INIITIAL POINTS: –LNGS muon Angular Distribution / MACRO / - [1] –Cylindrical symmetry PMT placement Muon Energy – 17.5 GeV Optical Photon Energy – 2–5 eV [ nm] Photocathode Radius – 20 cm Photocathode Quantum Efficiency – 0.15 Water Transparency – 10 m Tyvek Reflactivity – [2] PMT Number - 45 – 150 [ 0.3 – 1.0 % ] Cherenkov photons – 300 photon/cm MaGe frame

SETUP USED IN CALCULATIONS

EVERYWHERE ARE PRESENTED DISTRIBUTIONS OF VALUES

MUON INPUT POINT TO WATER TANK

FIRST PMT HIT

PMT DISTRIBUTION

PMT HITS TIME HIGHT DISTRIBUTION r

COUNT RATE IN WATER TANK

RESULTS By taking 1 and more fired PMT as muon trigger we will have 45 PMT give reduction factor of background ~ 170 / 99.41% / 110 PMT give reduction factor of background ~ 430/ 99.77% / Input count rate is ~ 3500 Hz for N_pmt >0 –Such reduction input External Gammas Background – at level 10^-3 cpy/kg/keV

REFERENCES [1] S.Ahlen et al.,”Muon Astronomy With the Macro detector”, App.J. 412(1993) [2] hep-ex/ “ A new Ge-76 Double Beta decay Experiment at LNGS” [3] C.Arpesella, Nucl.Phys.( Proc. Suppl. ) A 28 (1992)