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Double Beta Decay With 20-ton Metal Loaded Scintillators A Detector for DUSEL?

Double Beta Decay With 20-ton Metal Loaded Scintillators A Detector for DUSEL?. Frank Calaprice Princeton University Aldo Ianni LNGS. The Borexino Detector. 14 C ~ 3 x 10 -18 U/Th <10 -17 85 Kr ~ 0.35 cpd/ton Cleanliness level 25 MIL-STD 1246C. General Idea (Similar to SNO+).

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Double Beta Decay With 20-ton Metal Loaded Scintillators A Detector for DUSEL?

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  1. Double Beta Decay With 20-ton Metal Loaded ScintillatorsA Detector for DUSEL? Frank Calaprice Princeton University Aldo Ianni LNGS

  2. The Borexino Detector • 14C ~ 3 x 10-18 • U/Th <10-17 • 85Kr ~ 0.35 cpd/ton • Cleanliness level 25 MIL-STD 1246C

  3. General Idea (Similar to SNO+) • Use radiopurity MEASURED in the Borexino detector • Use preliminary data on Nd-loaded LS based on PC Goal: • Search for double beta decay with a 20ton-scale high purity LS detector • SNO+ proposal is for 1000 ton LS.

  4. Basic working assumptions: • T21/2 = 7 x 1018 yr • 50 meV neutrino mass (inverted hierarchy) • T1/2 = 1.2 x 1025 yr • Photon yield = 12000 / MeV (PC liquid scintillator) • QE = 0.35 (new high QE PMTs) • Coverage = 0.85 • Low radioactivity PMTs: ~ 30 mBq/PMT

  5. The Detector: basic idea FM

  6. Backgrounds: • PMTs + Steel Sphere ~ 40 Bq • 208Tl from nylon (<1ppt in Th) : • 0.861 MeV + 2.614 MeV ’s 12% BR • need to define FM • Radiopurity of nylon can be measured in CTF at ppt level or below. • Intrinsic Th in Scintillator: • Borexino 10-17 g/g gives ~ 1 c/yr around peak • Th coming with Nd ??? • Required ~ 10-15 gTh/gNd

  7. 1-kton SNO+ vs 20-ton scale detector: * Light absorption by Nd limits concentration **For comparison both detectors are assumed to have 50% PMT coverage.

  8. Natural abundance, 50 meV neutrino, 20-ton FM: 1 c/yr from nylon, ii) 1 c/yr from internal Th, iii) << 1 c/yr external Muon-induced activities above 3 MeV are short-lived and vetoed

  9. 50% 150Nd enrichment, 10 meV neutrino, 20-ton: • In 5 years the uncertainty in the measurement is 35%

  10. Breakdown of costs: • Add $3M for new purification system if LNGS • system is not used.

  11. Roadmap: • Measure radiopurity of nylon with present CTF • Preliminary tests of light propagation and energy resolution in small test chamber (~5 m3). • Rebuild CTF with Stainless Steel Sphere • Study Nd-loaded LS • Light propagation • Radiopurity • Energy resolution • Search for double beta decay at 50 meV sensitivity with CTF system. • Build larger (~50 ton LS?) system with optimum resolution/background for 10 meV at DUSEL?

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