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.
To satisfy the requirements of the next generation of dark matter detectors based on the dual phase TPC, Hamamatsu, in close collaboration with UCLA, has developed the R11410-10 photomultiplier tube. ...In this work, we present the detailed tests performed on this device. High QE (∼30%) accompanied by a low dark count rate (50Hz at 0.3 PE) and high gain (1×107) with good single PE resolution have been observed. A comprehensive screening measurement campaign is ongoing while the manufacturer quotes a radioactivity of 20mBq/PMT. These characteristics show the R11410-10 to be particularly suitable for the forthcoming zero background liquid xenon detectors.
► Requirements needed of PMTs for dark matter searches. ► Systematic tests of 3-in. Hamamatsu R11410-PMT for dark matter detectors. ► Results show high quantum efficiency, low radioactivity, and low noise properties. ► PMT demonstrates suitable qualities necessary for rare event searches.
► Material selection based on their intrinsic radioactive contaminations is crucial for low background experiments. ► We present detailed results from the material screening and selection campaign ...for the XENON100 dark matter experiment. ► The measurements were performed using low background gamma-ray spectrometry and mass spectrometry.
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.
Dark matter and double beta decay experiments require extremely low radioactivity within the detector materials. For this purpose, the University of California, Los Angeles and Hamamatsu Photonics ...have developed the QUartz Photon Intensifying Detector (Q
upid), an ultra-low background photodetector based on the Hybrid Avalanche Photo Diode (HAPD) and entirely made of ultraclean synthetic fused silica. In this work we present the basic concept of the Q
upid and the testing measurements on Q
upids from the first production line.
Screening of radioactivity at the Gator facility in the Laboratori Nazionali del Gran Sasso has shown that the Q
upids safely fulfill the low radioactive contamination requirements for the next generation zero background experiments set by Monte Carlo simulations.
The quantum efficiency of the Q
upid at room temperature is
>
30
% at the xenon scintillation wavelength. At −100
°C, the Q
upid shows a leakage current smaller than 1
nA and a global gain of 10
5. In these conditions, the photocathode and the anode show
>
95
%
linearity up to
1
μ
A
for the cathode and 3
mA for the anode. The photocathode and collection efficiency are uniform to 80% over the entire surface. In parallel with single photon counting capabilities, the Q
upids have a good timing response: 1.8 ±0.1
ns rise time, 2.5 ±0.2
ns fall time, 4.20 ±0.05
ns (FWHM) pulse width, and 160 ±30
ps (FWHM) transit time spread.
The Q
upids have also been tested in a liquid xenon environment, and scintillation light from
57Co and
210Po radioactive sources was observed.
► We propose a 3-stage DM and Iˆ1/2 observatory based on multi-ton LXe and LAr detectors. ► This work is a quantitative study of the topics in Astropart. Phys. 31 (2009) 63–74. ► WIMP cross-sections ...and masses could be measured with sensitivity of 10-47cm2. ► 0ν2β decay could be observed for 136Xe with sensitivity to half-lives 10E27–10E28y. ► The pp solar ν spectrum, and ν flux from a Galactic SN, could also be measured.
We study a three stage dark matter and neutrino observatory based on multi-ton two-phase liquid Xe and Ar detectors with sufficiently low backgrounds to be sensitive to WIMP dark matter interaction cross sections down to 10-47cm2, and to provide both identification and two independent measurements of the WIMP mass through the use of the two target elements in a 5:1 mass ratio, giving an expected similarity of event numbers. The same detection systems will also allow measurement of the pp solar neutrino spectrum, the neutrino flux and temperature from a Galactic supernova, and neutrinoless double beta decay of 136Xe to the lifetime level of 1027–1028y corresponding to the Majorana mass predicted from current neutrino oscillation data. The proposed scheme would be operated in three Generic stages G2, G3, G4, beginning with fiducial masses 1-ton Xe+5-ton Ar (G2), progressing to 10-ton Xe+50-ton Ar (G3) then, dependent on results and performance of the latter, expandable to 100-ton Xe+500-ton Ar (G4). This method of scale-up offers the advantage of utilizing the Ar vessel and ancillary systems of one stage for the Xe detector of the succeeding stage, requiring only one new detector vessel at each stage. Simulations show the feasibility of reducing or rejecting all external and internal background levels to a level <1 events per year for each succeeding mass level, by utilizing an increasing outer thickness of target material as self-shielding. The system would, with increasing mass scale, become increasingly sensitive to annual signal modulation, the agreement of Xe and Ar results confirming the Galactic origin of the signal. Dark matter sensitivities for spin-dependent and inelastic interactions are also included, and we conclude with a discussion of possible further gains from the use of Xe/Ar mixtures.
A multi-target detection system XAX, comprising concentric 10
ton targets of
136Xe and
129/131Xe, together with a geometrically similar or larger target of liquid Ar, is described. Each is configured ...as a two-phase scintillation/ionization TPC detector, enhanced by a full 4π array of ultra-low radioactivity quartz photon intensifying detectors (QUPIDs) replacing the conventional photomultipliers for detection of scintillation light. It is shown that background levels in XAX can be reduced to the level required for dark matter particle (WIMP) mass measurement at a 10
−10
pb WIMP-nucleon cross-section, with single-event sensitivity below 10
−11
pb. The use of multiple target elements allows for confirmation of the
A
2 dependence of a coherent cross-section, and the different Xe isotopes provide information on the spin-dependence of the dark matter interaction. The event rates observed by Xe and Ar would modulate annually with opposite phases from each other for WIMP mass >∼100
GeV/c
2. The large target mass of
136Xe and high degree of background reduction allow neutrinoless double beta decay to be observed with lifetimes of 10
27–10
28 years, corresponding to the Majorana neutrino mass range 0.01–0.1
eV, the most likely range from observed neutrino mass differences. The use of a
136Xe-depleted
129/131Xe target will also allow measurement of the pp solar neutrino spectrum to a precision of 1–2%.
We report on a search for particle dark matter with the XENON100 experiment, operated at the Laboratori Nazionali del Gran Sasso for 13 months during 2011 and 2012. XENON100 features an ultralow ...electromagnetic background of (5.3 ± 0.6) × 10(-3) events/(keV(ee) × kg × day) in the energy region of interest. A blind analysis of 224.6 live days × 34 kg exposure has yielded no evidence for dark matter interactions. The two candidate events observed in the predefined nuclear recoil energy range of 6.6-30.5 keV(nr) are consistent with the background expectation of (1.0 ± 0.2) events. A profile likelihood analysis using a 6.6-43.3 keV(nr) energy range sets the most stringent limit on the spin-independent elastic weakly interacting massive particle-nucleon scattering cross section for weakly interacting massive particle masses above 8 GeV/c(2), with a minimum of 2 × 10(-45) cm(2) at 55 GeV/c(2) and 90% confidence level.
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.
We present new experimental constraints on the elastic, spin-dependent WIMP-nucleon cross section using recent data from the XENON100 experiment, operated in the Laboratori Nazionali del Gran Sasso ...in Italy. An analysis of 224.6 live days×34 kg of exposure acquired during 2011 and 2012 revealed no excess signal due to axial-vector WIMP interactions with 129Xe and 131Xe nuclei. This leads to the most stringent upper limits on WIMP-neutron cross sections for WIMP masses above 6 GeV/c², with a minimum cross section of 3.5×10(-40) cm² at a WIMP mass of 45 GeV/c², at 90% confidence level.
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