Showing papers by "Graciela B. Gelmini published in 2004"
TL;DR: A scenario, based on a low reheating temperature T(R)<<100 MeV at the end of (the last episode of) inflation, in which the coupling of sterile neutrinos to active neut rinos can be as large as experimental bounds permit (thus making this neutrino "visible" in future experiments).
Abstract: We present here a scenario, based on a low reheating temperature ${T}_{R}\ensuremath{\ll}100\text{ }\text{ }\mathrm{M}\mathrm{e}\mathrm{V}$ at the end of (the last episode of) inflation, in which the coupling of sterile neutrinos to active neutrinos can be as large as experimental bounds permit (thus making this neutrino ``visible'' in future experiments). In previous models this coupling was forced to be very small to prevent a cosmological overabundance of sterile neutrinos. Here the abundance depends on how low the reheating temperature is. For example, the sterile neutrino required by the Liquid Scintillator Neutrino Detector result may not have any cosmological problem within our scenario.
191 citations
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TL;DR: In this paper, the authors present two examples of velocity distributions for light dark matter particles that reconcile the annual modulation signal observed by DAMA with all other negative results from dark matter searches.
Abstract: We present two examples of velocity distributions for light dark matter particles that reconcile the annual modulation signal observed by DAMA with all other negative results from dark matter searches. They are: (1) a conventional Maxwellian distribution for particle masses of 6 to 9 GeV; (2) a dark matter stream coming from the general direction of Galactic rotation (not the Sagittarius stream). Our idea is based on having a signal in Na, instead of I, in DAMA, and can be tested in the immediate future by CDMS-II (using Si) and CRESST-II (using O).
38 citations
TL;DR: In this paper, it was shown that the non-observation of cosmic ray events at energies above 2 ×10 20 eV by the AGASA Collaboration implies a lower bound ∼ 0.3 eV on the relic neutrino mass.
Abstract: Neutrinos from far-away sources annihilating at the Z resonance on relic neutrinos may give origin to the extreme-energy cosmic rays (EECR). If “Z-bursts” are responsible for the EECR events, then we show that the non-observation of cosmic ray events at energies above 2 ×10 20 eV by the AGASA Collaboration implies a lower bound ∼ 0.3 eV on the relic neutrino mass. Since this mass exceeds the mass-squared differences inferred from oscillation physics, the bound in fact applies to all three neutrino masses. Together with the upper bound provided by comparisons of the CMB anisotropy with largescale structure, this bound leaves only a small interval for neutrino masses around 0.3 eV, if Z-bursts are to explain the existing EECR events.
14 citations
TL;DR: The Cosmic Neutrino Background (C$
u$B) is the oldest relic from the Big Bang, produced a few seconds after the Bang itself, and it has not so far been observed as discussed by the authors.
Abstract: Unlike the relic photons, relic neutrinos have not so far been observed. The Cosmic Neutrino Background (C$
u$B) is the oldest relic from the Big Bang, produced a few seconds after the Bang itself. Due to their impact in cosmology, relic neutrinos may be revealed indireclty in the near future through cosmological observations. In this talk we concentrate on other proposals, made in the last 30 years, to try to detect the C$
u$B directly, either in laboratory searches (through tiny accelerations they produce on macroscopic targets) or through astrophysical observations (looking for absorption dips in the flux of Ultra-High Energy neutrinos, due to the annihilation of these neutrinos with relic neutrinos at the Z-resonance). We concentrate mainly on the first of these two possibilities.
7 citations
TL;DR: In this paper, it was shown that the abundance of sterile neutrinos becomes largely independent of their coupling to active neutrino, and thus, cosmological bounds become less stringent than usually assumed.
Abstract: We point out that in scenarios with a low reheating temperature $T_R << 100$ MeV at the end of (the last episode of) inflation or entropy production, the abundance of sterile neutrinos becomes largely independent of their coupling to active neutrinos. Thus, cosmological bounds become less stringent than usually assumed, allowing sterile neutrinos to be ``visible'' in future experiments. For example, the sterile neutrino required by the LSND result does not have any cosmological problem within these scenarios.
TL;DR: In this paper, the authors point out that if heavy metastable particles composing the dark matter of our galaxy are responsible for the ultra-high energy cosmic rays (UHECR), then the leading tidal stream of the Sagittarius dwarf galaxy could be detected through UHECRs.
Abstract: We point out that if heavy metastable particles composing the dark matter of our galaxy are responsible for the ultra-high energy cosmic rays (UHECR) then the leading tidal stream of the Sagittarius dwarf galaxy could be detected through UHECR. The signal would be an anisotropy in the UHECR flux smaller than the telltale anisotropy towards the galactic center that would first establish unstable dark matter as the origin of the UHECR.