[Show abstract][Hide abstract]ABSTRACT: The XENON100 experiment, in operation at the Laboratori Nazionali del Gran
Sasso (LNGS) in Italy, was designed to search for evidence of dark matter
interactions inside a volume of liquid xenon using a dual-phase time projection
chamber. This paper describes the Slow Control System (SCS) of the experiment
with emphasis on the distributed architecture as well as on its modular and
expandable nature. The system software was designed according to the rules of
Object-Oriented Programming and coded in Java, thus promoting code reusability
and maximum flexibility during commissioning of the experiment. The SCS has
been continuously monitoring the XENON100 detector since mid 2008, remotely
recording hundreds of parameters on a few dozen instruments in real time, and
setting emergency alarms for the most important variables.
Full-text · Article · Nov 2012 · Journal of Instrumentation
[Show abstract][Hide abstract]ABSTRACT: We present results from the direct search for dark matter with the XENON100 detector, installed underground at the Laboratori Nazionali del Gran Sasso of INFN, Italy. XENON100 is a two-phase time-projection chamber with a 62 kg liquid xenon target. Interaction vertex reconstruction in three dimensions with millimeter precision allows the selection of only the innermost 48 kg as the ultralow background fiducial target. In 100.9 live days of data, acquired between January and June 2010, no evidence for dark matter is found. Three candidate events were observed in the signal region with an expected background of (1.8 ± 0.6) events. This leads to the most stringent limit on dark matter interactions today, excluding spin-independent elastic weakly interacting massive particle (WIMP) nucleon scattering cross sections above 7.0 × 10(-45) cm(2) for a WIMP mass of 50 GeV/c(2) at 90% confidence level.
[Show abstract][Hide abstract]ABSTRACT: Results of the extensive radioactivity screening campaign to identify materials for the construction of XENON100 are reported. This Dark Matter search experiment is operated underground at Laboratori Nazionali del Gran Sasso (LNGS), Italy. Several ultra sensitive High Purity Germanium detectors (HPGe) have been used for gamma ray spectrometry. Mass spectrometry has been applied for a few low mass plastic samples. Detailed tables with the radioactive contaminations of all screened samples are presented, together with the implications for XENON100.
[Show abstract][Hide abstract]ABSTRACT: The XENON100 dark matter experiment uses liquid xenon (LXe) in a time
projection chamber (TPC) to search for Xe nuclear recoils resulting from the
scattering of dark matter Weakly Interacting Massive Particles (WIMPs). In this
paper we present a detailed description of the detector design and present
performance results, as established during the commissioning phase and during
the first science runs.
The active target of XENON100 contains 62 kg of LXe, surrounded by an LXe
veto of 99 kg, both instrumented with photomultiplier tubes (PMTs) operating
inside the liquid or in Xe gas. The LXe target and veto are contained in a
low-radioactivity stainless steel vessel, embedded in a passive radiation
shield. The experiment is installed underground at the Laboratori Nazionali del
Gran Sasso (LNGS), Italy and has recently published results from a 100
live-days dark matter search. The ultimate design goal of XENON100 is to
achieve a spin-independent WIMP-nucleon scattering cross section sensitivity of
\sigma = 2x10^-45 cm^2 for a 100 GeV/c^2 WIMP.
[Show abstract][Hide abstract]ABSTRACT: The XENON100 experiment has recently completed a dark matter run with 100.9
live-days of data, taken from January to June 2010. Events in a 48kg fiducial
volume in the energy range between 8.4 and 44.6 keVnr have been analyzed. A
total of three events have been found in the predefined signal region,
compatible with the background prediction of (1.8 \pm 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 · Article · Apr 2011 · Physical Review D
[Show abstract][Hide abstract]ABSTRACT: 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 · Article · Mar 2011 · Physical Review D
[Show abstract][Hide abstract]ABSTRACT: The XENON100 experiment, in operation at the Laboratori Nazionali del Gran Sasso in Italy, is designed to search for dark matter weakly interacting massive particles (WIMPs) scattering off 62 kg of liquid xenon in an ultralow background dual-phase time projection chamber. In this Letter, we present first dark matter results from the analysis of 11.17 live days of nonblind data, acquired in October and November 2009. In the selected fiducial target of 40 kg, and within the predefined signal region, we observe no events and hence exclude spin-independent WIMP-nucleon elastic scattering cross sections above 3.4 × 10⁻⁴⁴ cm² for 55 GeV/c² WIMPs at 90% confidence level. Below 20 GeV/c², this result constrains the interpretation of the CoGeNT and DAMA signals as being due to spin-independent, elastic, light mass WIMP interactions.
[Show abstract][Hide abstract]ABSTRACT: The recently submitted preprint on the first results from the XENON100 dark
matter experiment (arxiv:1005.0380) was followed by a criticism by J.I. Collar
and D.N. McKinsey (arxiv:1005.0838), focused on our extrapolation of the
scintillation efficiency L_eff to the lowest nuclear recoil energies, where no
data and no theoretical model exist. Here we add clarifications on our analysis
and comment on their criticism.