Investigation on light dark matter

Some extensions of the Standard Model provide Dark Matter candidate particles with sub-GeV mass. These Light Dark Matter particles have been considered for example in Warm Dark Matter scenarios (e.g. the keV scale sterile neutrino, axino or gravitino). Moreover MeV scale DM candidates have been proposed in supersymmetric models and as source of the 511 keV line from the Galactic center. In this paper the possibility of direct detection of a Light Dark Matter candidate is investigated considering the inelastic scattering processes on the electron or on the nucleus targets. Some theoretical arguments are developed and related phenomenological aspects are discussed. Allowed volumes and regions for the characteristic phenomenological parameters of the considered scenarios are derived from the DAMA/NaI annual modulation data

Dark Matter search

Main arguments on the Dark Matter particle direct detection approach are addressed on the basis of the work and of the results of the about 100 kg highly radiopure NaI(Tl) DAMA experiment (DAMA/NaI), which has been operative at the Gran Sasso National Laboratory of the I.N.F.N. for more than one decade, including the preparation. The effectiveness of the WIMP model independent annual modulation signature is pointed out by discussing the results obtained over 7 annual cycles (107731 kg day total exposure); the WIMP presence in the galactic halo is strongly supported at 6.3 standard deviation C.L. The complexity of the corollary model dependent quests for a candidate particle is also addressed and several of the many possible scenarios are examined

Results from DAMA/NaI and perspectives for DAMA/LIBRA

The about 100 kg highly radiopure NaI(Tl) set-up of the DAMA project (DAMA/NaI) took data over seven annual cycles up to July 2002 and has achieved results on various rare processes. Its main aim has actually been the exploitation of the model independent WIMP annual modulation signature. After this conference the total exposure, collected during the seven annual cycles, was released. This cumulative exposure (107731 kg day) has given a model independent evidence for the presence of a Dark Matter particle component in the galactic halo at 6.3 sigma C.L.; this main result is summarised here. Some of the many possible corollary model dependent quests for the candidate particle are mentioned. At present, after about five years of new developments, a second generation low background set-up (DAMA/LIBRA with a mass of about 250 kg NaI(Tl)) was built and is taking data since March 2003. New R&D efforts toward a possible NaI(Tl) ton set-up, we proposed in 1996, have been funded and started in 2003

DAMA/NaI results

The DAMA/NaI set-up of the DAMA experiment has been operative during seven annual cycles and has investigated several rare processes. In particular, it has been realised in order to investigate the model independent annual modulation signature for Dark Matter particles in the galactic halo. With the total exposure collected in the seven annual cycles (107731 kg day) a model independent evidence for the presence of a Dark Matter particle component in the galactic halo has been pointed out at 6.3 sigma C.L.. Some of the many possible corollary model dependent quests for the candidate particle have been presented as well

New search for correlated e+e- pairs in the alpha decay of 241Am

A new search for production of correlated e+e- pairs in the alpha decay of 241Am has been carried out deep underground at the Gran Sasso National Laboratory of the I.N.F.N. by using pairs of NaI(Tl) detectors of the DAMA/LIBRA set-up. The experimental data show an excess of double coincidences of events with energy around 511 keV in faced pairs of detectors, which are not explained by known side reactions. This measured excess gives a relative activity lambda = (4.70 \pm 0.63) \times 10^{-9} for the Internal Pair Production (IPP) with respect to alpha decay of 241Am; this value is of the same order of magnitude as previous determinations. In a conservative approach the upper limit lambda < 5.5 \times 10^{-9} (90% C.L.) can be derived. It is worth noting that this is the first result on IPP obtained in an underground experiment, and that the lambda value obtained in the present work is independent on the live-time estimate