1. Future Accelerator Based Neutrino Experiments Takashi Kobayashi Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization (KEK) Aug.22,2011 Lomonosov Conf Moscow

2. Standard picture of 3 flavor mixing 2 e   Flavor eigenstates m1m1 m2m2 m3m3 Mass eigenstates 6 independent parameters govern oscillation  12,  23,  13,   m 12 2,  m 23 2,  m 13 2 Atm/AccAcc/ReactorSol/Reactor 2  m ij =m i 2 -m j 2 Pontecorvo-Maki-Nakagawa-Sakata Matrix (CKM matrix in lepton sector)

3. Present knowledge (before June, 2011) 3 OR 1 2 3 Which?? e ?? Big diff from KM matrix  unkown Sol/Reactor Atm/Acc

4. Indications of large  13 4 T2K 6event obs. 1.5 BG exp’ed 2.5  (June 13,2011) MINOS 62event obs. 49.5 BG exp’ed 1.7  (June 24,2011)

5. New results on  disappearance  T2K released the first disappearance result  Consistent with MINOS & SK results  MINOS data indicates slight tension between  and anti-  5

6. What’s next?  Immediate issues with on-going experiments  EXPERIMENTALLY establish non-zero  13 as soon as possible  Precise measurement of  23,  m 23 (both for  and anti-  ), whether maximal mixing or not?  Next most important goal: CPV  CP is violated/conserved in neutrino?  What is the mechanism of violation? PMNS-type “standard” scenario or anything exotic origin? 6

7. Toward one of big goals of particle physics: Origin of Matter-dominated Unvierse Sakhalov’s 3 conditions  Baryon number violation  Proton decay  CP violation  Quark CPV seems not sufficient  Lepton CPV may contribute  Non-equilibulium 7

8. 88   e appearance and CPV CPV effect (sin  12 ~0.5, sin  23 ~0.7, sin   <0.2) Unknown! CPV Sol term The size of  13 decide future dir.!  e appearance is golden mode for CPV IF e appearance exist  No CPV effect in disappearance  Only  beam is presently technically available  Small leading CPC term  Large CPV effect ( ⇔  app.)

9. Expected CPV (&matter) effects (w/ “standard” PMNS framework)  ~20% CPV effect at sin 2 2  13 =0.1 w/ sin  CP =1 (max. vio.) at 1 st peak  To detect CPV >3  for sin  >0.2 (Asym=4%)  O(10k) events necessary  Much higher statistics is necessary  >MW proton & huge detector mandatory  CPV asymmetry get smaller for larger  13  Severer requirement on systematic error  Matter effect becomes comparable (@295km) or dominant (2300km) at 1 st peak (  potential to determine mass hierarchy )  CPV asymmetry get much larger for 2 nd peak  Matter effect become small correction 9 T2K 90% region 1 st peak @ 2300km (4.65GeV)1 st peak @ 295km (0.6GeV)2 nd peak @ 2300km (1.6GeV) Pure CPV effect Pure matter effect

10. Essential requirements for CPV discovery  Order of magnitude higher statistics from present generation experiments    High intensity beam (Multi-MW)  Increase statistics  High sensitivity huge detector  Increase statistics  Increase signal efficiency  Reduce background  Reduce systematic errors  Should also capable for proton decay detection 10

11. 11 How to measure CPV & sign(  m 23 )  νe appearance energy spectrum shape  Peak position and height for 1st, 2nd maximum and minimum  Measure both sin  & cos  terms  can discriminate 0deg vs 180deg  Difference between νe and νe behavior  Sensitive to any mechanism to make asymmetry (No assumption)  Basically measure sin  term  Distance:  Larger L Matter effect large  Sensitive to sign(  m 23 ) too  Smaller L (lower E): Purer CPV measurement 11 665km2300km CPV Matter

12. Future MW proton facilities in the world 12 Staged approach

13. “Available” technologies for huge detector Liq Ar TPC  Aim O(100kton)  Electronic “bubble chamber”  Can track every charged particle  Down to very low energy  Neutrino energy reconstruction by eg. total energy  No need to assume process type  Capable upto high energy  Good PID w/ dE/dx, pi0 rejection  Realized O(1kton) Water Cherenkov  Aim O(1000kton)  Energy reconstruction assuming Ccqe  Effective < 1GeV  Good PID (  /e) at low energy  Cherenkov threshold  Realized 50kton 13 Good at Wideband beam Good at low E (<1GeV) narrow band beam

14. Possible experimental configuration  Multi-MW beam + Longer distance O(1000km)+ Wide band beam + LiqAr  Energy spectrum measurement  Cover both 1 st and 2 nd peaks  Possible to determine “everything” in 1 shot  CPV  Hierarchy   23 octant  Multi-MW beam + Shorter distance (a few 100km) + Low energy narrow band beam + Water Cherenkov  Nue/nuebar asymtery of 1 st peak  Possible to determine  CPV  Need external input to discriminate mass hierarchy (such as atm nu) 14

