Comparing Large Underground Neutrino Detector Technologies: Liquid Argon, Liquid Scintillator, and Water Cherenkov

1. Comparing Large Underground Neutrino Detector Technologies:Liquid Argon, Liquid Scintillator, and Water Cherenkov John G. Learned University of Hawaii at ANT09, Hawaii A personal view, based upon experience with all three technologies. Good source papers: “Report on the Depth Requirements for a Massive Detector at Homestake”, arXiv:0907.4183v2; Large underground, liquid based detectors for astro-particle physics in Europe: scientific case and prospects”, arXiv:0705.0116v2

2. The three detectors in the LAGUNA study 1 vertical John Learned @ ANT09

3. Material Properties All three media are readily available in industrial quantities. John Learned @ ANT09

4. Water Cherenkov • Cheapest target medium (but not negligible with filtering and dopants) • Only route to megaton instruments • Well proven technology (IMB, Kam, SK) • Excellent for mu/e separation ~1 GeV. • Electron scattering for solar nus. • Threshold above ~4 MeV => no geonus or n-p captures. n detection needs Gd. • No complex event topologies. John Learned @ ANT09

5. Liquid Scintillation Detectors • Hi resolution, low threshold (<MeV) • Technology well developed (50 years, plus Borexino, KamLAND and soon SNO+) • Excellent for anti-neutrino detection by inverse beta decay. • Liquid too expensive beyond ~100kT. • New recognition: GeV neutrino physics too. John Learned @ ANT09

6. Liquid Argon TPC Detectors • Bubble chamber-like imaging, detailed event topology, with few mm resolution. • Developed over 30 years, and now being applied in 600 ton Icarus in Gran Sasso. • No free protons for nucleon decay or inverse beta studies. • Only detector for potential discrimination of e+ from e- at neutrino factory. John Learned @ ANT09

7. Energy Range of Interest Large Underground Detectors Accelerator Neutrinos John Learned @ ANT09

8. Liquid Treatment • All three require special facilities, all expensive and a bit hard to compare. • Lesson of past: do great job on first fill into superclean detector, have radon tight system, and do not have to recirculate much or at all. John Learned @ ANT09

9. Muon Rates for 100 kiloton Detectors at Homestake John Learned @ ANT09

10. Depth Requirements • All depends upon physics goals… • Also depends upon detector size… external backgrounds (eg. from muon showers in rock); worst for small instruments. Big detectors take hit near periphery. • Great depth only needed for MeV measurements (geonus, low end of solar). • PDK, accelerator studies, atm nus, SN, DSNB all can be done at much less depth… exact depth arguable depending upon technique and physics. John Learned @ ANT09

11. Rough Graphical Representation of Depth Requirements Many caveats required, but trend is correct... jgl opinion Long Baseline ~1GeV ν’s Nucleon Decay Supernova ~No Background Reactors Diffuse SN Neutrinos Geo-Neutrinos John Learned @ ANT09

12. Nucleon Decay Predictions John Learned @ ANT09

13. Nucleon Decay L Ar LS H2O 43/2.25 1.0 x 1035 The e+π0 estimate for LENA is based upon new fitting methods. John Learned @ ANT09

14. Supernova Rates John Learned @ ANT09

15. Diffuse Supernova Neutrino Background Better low energy atmospheric neutrino flux calculations needed. John Learned @ ANT09

16. Physics Summary Comparison Chart John Learned @ ANT09

17. LAGUNA Seems to be on the map! Who will win? Plus Japan (HyperK). How will DUSEL fit into this picture? John Learned @ ANT09

18. Bottom Line • Each has strengths • Long range: LAr wins for detailed neutrino physics in LBL, tho nice anytime • Great sizes (megaton): H2O wins • Low energies: Liquid Scint wins (particularly for geonus) • Cost/vol hierarchy: LAr:LS:H2O • Readiness: LS & H2O > LAr • I like them all!! John Learned @ ANT09