Development of a Liquid Scintillator and of Data ... - Borexino - Infn

2.1 Physics Goals
be detected in 300 tons of scintillator [Ali99]. This will be mainly due to CC scattering
of electron antineutrinos on protons Ô Ò (threshold 1.8 MeV), with an additional
contribution from NC scattering of neutrinos on carbon ÜÜ (threshold
15.1 MeV). The potential of the BOREXINO detector for Supernova neutrino detection
is discussed in more detail in [Cad00].
- The uranium and thorium content in the earth’s crust can be determined by measuring
the antineutrinos from their decay chains via inverse beta decay Ô Ò (threshold
1.8 MeV). This will give important geophysical information on the heat generation inside
the earth [Rag98]. The estimated geophysical antineutrino event rate in BOREXINO
is 10 events per year.
- Nuclear power reactors are strong sources of electron antineutrinos. By measuring the
rate of antineutrinos from the nuclear power plants in Europe it is possible to perform a
long-baseline neutrino oscillation search to probe the LMA solution of the MSW effect
[Sch99b]. The nuclear reactors which dominate the flux are at a distance of km to
Gran Sasso, as Italy itself has no nuclear power reactors. Since the distances to the reactors
are known, and the fuel composition and operating cycle of the reactors can also be
known very well, the antineutrino event rates and the positron spectrum in BOREXINO
can be calculated with an uncertainty less than 3 %. The expected reactor antineutrino
event rate in 300 tons of scintillator is events per year. For the LMA solution
the neutrino flux would be suppressed by % . The expected background due to
accidental coincidences is less than 1 event per year.
- The magnetic moment of the electron neutrino can be determined by using a strong
artificial neutrino source, e.g. Cr or Sr, that allows one to measure the shape of the
neutrino energy spectrum [Ian98, Ian99a, Ian99b]. The source will be placed in a tunnel
directly below the BOREXINO tank.
- It is also possible to load the scintillator with a double beta unstable isotope, e.g. Xe,
and search for neutrinoless double beta decay [Cac00, Bel01], which is allowed only
if the neutrino is a massive Majorana particle. A different approach uses scintillating
crystals doped with the double beta instable isotope, namely CdWO, which would
be placed inside the scintillator. In this case, the liquid scintillator would serve only as a
veto detector [Bel00]. The limit on Ì ¬ reachable with 65 kg of CdWO crystals
in the CTF is a, corresponding to Ñ eV. With 1000 kg CdWO in
BOREXINO a limit for Ñ eV could be reached.
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