1. Future of DM Detection Mark Boulay, Los Alamos Mark Boulay CLEAN: A Detector for Dark Matter and Low-Energy Solar ’s Liquid neon as a target for dark matter and neutrino interactions (the CLEAN experiment) Position reconstruction/backgrounds in CLEAN Experimental sensitivity Dependence on optical and detector properties Test Bench at Yale (pico-CLEAN) arxiv.org:/nucl-ex/0410025 arxiv.org:/astro-ph/0402007 Idea for Dark Matter with LAr Favorable review from SNOLab EAC

2. Future of DM Detection Mark Boulay, Los Alamos GEANT4 MC of scintillation events in CLEAN 15000 photons/MeV 60 cm Rayleigh scattering at 80 nm ~75% coverage, 1842 PMTs 15% QE 80 nm shifted to blue for detection 250 keV electron at z=250 cm CLEAN R&D Collaboration Boston University Ed Kearns Los Alamos National Laboratory Mark Boulay, Andrew Hime, Jeff Lidgard, Dongming Mei NIST Kevin Coakley Yale University Hugh Lippincott, Matthew Harrison, Benjamin Jorns, Dan McKinsey, James Nikkel

3. Future of DM Detection Mark Boulay, Los Alamos Scintillation in liquid neon Ionizing radiation leads to formation of dimers in Neon Singlet and triplet states are produced, decay times are ~3 ns (singlet, prompt) and ~2.9  s (triplet, late) Amount of prompt and late components depends on particle: Electron recoils: prompt:late 1:3 Nuclear recoils: mostly prompt (being measured at Yale) Allows discrimination between electron recoils (neutrinos, beta+gamma) from nuclear recoils (WIMPs, neutrons) This discrimination can be achieved with a simple detector design (no need for electron drift), possible advantage

4. Future of DM Detection Mark Boulay, Los Alamos Backgrounds, backgrounds, backgrounds The CLEAN approach: With material selection, clean target, sufficient depth, and appropriate cuts, provide a signal region which will contain only signal events (solar nu’s and WIMPs) (basically the SNO approach) Internal radioactivity->clean materials External radioactivity->reconstruction cuts Neutrino vs WIMP separation->timing PSD interesting aside: SNO NC detection corresponds to 10 -6 events/kg/day

5. Future of DM Detection Mark Boulay, Los Alamos Time-of-flight (TOF) information for vertex reconstruction T res = T pmt –T fit –d pmt /v photon Scattering introduces position dependence to T res, and broadens the distribution, but this info is still useful… 2d pdf in T res, R event

6. Future of DM Detection Mark Boulay, Los Alamos Likelihood surface using TOF information Likelihood surface (in detector x,y coordinates) for event at x = 294 cm, near PMT Deep minimum near event location In likelihood surface can be used to precisely locate event, improve Background rejection X2 improvement in position resolution with TOF information! ->PMT data can be used for PMT background rejection and WIMP/e discrimination

7. Future of DM Detection Mark Boulay, Los Alamos Expected physics signals in CLEAN

8. Future of DM Detection Mark Boulay, Los Alamos External backgrounds after fiducial cut “sample” 300 cm detector with 125 cm fiducial cut Commercially available ultra-low background PMT Glass 30 ppb U, Th 60 ppm K

9. Future of DM Detection Mark Boulay, Los Alamos Distinguishing WIMPs from electrons Time distribution of PMT hits Are different for electron recoils (neutrinos) and nuclear recoils (WIMPs) Ratio of prompt/late hits can separate (statistically) electron and nuclear recoils ->From simulation, limit on WIMP events is ~1 events/year in solar neutrino background for 125 cm volume of Neon PMT TOF spectra prompt ratios Expect improvement

10. Future of DM Detection Mark Boulay, Los Alamos Sensitivity to WIMPs and neutrinos with liquid neon ~10 -46 WIMP sensitivity pp statistical uncertainty Detector size 300 cm <1% 1 year livetime

11. Future of DM Detection Mark Boulay, Los Alamos Sensitivity to PMT backgrounds +/- factor of 10 on PMT activity

12. Future of DM Detection Mark Boulay, Los Alamos Dependence on optical parameters Quenching factor Scintillation time Scintillation yield Rayleigh scattering

13. Future of DM Detection Mark Boulay, Los Alamos

14. Future of DM Detection Mark Boulay, Los Alamos DD neutron generator at Yale

15. Future of DM Detection Mark Boulay, Los Alamos pico-CLEAN at Yale for scintillation measurements

16. Future of DM Detection Mark Boulay, Los Alamos Noble Gas Purification System at LANL

17. Future of DM Detection Mark Boulay, Los Alamos Summary of potential advantages of Liquid Neon In principle can be CLEANed to levels needed for simultaneous Dark Matter/pp neutrino experiment Spherical target volume can be scaled to large target masses needed for next-generation sensitivity Spherical (SNO-like) design allows for fiducialization and hence mitigation of external source backgrounds Intrinsic pulse shape discrimination (e - vs nuclear recoils) allows for a “simple”, single-detector-system design pp neutrino sensitivity should lead to a positive result Can be complementary to WIMP search with heavier target

18. Future of DM Detection Mark Boulay, Los Alamos scintillation pulse- shape analysis for discrimination of e- vs nuclear recoils -> no electron-drift http://arxiv.org/astro-ph/0411358 DEAP : Dark-matter Experiment with Argon PSD

19. Future of DM Detection Mark Boulay, Los Alamos DM with liquid argon PSD (DEAP) 6 pe/keV for 75% coverage, with 1500 Hz PMT noise Backgrounds from Ham. R9288 (approx. 70 mBq/PMT) 5 ns PMT resolution 20% photon detection efficiency 100 ns trigger window sets T 0 F prompt = Prompt hits(100 ns)/Total hits(15  s) ~2 kg Ar with 10 keV ee threshold (60 pe) Dominant backgrounds assuming proper shielding, depth, and clean construction.

20. Future of DM Detection Mark Boulay, Los Alamos Effect of Form Factor Suppression Integrated rates above threshold with 25% quenching

21. Future of DM Detection Mark Boulay, Los Alamos Background rejection with LAr (simulation) From simulation, rejection > 10 8 @ 10 keV (Goal for SuperCDMS is 10 8 from R. Schnee talk on Thurs.) 10 8 simulated e-’s 100 simulated WIMPs

22. Future of DM Detection Mark Boulay, Los Alamos DM Sensitivity with LAr, LNe with 1-year exposure

23. Future of DM Detection Mark Boulay, Los Alamos DEAP at LANL LAr cryostat under construction at LANL Test PMTs in LAr for timing, efficiency, stability, noise rate, pulse shape (ionic afterpulsing) Build small 4  detector with pulse digitization to demonstrate PSD Construct shielding and move U/G to WIPP or SNOLab for WIMP search Design larger-scale (100+ kg) experiment

24. Future of DM Detection Mark Boulay, Los Alamos Conclusions PSD in LAr, LNe looks promising due to long triplet time (microsec) A Liquid neon experiment may be a relatively simple DM experiment with good sensitivity, and has sensitivity to solar neutrinos (positive physics result even if no WIMP signal is seen). -> Form factors and effect of energy thresholds, competes with large-A coherence, so that neon is within X6 of xenon, and argon is comparable to xenon for reasonable thresholds pico-CLEAN in progress at Yale for Ne scintillation parameters needed to evaluate DM capability Potential for PSD in liquid argon dedicated-DM experiment -in progress at LANL (DEAP)