* Astronomy

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RE: XENON100 Experiment

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Title: Analysis of the XENON100 Dark Matter Search Data
Authors: E. Aprile, M. Alfonsi, K. Arisaka, F. Arneodo, C. Balan, L. Baudis, A. Behrens, P. Beltrame, K. Bokeloh, E. Brown, G. Bruno, R. Budnik, J.M.R. Cardoso, W.-T. Chen, B. Choi, D. B. Cline, H. Contreras, J.P. Cussonneau, M.P. Decowski, E. Duchovni, S. Fattori, A.D. Ferella, W. Fulgione, F. Gao, M. Garbini, K.-L. Giboni, L.W. Goetzke, C. Grignon, E. Gross, W. Hampel, H. Kettling, A. Kish, J. Lamblin, H. Landsman, R. F. Lang, M. Le Calloch, C. Levy, K. E. Lim, Q. Lin, S. Lindemann, M. Lindner, J. A. M. Lopes, K. Lung, T. Marrodan Undagoitia, F. V. Massoli, Y. Mei, A. J. Melgarejo Fernandez, Y. Meng, A. Molinario, E. Nativ, K. Ni, U. Oberlack, S. E. A. Orrigo, E. Pantic, D. Pätzold, R. Persiani, G. Plante, N. Priel, A. Rizzo, S. Rosendahl, J. M. F. dos Santos, G. Sartorelli, J. Schreiner, M. Schumann, et al. (11 additional authors not shown)

The XENON100 experiment, situated in the Laboratori Nazionali del Gran Sasso, aims at the direct detection of dark matter in the form of weakly interacting massive particles (WIMPs), based on their interactions with xenon nuclei in an ultra low background dual-phase time projection chamber. This paper describes the general methods developed for the analysis of the XENON100 data, focusing on the 100.9 live days science run from which results on spin-independent elastic and inelastic WIMP-nucleon cross-sections have already been reported.

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Title: Results from the XENON100 Dark Matter Search Experiment
Authors: Laura Baudis, for the XENON Collaboration

XENON100 is a liquid xenon time projection chamber built to search for rare collisions of hypothetical, weakly interacting massive particles (WIMPs), which are candidates for the dark matter in our universe, with xenon atoms. Operated in a low-background shield at the Gran Sasso Underground Laboratory in Italy, XENON100 has reached the unprecedented background level of <0.15 events/(day keV) in the energy range below 100 keV in 30 kg of target mass, before electronic/nuclear recoil discrimination. It found no evidence for WIMPs during a dark matter run lasting for 100.9 live days in 2010, excluding with 90% confidence scalar WIMP-nucleon cross sections above 7e-45 cm² at a WIMP mass of 50 GeV/c². A new run started in March 2011, and more than 210 live days of WIMP-search data were acquired. Results are expected to be released in spring 2012. The construction of the ton-scale XENON1T detector in Hall B of the Gran Sasso Laboratory will start in late 2012.

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Search for dark matter moves one step closer to detecting elusive particle

And while the XENON100 experiment found no dark matter signal in 100 days of testing, the researcher's newly calculated upper limits on the mass of WIMPs and the probability of their interacting with other particles are the best in the world, said UCLA physics professor Katsushi Arisaka, a member of the international collaboration.
Even though the experiment did not detect a WIMP, the progress sets the stage for an ambitious next-generation project called XENON1T, which will use a much larger, one-ton liquid xenon instrument with highly specialised light-detectors developed at UCLA that make it 100 times more sensitive than XENON100, said David Cline, a UCLA professor of physics and founder of UCLA's dark matter group.
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Title: Dark Matter Results from 100 Live Days of XENON100 Data
Authors: XENON100 Collaboration: E. Aprile, K. Arisaka, F. Arneodo, A. Askin, L. Baudis, A. Behrens, K. Bokeloh, E. Brown, T. Bruch, G. Bruno, J. M. R. Cardoso, W.-T. Chen, B. Choi, D. Cline, E. Duchovni, S. Fattori, A. D. Ferella, F. Gao, K.-L. Giboni, E. Gross, A. Kish, C. W. Lam, J. Lamblin, R. F. Lang, C. Levy, K. E. Lim, Q. Lin, S. Lindemann, M. Lindner, J. A. M. Lopes, K. Lung, T. Marrodan Undagoitia, Y. Mei, A. J. Melgarejo Fernandez, K. Ni, U. Oberlack, S. E. A. Orrigo, E. Pantic, R. Persiani, G. Plante, A. C. C. Ribeiro, R. Santorelli, J. M. F. dos Santos, G. Sartorelli, M. Schumann, M. Selvi, P. Shagin, H. Simgen, A. Teymourian, D. Thers, O. Vitells, H. Wang, M. Weber, C. Weinheimer

