Classicalpaper3

Observation of an anomalous positron abundance in the cosmic radiation

O. Adriani, G. C. Barbarino, G. A. Bazilevskaya, R. Bellotti, M. Boezio, E. A. Bogomolov, L. Bonechi, M. Bongi, V. Bonvicini, S. Bottai, A. Bruno, F. Cafagna, D. Campana, P. Carlson, M. Casolino, G. Castellini, M. P. De Pascale, G. De Rosa, N. De Simone, V. Di Felice, A. M. Galper, L. Grishantseva, P. Hofverberg, S. V. Koldashov, S. Y. Krutkov, A. N. Kvashnin, A. Leonov, V. Malvezzi, L. Marcelli, W. Menn, V. V. Mikhailov, E. Mocchiutti, S. Orsi, G. Osteria, P. Papini, M. Pearce, P. Picozza, M. Ricci, S. B. Ricciarini, M. Simon, R. Sparvoli, P. Spillantini, Y. I. Stozhkov, A. Vacchi, E. Vannuccini, G. Vasilyev, S. A. Voronov, Y. T. Yurkin, G. Zampa, N. Zampa, V. G. Zverev

Positrons are known to be produced in interactions between cosmic-ray nuclei and interstellar matter ("secondary production"). Positrons may, however, also be created by dark matter particle annihilations in the galactic halo or in the magnetospheres of near-by pulsars. The nature of dark matter is one of the most prominent open questions in science today. An observation of positrons from pulsars would open a new observation window on these sources. Here we present results from the PAMELA satellite experiment on the positron abundance in the cosmic radiation for the energy range 1.5 - 100 GeV. Our high energy data deviate significantly from predictions of secondary production models, and may constitute the first indirect evidence of dark matter particle annihilations, or the first observation of positron production from near-by pulsars. We also present evidence that solar activity significantly affects the abundance of positrons at low energies.

Links : https://arxiv.org/abs/0810.4995

Dark Matter Results from 2Dark Matter Results from 225 Live Days of XENON100 Data25 Live Days of XENON100 Data

XENON100 Collaboration: E. Aprile, M. Alfonsi, K. Arisaka, F. Arneodo, C. Balan, L. Baudis, B. Bauermeister, A. Behrens, P. Beltrame, K. Bokeloh, E. Brown, G. Bruno, R. Budnik, J. M. R. Cardoso, W.-T. Chen, B. Choi, D. Cline, A. P. Colijn, H. Contreras, J. P. Cussonneau, M. P. Decowski, E. Duchovni, S. Fattori, A. D. Ferella, W. Fulgione, F. Gao, M. Garbini, C. Ghag, K.-L. Giboni, L. W. Goetzke, C. Grignon, E. Gross, W. Hampel, F. Kaether, 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, A. J. Melgarejo Fernandez, Y. Meng, A. Molinario, E. Nativ, K. Ni, U. Oberlack, S. E. A. Orrigo, E. Pantic, R. Persiani, G. Plante, N. Priel, A. Rizzo, S. Rosendahl, et al. (15 additional authors not shown)

We report on a search for particle dark matter with the XENON100 experiment, operated at the Laboratori Nazionali del Gran Sasso (LNGS) for 13 months during 2011 and 2012. XENON100 features an ultra-low electromagnetic background of (5.3 \pm 0.6) \times 10^-3 events (kg day keVee)^-1 in the energy region of interest. A blind analysis of 224.6 live days \times 34 kg exposure has yielded no evidence for dark matter interactions. The two candidate events observed in the pre-defined nuclear recoil energy range of 6.6-30.5 keVnr are consistent with the background expectation of (1.0 \pm 0.2) events. A Profile Likelihood analysis using a 6.6-43.3 keVnr energy range sets the most stringent limit on the spin-independent elastic WIMP-nucleon scattering cross section for WIMP masses above 8 GeV/c^2, with a minimum of 2 \times 10^-45 cm^2 at 55 GeV/c^2 and 90% confidence level.

Links : https://arxiv.org/abs/1207.5988

The XENON100 Dark Matter Experiment

XENON100 Collaboration: E. Aprile, K. Arisaka, F. Arneodo, A. Askin, L. Baudis, A. Behrens, E. Brown, J. M. R. Cardoso, B. Choi, D. Cline, S. Fattori, A. D. Ferella, K. L. Giboni, A. Kish, C. W. Lam, R. F. Lang, K. E. Lim, J. A. M. Lopes, T. Marrodan 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, E. Tziaferi, H. Wang, M. Yamashita

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-nucleo scattering cross section sensitivity of \sigma = 2x10^-45 cm^2 for a 100 GeV/c^2 WIMP.

Links : https://arxiv.org/abs/1107.2155