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The Search for Neutrinoless Double Beta Decay. Tashi Parsons-Moss BNL NCSS 2006. β Decay and Weak Interaction. (A, Z) (A, Z + 1) + β - + e (1) (A, Z) (A, Z - 1) + β + + e (2) (A, Z) + e - (A, Z - 1) + e (3). Neutrinos. e , µ ,
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The Search for Neutrinoless Double Beta Decay Tashi Parsons-Moss BNL NCSS 2006
β Decay and Weak Interaction • (A, Z) (A, Z + 1) + β-+ e (1) • (A, Z) (A, Z - 1) + β++ e (2) • (A, Z) + e- (A, Z - 1) + e (3)
Neutrinos • e , µ , • 1930 – postulated by Pauli • 1956 – detected by Cowen et al. • Oscillations and Mass
Double Beta Decay • (A, Z) → (A, Z + 2) + 2e- + 2 (48Ca, 76Ge, 82Se, 96Zr, 100Mo, 116Cd, 128Te, 130Te, 150Nd, 238U) • (A, Z) → (A, Z + 2) + 2e- • (A, Z) → (A, Z + 2) + 2e- + 0(+0)
Possible Mechanisms of 0ββ decay • SUSY particles • Leptoquarks • Right-Handed weak interaction • Light of Heavy Majorana Neutrinos
0ββ Decay and Neutrino Mass • 3 Ranges of Mass sensitivity: • Quasi-Degenerate ~100-500 meV • Atmospheric neutrino oscillation results ~20-55 meV • Solar neutrino oscillation results ~2-5 meV
What’s the big deal? • = ? • Absolute mass scale for neutrinos • Leptogenesis • Weak Force • Grand Unified Theories
Challenges • Determining the dominant mechanism • Uncertainties in nuclear matrix elements • Limited resources, expense • Background, background, Background!!! • 2ββ peak • Cosmic radiation • Intrinsic background • Shielding and cryostat material
Heidelberg-Moscow • 71.7 Kg-y data • Controversial Results • Increased interest in quasi-degenerate 76Ge experiments
GENIUS (Germanium Nitrogen Underground Setup) • Assumes limiting background on HM from external sources • Array of 2.5 Kg p-type 86% enriched Ge crystals “naked” in LN2
Majorana • Assumes 68Ge within Ge detectors was limiting background in IGEX • 210 86% enriched, segmented n-type Ge crystals in ultra-pure electroformed Cu cryostats
MOON (Mo Observatory of Neutrinos) • Uses unique nuclear structure of 100Mo to combine 0ββ search and solar neutrino experiment • Modules of plastic fiber scintillators with thin layers Mo
Acknowledgements I would like to thank Richard Ferrieri and all of the TA’s, professors, students and supporters of the BNL Nuclear and Radiochemistry Summer School