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The Search for Neutrinoless Double Beta Decay

This presentation by Tashi Parsons-Moss at BNL NCSS 2006 delves into the complexities of neutrinoless double beta decay (0νββ) and its significance in understanding neutrino mass and the fundamental workings of the weak interaction. It covers the history of neutrinos, the proposed mechanisms for 0νββ decay, recent experimental results, and the challenges faced in detection, including issues related to nuclear matrix elements and background noise. Special focus is given to promising experimental setups, such as GENIUS and MOON, and their roles in the ongoing search for this elusive process.

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The Search for Neutrinoless Double Beta Decay

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  1. The Search for Neutrinoless Double Beta Decay Tashi Parsons-Moss BNL NCSS 2006

  2. 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)

  3. Neutrinos • e , µ ,  • 1930 – postulated by Pauli • 1956 – detected by Cowen et al. • Oscillations and Mass

  4. 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)

  5. Possible Mechanisms of 0ββ decay • SUSY particles • Leptoquarks • Right-Handed weak interaction • Light of Heavy Majorana Neutrinos

  6. 0ββ 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

  7. What’s the big deal? •  =  ? • Absolute mass scale for neutrinos • Leptogenesis • Weak Force • Grand Unified Theories

  8. Challenges • Determining the dominant mechanism • Uncertainties in nuclear matrix elements • Limited resources, expense • Background, background, Background!!! • 2ββ peak • Cosmic radiation • Intrinsic background • Shielding and cryostat material

  9. Recent 0ββ results

  10. Recent claim of 0ββ detection

  11. Heidelberg-Moscow • 71.7 Kg-y data • Controversial Results • Increased interest in quasi-degenerate 76Ge experiments

  12. 0ββ Proposals

  13. 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

  14. 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

  15. Majorana

  16. MOON (Mo Observatory of Neutrinos) • Uses unique nuclear structure of 100Mo to combine 0ββ search and solar neutrino experiment • Modules of plastic fiber scintillators with thin layers Mo

  17. MOON

  18. 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

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