, University of Florida OscSNS - proposal for neutrino experiment at ORNL SNS facility 1 of 19
Outline ORNL SNS facility Neutrino production at SNS Neutrino detection at SNS Event reconstruction and particle IDs Event rates and sensitivity Conclusion 2 of 19
Spallation Neutron Source 1 GeV proton beam on Hg target production of spallation neutrons 3 of 19
Neutrino production at SNS 11.6% p produce π + π + + +ν ( 100% π + + + decay e +ν e +ν ) 99.3% DAR 0.7% DIF + ( ~100% DAR) 4 of 19
Timing structure With a simple beam-on timing cut one can obtain a fairly pure ν sample (14% contamination of ν and ν e each) 5 of 19
Total neutrino flux - Well-known neutrino spectra ν with E = 29.8 MeV - Mono-energetic - ν, ν e end-point E = 52.8 MeV 6 of 19
Neutrino detection MiniBooNE-type detector - 60 m upstream from the Hg target; - 12-m diameter sphere (fiducial = 10 m); - filled with 800 t of mineral oil CH2( fiducial = 450 t) + ~30 kg of butyl-pbd scintillator; - 3502 phototubes: 3262 in detector (25% coverage) and 240 in veto region; - buried under 10 ft of dirt to suppress cosmic rays and beam-induced neutrons. 7 of 19
Geant4 beam simulation proton beamline interaction tracks world volume detector target hall 8 of 19
Neutrino flux in the detector (50 M POT) ν ν e ν ν e 9 of 19
lifetime in various materials Material Be Fe Hg Lifetime, ns (experiment) 2162.1 ± 2.0 206.0 ± 1.0 76.2 ± 1.5 Lifetime, ns (QGSPBERT) 2161.0 205.9 72.3 9 of 19
Geant4 detector simulation 40 MeV positron Done: - preliminary simplified geometry (tank, veto, PMTs, oil); - optical model parameters (refractive index, absorption length, etc) taken from other experiments (MiniBooNE) - Cherenkov and scintillation (slow and fast components) light propagation (LSND) Needs to be done: - simulate the phototube and electronic response - add more event types 10 of 19
Event reconstruction and particle IDs Maximum likelihood algorithm (charge and time info from PMTs) Particle topology Electron (fuzzy ring) Muon (sharp ring) through-going stopping 11 of 19
Cross-section measurements 800 ton detector (6 m radius) 5m fiducial volume 50% detector efficiency 1 year run time 1) ν C ν C 2) ν * e C e N 3) ν e e ν ee measured by KARMEN experiment but with only 86 events and 20% error OscSNS expects ~1,300 events Main channel for sterile neutrinos <5% error can be used to normalize total neutrino flux OscSNS expects ~4,600 events measured by LSND experiment OscSNS expects but with only 191 events and 17% error ~1,300 events 100,000 events from Super-K (unknown flux) 12 of 19
Event rates per year 800 ton detector (6 m radius), 5m fiducial volume, 50% detector efficiency, 10% flux uncertainty, 1 year run time 13 of 19
Background suppression Short pulsed beam: cosmic-ray background rejection 60 Hz, 695 ns pulse-width (500 ns pulse-width was achieved) 6% p produce π π +ν e +ν ν ν (0.5% π decay + ν e (24.6% decay e 100% DIF) < 9 10 4 100% DAR) reduction as ( expect MC becomes more advanced) 14 of 19
More background suppression DIF negative mesons are boosted in forward direction, so neutrinos are mostly emitted in forward direction Time spectrum of ν e Slow decay of Fast decay of Time-cut at 1000 ns can eliminate ν e in low-z materials(be,al); in high-z materials(hg,pb,fe); from decay in Hg,Pb... 15 of 19
Appearance sensitivity Confidence level curves forν ν e oscillations 16 of 19
Disappearance sensitivity Confidence level curves for ν ν s oscillations 17 of 19
Conclusion Neutrino environment at SNS facility offers a unique opportunity for both oscillation- and cross-section type of experiments: - background suppression - well-known neutrino flux - free source of neutrinos 18 of 19
OscSNS collaboration Current: - U Alabama - U Florida - LANL - Purdue U Calumet - U South Carolina - ORNL / U Tennessee Submitted white-paper to DoE(nuclear and high-energy) and NSF more information: http://physics.calumet.purdue.edu/~oscsns 19 of 19
Danke Grazie Σε ευχαριστώ Thank you Tak Спасибо Merci धन व द Gracias Obrigado