1. 0νDBD Experimental Review and 136 Xe With HP Gas at CJPL 季向 东

2. Outline  Overview about the field: US DOE/NSF review  PandaX III proposal for CJPL

3. Two Types of Double Beta Decay 2  mode: a conventional 2 nd order process in Standard Model 3 Observation of  : Majorana neutrino Neutrino mass scale Lepton number violation

4. Double beta nuclei and decay spectrum

5. US Report on Neutrinoless DBD, April 24, 2014  Charged by DOE and NSF  Committee Chair (R. McKeown)  Members: Zheng-tian Lu, Calaprice, Haxton, Vigdor, Scholberg, Hertzog, Cirigliano, Fisher, Shutt, Langanke, Geesaman, Sobel, Greene, Hardy  Experiments: CUORE, Majorana, Gerda, EXO-200, nEXO, NEXT, KamLAND-Zen, SuperNEMO, SNO+, etc

6. Some details:  Importance of pursuing a second generation NLDBD:  Importance of current R&D

7. 7 T 1/2 0νββ > 1.1∙10 25 yr (90%CL) < 190 – 450 meV Average T 1/2 0νββ sensitivity: 1.9∙10 25 yr J.B.Albert et al. (EXO-200) arXiv:1402.6956 (27 Feb 2014) A. Gando et al. (KamLAND-ZEN) PRL 110 (2013) 062502 M. Agostini et al. (GERDA) PRL 111 (2013) 122503 Comparison of 0  Measurements Old EXO-200 limit Old EXO-200 sensitivity M. Auger et al. (EXO-200) PRL 109 (2012) 032505

8. Main points  The DBD sensitivity depends on the mass. Different isotopes have similar sensitivity when masses are the same  We need to go for large mass!  The leading experiments are at 100kg scale.  We must consider only 100kg scale experiment

9. The Neutrino Mass Scale and Hierarchy 9 <2.3 eV <0.3 eV “Normal hierarchy” “Inverted hierarchy” < 0.28- 1.5 eV Cosmology WMAP + SN + Galaxy clustering (measures sum of neutrino mass) Measures electron neutrino mass Measures effective Majorana neutrino mass

10. Effective Neutrino mass

11. Why Xe136  Large Q value, 2.458 MeV  Relatively easy to purify  Easy to get large quantities (1 ton)  Can have high-energy resolution  Can be scaled easily.  Have tracking capability in gaseous phase.  Together with Ge and Te, becoming the most promising agent.

12. Three existing experiments with Xe136  EXO-200, nEXO  Kamland-Zen  Next100

13. EXO200  200kg Xe, 80% Xe136  100kg in the fiducial  80kg Xe136 for setting limit  Reading both light (APD) and charge (Wires)  Energy resolution 1.7%, meaning a 1σ window 40 keV  2458 ± 40 keV

14. First 0ν result

15. Second paper

16.  Second paper, 104 kg yr, about 3-4 times increase in data  39 events in the 2σ E region, 31 are background  Th232, 16  U238, 8  Xe137, 7

17. Problems with EXO and nEXO

18. KamLAND-Zen  1.8m radius mini-balloon filled with LS loaded with 600kg 136 Xe (90% pure).  Fiducial mass 434 kg and overall background 24 events/year (2νββdecay + 214 Bi)  Strength : leading expt. before 2020, suppressing γ background through LS, reducing background by purification, cosmic ray suppression by triple coincidence (µnγ), easily to scale.  Challenges: Energy resolution (9.5%FWHM); background 110m Ag, radioactivity in balloon, demonstrate uniqueness of the signal, etc.

19. NEXT  Use high-pressure gas TPC in Canfranc UL in Spain.  Tracking: SiPMs coated with WLS  Energy and timing: PMT  10kg planned for 2015  100kg planned for 2016  Strength: both energy and tracks, Gas circulation and purifciation, Verifying possible non-null signal…  Problems: Large pressure vessel must be radiopure, dependability of the event structure…

20. Schedule of the current generation

21. Next generation

22. Future Guideline

23. PandaX III: 136 Xe 0νDBD experiment with HP Gas

24. Energy resolution  Using high-pressure xenon gas (6- 15 bar), room or lower temp  Advantages  High-energy resolution

25. Tracks:”zero” background  Gas TPC provides excellent tracks for DBD events

26. Discrimination ability  Through MC simulations, one finds the following tracking discrimination:  For physical events acceptance rate is 40%  For Tl208 and Bi214, the discrimination ability is from 20 to 1000.  This is much better than order of 1!

27. High-purity vessel  One needs to have a very high purity vessel  Cu is the standard  However, one can also use Ni- Alloy.

28. Staged plan  200 kg  Test  Discovery potential  modules  1 ton  5 200kg modules

29. 200kg module  Ionization and light

30. Readout Two Important requirements: tracking and energy resolution Simplicity! Two plans: 1. Mircomegas (MM): jianglai 2. CMOS (future): Xianming

31. MM  Existing technology  Can do both tracking and energy  Has been tested under high- pressure context in a small detector  Best energy resolution is about 1% FWHM

32. Tracking with MM (NEXT-MM)

33. Energy resolution

34. Ionization  Large area tracking using ThGEM and MicroMEGA with ASIC readout  Tracking size for 1MeV electron, 10- 20cm  Drifting distance 50cm  Adding other gases to increasing drifting speed? Less diffusion

35. Prototype R&D at SJTU  1.3 meter long, 70cm D  6-15 bar  Gas system and vessel done by March, 2015  Testing throughout the year  Ordering MM, different types

36. 200kg module  Starting building 200kg module in 2015  Deployment in 2016?  TPC + electronics  200 kg xenon  Shield (10mD water tank) etc