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 millimetre precision allows to select only the innermost 48 kg as ultra-low 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 a pre-defined 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 WIMP-nucleon scattering cross-sections above 7.0x10^-45 cm^2 for a WIMP mass of 50 GeV/c^2 at 90% confidence level.

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A new widely anticipated experiment underneath a mountain in Italy designed to detect a sea of dark particles that allegedly constitute a quarter of creation did not see anything during a test run last fall, scientists reported Saturday.
But, they said, the clarity with which they saw nothing spurred hopes that such experiments are approaching the rigor and sensitivity necessary to detect the elusive gravitational glue of the cosmos. The results also cast further doubt on some controversial claims that dark matter has already been seen.
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SUSY Dark Matter/Interactive Direct Detection Limit Plotter

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Radioactivity challenges dark-matter detector

Time is running out for Elena Aprile, a physicist at Columbia University in New York. In mid-March, she is scheduled to present the results of a dark-matter experiment at a workshop in Venice, Italy, but she doesn't have the results yet.
She and the rest of her team have blinded themselves to the data to avoid bias, while they wrestle with an analysis that needs to take account of radioactive contamination in their detector.
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Early Results from Large Dark Matter Detector Cast Doubt on Earlier Claims

An experiment looking for the signal of dark matter deep in an underground lab in Italy turned up no candidate signals in 11 days of early operation, the experimental collaboration reported in a paper posted online Monday. The underground detector, called XENON100, only recently began taking data but is already challenging prior claims and hints of dark matter signals.
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Title: First Dark Matter Results from the XENON100 Experiment
Authors: E. Aprile, K. Arisaka, F. Arneodo, A. Askin, L. Baudis, A. Behrens, E. Brown, J. M. R. Cardoso, B. Choi, D. B. Cline, S. Fattori, A. D. Ferella, K.-L. Giboni, K. Hugenberg, A. Kish, C. W. Lam, J. Lamblin, R. F. Lang, K. E. Lim, J. A. M. Lopes, T. Marrodán Undagoitia, Y. Mei, A. J. Melgarejo Fernandez, K. Ni, U. Oberlack, S. E. A. Orrigo, E. Pantic, G. Plante, A. C. C. Ribeiro, R. Santorelli, J. M. F. dos Santos, M. Schumann, P. Shagin, A. Teymourian, D. Thers, E. Tziaferi, H. Wang, C. Weinheimer (XENON100 Collaboration)

The XENON100 experiment, in operation at the Laboratori Nazionali del Gran Sasso in Italy, is designed to search for dark matter WIMPs scattering off 62 kg of liquid xenon in an ultra-low background dual-phase time projection chamber. In this letter, we present first dark matter results from the analysis of 11.17 live days of non-blind data, acquired in October and November 2009. In the selected fiducial target of 40 kg, and within the pre-defined signal region, we observe no events and hence exclude spin-independent WIMP-nucleon elastic scattering cross-sections above 3 x 10^-44 cm² for 50 GeV/c² WIMPs at 90% confidence level. Below 20 GeV/c^2, this result challenges the interpretation of the CoGeNT or DAMA signals as being due to spin-independent, elastic, light mass WIMP interactions.

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