15. Planned future CPV experiments Experimental configuration Liq. Ar TPCWCComment MW beam O(1000km) baseline WBB Spectrum measurement J-PARC-Okinoshima (100kt@658km) CERN-Pyhasalmi (LAGUNA, 100kt@2300km) US-LBNE/LAr (34kt@1300km) US-LBNE/WC (200kt@1300km) Sensitive to matter effect = mass hierarchy Could possibly detect deviation from “standard” PMNS spectrum shape MW beam a few 100km baseline Sub-GeV NBB /anti- asymmetry J-PARC-HyperK (540kt@295km) CERN-Frejus (LAGUNA, 440kt@130km) Less dependence on assumption Need other input for mass hierarchy 15

16. P32 proposal (Lar TPC R&D) Recommended by J-PARC PAC (Jan 2010), arXiv:0804.2111 Kamioka L=295km OA=2.5deg Okinoshima L=658km OA=0.78deg Almost On-Axis Scenarios in Japan J-PARC  1.7MW  ??MW

17. J-PARC-HyperK @ Kamioka 3  sin 2  23 =0.6 sin 2  23 =0.5 sin 2  23 =0.4 mass hierarchy determination w/ atmospheric leptonic CPV w/ JPARC 10 yrs exposure of atm. data. Super-K syst. errors are assumed. 5 yrs of 1.66 MW JPARC data. 5% syst. errors are assumed. Very good chance to detect CPV & have potential on sign(  m 23 ) with atm

18. Hyper-K Base-Design 1Mton total volume, twin cavity 0.54Mton fiducial volume Inner (D43m x L250m) x 2 Outer Detector >2m Photo coverage 20% (1/2 x SK) 20” PMT w/ cover FEM analysis (Factor of safety) Base-design to be optimized Geological survey of the site is going on Qualitative studies on physics potential

19. J-PARC to Okinoshima P32 proposal (Lar TPC R&D) Recommended by J-PARC PAC (Jan 2010), arXiv:0804.2111 Scenario 1 19

20. J-PARC to Okinoshima P32 proposal (Lar TPC R&D) Recommended by J-PARC PAC (Jan 2010), arXiv:0804.2111 Scenario 1 20

21. Physics potential Beam ν e Background 21 Very good chance both to detect CPV & determine sign(  m 23 ) CPV Hierarchy

22. European Activities: LAGUNA-LBNO ~500kt Water Cherenkov 100kt Liq Ar. TPC GLACIER

23. LAGUNA-Pyhasalmi sensitivity 23 CPV Mass hierarchy unknown assumption A.Rubbia EPS-HEP 2011

24. R&D toward realizing 100kt LArTPC 24 Site visit Double phase readout test @ ETHZ (CERN RE18) J-PARC T32 exp (ETHZ/KEK/Iwate/Waseda) 250L LAr TPC 180k trig (80k Kaon)

25. LBNE in US 25 B.Svoboda, GLA2011

26. US-LBNE sensitivities 26 T2K region L.Whitehead, B.Rebel @ NNN2010

27. Implication of large  13 on Future  If sin 2 2  13 > ~0.01  Conventional Multi-MW super beam long baseline experiment will be really promising to explore CPV in lepton sector  We need to put even more effort to formulate the future project in this direction as soon as possible  IF not  Need “ideal” beam such as Neutrino Factory or beta beam to probe CPV 27 T2K region

28. Summary  Indication of large  13 makes conventional beam long baseline experiment be promising to probe CPV and sign(  m 23 2 )  To realize the next generation experiment, Multi-MW beam power & High sensitivity huge detector MUST BE REALIZED  Two detector options are under consideration:  O(500kt) Water Cherenkov & 100kton LiqAr TPC  Two promising experimental configurations  WBB w/ LiqAr TPC  Spectrum measurement for 1 st & 2 nd peak  NBB w/ WC  /anti- asymmetry  Design study & R&D for future CPV search are intensively being done around the world  J-PARC  Kamioka (WC)/Okinoshima(LAr)  CERN  Frejus(WC)/Pihasalmi(LAr) (LAGUNA-LBNO)  FNAL  DUSEL (WC/LAr) (LBNE)  It is desirable to realize both configurations in the world, but it may not be so easy  Need to be very careful on physics potential  Personally, I am interested in how to know origin of CPV, whether PMNS or something exotic  International cooperation & coordination needed  EU/Russia/Japan(KEK) are working coherently under LAGUNA consortium  Need to be ready to “go” when finite  13 is concluded 28