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Scientific Report 2007-2009<br />
Particle physics<br />
1.2.1 Neutrino Physics<br />
In the field of fundamental particle physics the neutrino has become more and more important<br />
in the last few years, since the discovery of its mass. In particular, the ultimate nature of the<br />
neutrino (being a Dirac or a Majorana particle) plays a crucial role not only in neutrino physics,<br />
but in the overall framework of fundamental particle interactions and in cosmology. The only<br />
way to disentangle its ultimate nature is to search for the so-called Neutrinoless Double Beta<br />
Decay (0ν2β). A group of the Department has participated in Cuoricino experiment and it is<br />
now fully engaged in the preparation of CUORE experiment at LNGS [P25]. CUORE is a 1<br />
ton array of 988 crystals of TeO 2 that will be kept in a dilution refrigerator at a temperature<br />
of 10mK. By using the spectacular energy resolution in the measurement of the heat released<br />
by nuclear processes occurring inside the crystals, this experiment will cover an half-life of 130 Te<br />
for the (0ν2β) up to 10 26 y. The Roma group has taken, amongst others, the responsibility of<br />
procuring the crystals (done in RP China by SICCAS), by developing the entire chain of QC/QA<br />
of the crystal production that involves ICP-MS and Ge measurements at all levels and the final<br />
acceptance tests. A follow up of this activity has been the award of an ERC-AdG to one of<br />
the group member for a demonstrator for the next level of background reduction in this kind<br />
of experiments thanks to the combined read-out of heat and scintillation light in new materials<br />
(project LUCIFER).<br />
On the sector of neutrino oscillations, a small but significative participation of the Department<br />
is in the OPERA experiment that exploits the CERN-LNGS neutrino beam. The search for ν τ<br />
appearance will close the 3-neutrino picture of the oscillations and and is based on the emulsion<br />
scanning [P26], a technique which has seen our Department on the front line, since the antiproton<br />
search in cosmic rays by the E. Amaldi group in the ’50s of the last century.<br />
1.2.2 Dark Matter<br />
Dark Matter (DM) is an hot subject nowadays. This elusive component of our Universe is searched<br />
at colliders, in space and underground. A group of this Department is active in the DAMA [P28]<br />
experiment at LNGS. This experiment has the aim of performing a direct detection of DM particles<br />
present in the galactic halo by using the annual modulation signature. It is based on ultra-pure,<br />
very low background NaI scintillator and thanks to its large mass has integrated an exposure in<br />
excess of 0.50 ton×y (the highest of this kind of experiments). The results, worldwide known,<br />
is an intriguing, statistically significant, presence of a modulation that could be explained by<br />
DM particles interacting with the detector. Improvements to the experiment (better quantum<br />
efficiency photomultiplier), with a crucial involvement, of the Roma group are being made.<br />
AMS [P29] will soon fly to space and amongst other field of investigations will be sensitive to<br />
the product of annihilation of DM particles.<br />
1.2.3 Gravitational Waves<br />
Gravitational waves (GW) are space time-ripples such that the distance between free masses will<br />
alternately decrease and increase during their transit out of phase in two perpendicular directions.<br />
The VIRGO detector consists of a laser interferometer with two orthogonal arms each 3 km long.<br />
The sensitivity extends from 10 to 10000 Hz with a typical value of h ∼ 10 −21 for the amplitude<br />
of the GW (see Fig. 4).<br />
The VIRGO group of Rome plays a crucial role in VIRGO [P30]. The group mainly contributes<br />
to VIRGO:<br />
• by designing , constructing and setting up the giant interferometric apparatus,<br />
• by defining the strategy for the analysis of the collected data and developing the software<br />
needed to attain the scientific target of the detection of the gravitational waves<br />
<strong>Sapienza</strong> Università di Roma 106 Dipartimento di Fisica