Showing papers by "Graciela B. Gelmini published in 2009"
TL;DR: In this paper, the authors examined the effect of channeling on the DAMA/NaI/DAMA/LIBRA energy spectrum of the combined DAMA modulation data, which may be interpreted as a signal for the existence of weakly interacting dark matter (WIMPs) in our galactic halo.
Abstract: The DAMA/NaI and DAMA/LIBRA annual modulation data, which may be interpreted as a signal for the existence of weakly interacting dark matter (WIMPs) in our galactic halo, are examined in light of null results from other experiments: CDMS, XENON10, CRESST I, CoGeNT, TEXONO, and Super-Kamiokande (SuperK). We use the energy spectrum of the combined DAMA modulation data given in 36 bins, and include the effect of channeling. Several statistical tools are implemented in our study: likelihood ratio with a global fit and with raster scans in the WIMP mass and goodness-of-fit (g.o.f.). These approaches allow us to differentiate between the preferred (global best fit) and allowed (g.o.f.) parameter regions. It is hard to find WIMP masses and couplings consistent with all existing data sets; the surviving regions of parameter space are found here. For spin-independent (SI) interactions, the best fit DAMA regions are ruled out to the 3σ C.L., even with channeling taken into account. However, for WIMP masses of ~ 8 GeV some parameters outside these regions still yield a moderately reasonable fit to the DAMA data and are compatible with all 90% C.L. upper limits from negative searches, when channeling is included. For spin-dependent (SD) interactions with proton-only couplings, a range of masses below 10 GeV is compatible with DAMA and other experiments, with and without channeling, when SuperK indirect detection constraints are included; without the SuperK constraints, masses as high as ~ 20 GeV are compatible. For SD neutron-only couplings we find no parameters compatible with all the experiments. Mixed SD couplings are examined: e.g. ~ 8 GeV mass WIMPs with an = ±ap are found to be consistent with all experiments. In short, there are surviving regions at low mass for both SI and SD interactions; if indirect detection limits are relaxed, some SD proton-only couplings at high masses also survive.
487 citations
TL;DR: In this article, the authors obtained upper limits of 3.8, 2.4, 3.5, and 11.7% on the fraction of cosmic-ray photons above 2, 3, 5 and 10 EeV.
162 citations
TL;DR: In this paper, the Pierre Auger Observatory data were used to establish an upper limit on the diffuse flux of tau neutrinos in the cosmic radiation, and the search procedure to select events induced by tau decays against the background of normal showers induced by cosmic rays was described.
Abstract: Data collected at the Pierre Auger Observatory are used to establish an upper limit on the diffuse flux of tau neutrinos in the cosmic radiation. Earth-skimming nu(tau) may interact in the Earth's crust and produce a tau lepton by means of charged-current interactions. The tau lepton may emerge from the Earth and decay in the atmosphere to produce a nearly horizontal shower with a typical signature, a persistent electromagnetic component even at very large atmospheric depths. The search procedure to select events induced by tau decays against the background of normal showers induced by cosmic rays is described. The method used to compute the exposure for a detector continuously growing with time is detailed. Systematic uncertainties in the exposure from the detector, the analysis, and the involved physics are discussed. No tau neutrino candidates have been found. For neutrinos in the energy range 2x10(17) eV
133 citations
TL;DR: In this article, the authors studied the impact of atmospheric variations on extensive air showers by means of the surface detector of the Pierre Auger Observatory and found that the observed behaviour is explained by a model including the effects associated with the variations of P and ρ.
54 citations
01 Jan 2009
TL;DR: The 31st International Cosmic Ray Conference (ICRC) as discussed by the authors was held at the Pierre Auger Observatory in the Polish city of Lodz during July 2009, where the authors presented a Monte Carlo exploration of methods to determine the nuclear mass composition of UHECR with the surface detectors.
Abstract: These are presentations to be presented at the 31st International Cosmic Ray Conference, in Lodz, Poland during July 2009. It consists of the following presentations: (1) Measurement of the average depth of shower maximum and its fluctuations with the Pierre Auger Observatory; (2) Study of the nuclear mass composition of UHECR with the surface detectors of the Pierre Auger Observatory; (3) Comparison of data from the Pierre Auger Observatory with predictions from air shower simulations: testing models of hadronic interactions; (4) A Monte Carlo exploration of methods to determine the UHECR composition with the Pierre Auger Observatory; (5) The delay of the start-time measured with the Pierre Auger Observatory for inclined showers and a comparison of its variance with models; (6) UHE neutrino signatures in the surface detector of the Pierre Auger Observatory; and (7) The electromagnetic component of inclined air showers at the Pierre Auger Observatory.
44 citations
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TL;DR: In this paper, the correlations of ultra-high energy cosmic ray directions with extra-Galactic objects, of general anisotropy, of photons and neutrinos, and of other astrophysical effects, with the Pierre Auger Observatory were studied.
Abstract: Studies of the correlations of ultra-high energy cosmic ray directions with extra-Galactic objects, of general anisotropy, of photons and neutrinos, and of other astrophysical effects, with the Pierre Auger Observatory. Contributions to the 31st ICRC, Lodz, Poland, July 2009.
