the new data, the median 90% confidence level 0νββ half-life sensitivity for this analysis is 5.0×1025 yr with a total Xe136 exposure of 234.1 kg yr. No statistically significant evidence for 0νββ is observed, leading to a lower limit on the 0νββ half-life of 3.5×1025 yr at the 90% confidence level
Performance of novel VUV-sensitive Silicon Photo-Multipliers for nEXO
Liquid xenon time projection chambers are promising detectors to search for
neutrinoless double beta decay (0), due to their response
uniformity, monolithic sensitive volume, scalability to large target masses,
and suitability for extremely low background operations. The nEXO collaboration
has designed a tonne-scale time projection chamber that aims to search for
0 of \ce{^{136}Xe} with projected half-life sensitivity of
~yr. To reach this sensitivity, the design goal for nEXO is
1\% energy resolution at the decay -value (~keV).
Reaching this resolution requires the efficient collection of both the
ionization and scintillation produced in the detector. The nEXO design employs
Silicon Photo-Multipliers (SiPMs) to detect the vacuum ultra-violet, 175 nm
scintillation light of liquid xenon. This paper reports on the characterization
of the newest vacuum ultra-violet sensitive Fondazione Bruno Kessler VUVHD3
SiPMs specifically designed for nEXO, as well as new measurements on new test
samples of previously characterised Hamamatsu VUV4 Multi Pixel Photon Counters
(MPPCs). Various SiPM and MPPC parameters, such as dark noise, gain, direct
crosstalk, correlated avalanches and photon detection efficiency were measured
as a function of the applied over voltage and wavelength at liquid xenon
temperature (163~K). The results from this study are used to provide updated
estimates of the achievable energy resolution at the decay -value for the
nEXO design
Search for Neutrinoless Double-Beta Decay with the Upgraded EXO-200 Detector
Results from a search for neutrinoless double-beta decay (0νββ) of Xe136 are presented using the first year of data taken with the upgraded EXO-200 detector. Relative to previous searches by EXO-200, the energy resolution of the
A Combination of Preliminary Electroweak Measurements and Constraints on the Standard Model, 2001: addendum
This note presents a combination of published and preliminary electroweak results from the four LEP collaborations and the SLD collaboration which were prepared for the 2001 summer conferences. Averages from Z resonance results are derived for hadronic and leptonic cross sections, the leptonic forward-backward asymmetries, the tau polarisation asymmetries, the b-bbar and c-cbar partial widths and forward-backward asymmetries and the q-qbar charge asymmetry. Above the Z resonance, averages are derived for di-fermion cross sections and forward-backward asymmetries, W-pair, Z-pair and single-W production cross section, electroweak gauge boson couplings, W mass and width and W decay branching ratios. For the first time, total and differential cross sections for di-photon production are combined. The main changes with respect to the experimental results presented in summer 2000 are updates to the Z-pole heavy flavour results from SLD and LEP and to the W mass from LEP. The results are compared with precise electroweak measurements from other experiments. Using a new evaluation of the hadronic vacuum polarisation, the parameters of the Standard Model are evaluated, first using the combined LEP electroweak measurements, and then using the full set of electroweak results.This note presents a combination of published and preliminary electroweak results from the four LEP collaborations and the SLD collaboration which were prepared for the 2001 summer conferences. Averages from Z resonance results are derived for hadronic and leptonic cross sections, the leptonic forward-backward asymmetries, the tau polarisation asymmetries, the b-bbar and c-cbar partial widths and forward-backward asymmetries and the q-qbar charge asymmetry. Above the Z resonance, averages are derived for di-fermion cross sections and forward-backward asymmetries, W-pair, Z-pair and single-W production cross section, electroweak gauge boson couplings, W mass and width and W decay branching ratios. For the first time, total and differential cross sections for di-photon production are combined. The main changes with respect to the experimental results presented in summer 2000 are updates to the Z-pole heavy flavour results from SLD and LEP and to the W mass from LEP. The results are compared with precise electroweak measurements from other experiments. Using a new evaluation of the hadronic vacuum polarisation, the parameters of the Standard Model are evaluated, first using the combined LEP electroweak measurements, and then using the full set of electroweak results