- Conference date: 30 Jul-3 Aug 2001
- Location: Berkeley. California (USA)
The Borexino experiment, aimed at measuring the solar neutrinos, is currently under construction at the underground National Laboratories of Gran Sasso in central Italy. The Gran Sasso underground labs are located below 1,400 m of rocks. The equivalent shielding for cosmic rays is 3,800 m of water equivalent, and the residual muon flux is ∼1/m2/h. The number of muons crossing the Borexino detector is 10,000/day, to be compared with the number of neutrino events in the central fiducial detector of ∼10/day. A muon veto sub-detector was designed with the purpose of reducing background from muons and cosmogenic nuclides below 1 event per day in the spectral region of the equivalent energy between 250 and 800 keV, where the signal from the neutrinos is expected. The muon veto sub-detector consists of two separate parts. Four hundred photomultiplier tubes measure the scintillation photons and the Cerenkov photons produced by muons either in the 300 tons of scintillator or in the 1000 tons of pseudocumene buffer. Two hundred photomultiplier tubes measure the Cerenkov photons produced by muons in the water shield surrounding the pseudocumene buffer. The paper presents an overview of the muon background in Borexino and an estimate of the background reduction which is expected to be produced by the muon veto. A full discussion of the experimental apparatus is provided as well.
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