43 citations
Posted Content•
TL;DR: In this paper, the authors studied the composition of the highest energy cosmic rays with the Pierre Auger Observatory, including examination of hadronic physics effects on the structure of extensive air showers.
Abstract: Studies of the composition of the highest energy cosmic rays with the Pierre Auger Observatory, including examination of hadronic physics effects on the structure of extensive air showers. Submissions to the 31st ICRC, Lodz, Poland (July 2009).
37 citations
Posted Content•
TL;DR: Technical reports on operations and features of the Pierre Auger Observatory, including ongoing and planned enhancements and the status of the future northern hemisphere portion of the Observatory, were presented at the 31st International Cosmic Ray Conference, Lodz, Poland, as discussed by the authors.
Abstract: Technical reports on operations and features of the Pierre Auger Observatory, including ongoing and planned enhancements and the status of the future northern hemisphere portion of the Observatory. Contributions to the 31st International Cosmic Ray Conference, Lodz, Poland, July 2009.
19 citations
01 Jan 2009
TL;DR: In this paper, atmospheric monitoring, calibration, and other operating systems of the Pierre Auger Observatory are described. Contributions to the 31st International Cosmic Ray Conference, Lodz, Poland, July 2009.
Abstract: Reports on the atmospheric monitoring, calibration, and other operating systems of the Pierre Auger Observatory. Contributions to the 31st International Cosmic Ray Conference, Lodz, Poland, July 2009.
9 citations
01 Oct 2009
TL;DR: In this paper, different pre-BBN cosmological models affect the properties of WIMPs and neutrinos, and these properties could thus allow to determine the evolution of the universe before Big Bang Nucleosynthesis.
Abstract: If detected, dark matter particles such as WIMPs and sterile neutrinos will be the earliest relics we can study, the first coming from before Big Bang Nucleosynthesis, an epoch from which we have no data so far. Here we discuss how different pre-BBN cosmological models affect the properties of these particles, and how these properties could thus allow to determine the evolution of the Universe before BBN.
6 citations
TL;DR: In this paper, different pre-BBN cosmological models affect the properties of WIMPs and neutrinos, and these properties could thus allow to determine the evolution of the universe before Big Bang Nucleosynthesis.
Abstract: If detected, dark matter particles such as WIMPs and sterile neutrinos will be the earliest relics we can study, the first coming from before Big Bang Nucleosynthesis, an epoch from which we have no data so far. Here we discuss how different pre-BBN cosmological models affect the properties of these particles, and how these properties could thus allow to determine the evolution of the Universe before BBN.
01 Jun 2009
TL;DR: Technical reports on operations and features of the Pierre Auger Observatory, including ongoing and planned enhancements and the status of the future northern hemisphere portion of the Observatory, were presented at the 31st International Cosmic Ray Conference, Lodz, Poland, as discussed by the authors.
Abstract: Technical reports on operations and features of the Pierre Auger Observatory, including ongoing and planned enhancements and the status of the future northern hemisphere portion of the Observatory. Contributions to the 31st International Cosmic Ray Conference, Lodz, Poland, July 2009.
TL;DR: In this paper, the authors review some of the physics we are learning and expect to learn in the near future through the observation of cosmic rays and discuss the data of the Pierre Auger Observatory, PAMELA, ATIC and FST among other experiments.
Abstract: I review here some of the physics we are learning and expect to learn in the near future through the observation of cosmic rays. The study of cosmic rays involves a combination of data from accelerators, ground arrays, atmospheric fluorescence detectors and balloon and satellite experiments. I will discuss the data of the Pierre Auger Observatory, PAMELA, ATIC and FST among other experiments.
01 Jun 2009
TL;DR: In this paper, the authors review some of the physics we are learning and expect to learn in the near future through the observation of cosmic rays and discuss the data of the Pierre Auger Observatory, PAMELA, ATIC and FST among other experiments.
Abstract: I review here some of the physics we are learning and expect to learn in the near future through the observation of cosmic rays. The study of cosmic rays involves a combination of data from accelerators, ground arrays, atmospheric fluorescence detectors and balloon and satellite experiments. I will discuss the data of the Pierre Auger Observatory, PAMELA, ATIC and FST among other experiments.
01 Jun 2009
TL;DR: In this article, the authors studied the cosmic ray energy spectrum at the highest energies with the Pierre Auger Observatory (PAO) and found that the spectrum at highest energies at the PAO is very similar to ours.
Abstract: Studies of the cosmic ray energy spectrum at the highest energies with the Pierre Auger Observatory.
TL;DR: The channeling of the recoiling nucleus in crystalline detectors after a WIMP collision would produce a larger scintillation or ionization signal in direct detection experiments than otherwise expected as discussed by the authors.
Abstract: The channeling of the recoiling nucleus in crystalline detectors after a WIMP collision would produce a larger scintillation or ionization signal in direct detection experiments than otherwise expected. I present estimates of the importance of this effect for the total direct detection rate and the daily modulation of the signal using analytic models produced in the 1960's and 70's to describe the effects of channeling and blocking in crystals.