Many experiments that aim at the direct detection of Dark Matter are able to distinguish a dominant background from the expected feeble signals, based on some measured discrimination parameter. We ...develop a statistical model for such experiments using the Profile Likelihood ratio as a test statistic in a frequentist approach. We take data from calibrations as control measurements for signal and background, and the method allows the inclusion of data from Monte Carlo simulations. Systematic detector uncertainties, such as uncertainties in the energy scale, as well as astrophysical uncertainties, are included in the model. The statistical model can be used to either set an exclusion limit or to make a discovery claim, and the results are derived with a proper treatment of statistical and systematic uncertainties. We apply the model to the first data release of the XENON100 experiment, which allows to extract additional information from the data, and place stronger limits on the spin-independent elastic WIMP-nucleon scattering cross-section. In particular, we derive a single limit, including all relevant systematic uncertainties, with a minimum of 2.4x10^-44 cm^2 for WIMPs with a mass of 50 GeV/c^2.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UM
Two-neutrino double electron capture is a rare nuclear decay where two electrons are simultaneously captured from the atomic shell. For Xe-124 this process has not yet been observed and its detection ...would provide a new reference for nuclear matrix element calculations. We have conducted a search for two-neutrino double electron capture from the K shell of 124Xe using 7636 kg d of data from the XENON100 dark matter detector. Using a Bayesian analysis we observed no significant excess above background, leading to a lower 90% credibility limit on the half-life T-1/2 > 6.5 x 10(20) yr. We have also evaluated the sensitivity of the XENON1T experiment, which is currently being commissioned, and found a sensitivity of T-1/2 > 6.1 x 10(22) yr after an exposure of 2 t yr.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UM
Thin Gap Chamber upgrade for SLHC: Position resolution in a test beam Smakhtin, V.; Mikenberg, G.; Klier, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
2009, 2009-1-00, Volume:
598, Issue:
1
Journal Article
Peer reviewed
The position resolution of two small TGC with different readout strip pitch was measured by 10
GeV/
c pion in PS-T9 test beam in November 2007 at CERN. The position resolutions ranging between 50 and ...150
μm have been obtained up to the largest incident angle of muons in the so-called Small-Wheel region. The worsening of the resolution as a function of angle is expected in this type of wire-chamber detectors, due to the elongation of the avalanche along the wire, however the results achieved satisfy the needs for the SLHC upgrade.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The XENON100 experiment, installed underground at the Laboratori Nazionali del Gran Sasso, aims to directly detect dark matter in the form of weakly interacting massive particles (WIMPs) via their ...elastic scattering off xenon nuclei. This paper presents a study on the nuclear recoil background of the experiment, taking into account neutron backgrounds from (α, n) reactions and spontaneous fission due to natural radioactivity in the detector and shield materials, as well as muon-induced neutrons. Based on Monte Carlo simulations and using measured radioactive contaminations of all detector components, we predict the nuclear recoil backgrounds for the WIMP search results published by the XENON100 experiment in 2011 and 2012, 0.11 events and 0.17 events, respectively, and conclude that they do not limit the sensitivity of the experiment.
We describe the purification of xenon from traces of the radioactive noble gas radon using a cryogenic distillation column. The distillation column was integrated into the gas purification loop of ...the XENON100 detector for online radon removal. This enabled us to significantly reduce the constant 222Rn background originating from radon emanation. After inserting an auxiliary 222Rn emanation source in the gas loop, we determined a radon reduction factor of R>27 (95% C.L.) for the distillation column by monitoring the 222Rn activity concentration inside the XENON100 detector.
Full text
Available for:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We describe the purification of xenon from traces of the radioactive noble gas radon using a cryogenic distillation column. The distillation column was integrated into the gas purification loop of ...the XENON100 detector for online radon removal. This enabled us to significantly reduce the constant
222
Rn background originating from radon emanation. After inserting an auxiliary
222
Rn emanation source in the gas loop, we determined a radon reduction factor of
R
>
27
(95% C.L.) for the distillation column by monitoring the
222
Rn activity concentration inside the XENON100 detector.
Full text
Available for:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The XENON100 experiment has completed a dark matter search with 100.9 live days of data, taken from January to June 2010. Events with energies between 8.4 and 44.6 keVnr in a fiducial volume ...containing 48 kg of liquid xenon have been analyzed. A total of three events have been found in the predefined signal region, compatible with the background prediction of (1.8±0.6) events. Based on this analysis we present limits on the WIMP-nucleon cross section for inelastic dark matter. With the present data we are able to rule out the explanation for the observed DAMA/LIBRA modulation as being due to inelastic dark matter scattering off iodine, at a 90% confidence level.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UM
PDF
