1. Beyond T2K and NOvA (… and reactor experiments) NuFact 06 UC Irvine, USA August 24, 2006 Walter Winter Universität Würzburg, Germany

2. Aug. 24, 2006NuFact 06 - Walter Winter2 Contents Introduction Introduction Future experiment types: Future experiment types: –Superbeam upgrades –Beta beams –Neutrino factories Decision making: Which experiment/type? Decision making: Which experiment/type? Summary Summary

3. Aug. 24, 2006NuFact 06 - Walter Winter3 Beyond T2K and NOvA: Setting Beyond T2K and NOvA = beyond 2015?! Beyond T2K and NOvA = beyond 2015?! Specific setups less certain than for the coming ten years Specific setups less certain than for the coming ten years  13 discovered if sin 2 2  13 > 0.01  13 discovered if sin 2 2  13 > 0.01 (from: FNAL Proton Driver Study) GLoBES 2005

4. Aug. 24, 2006NuFact 06 - Walter Winter4 After T2K and NOvA: Status  13 discovered, some hint, or no signal at all  13 discovered, some hint, or no signal at all Even if  13 is very large and all data are combined: Even if  13 is very large and all data are combined: –CP violation discovery unlikely –Mass hierarchy discovery 50:50 chance (in deltacp) (see, e.g., NOvA proposal, hep-ex/0503053) (90% CL solid, 3  dashed; from hep-ph/0403068)

5. Aug. 24, 2006NuFact 06 - Walter Winter5 What do we still want to know? Discover  13 (if not yet done) Discover  13 (if not yet done) Establish CP violation (at high CL) Establish CP violation (at high CL) Measure the mass hierarchy (at high CL) Measure the mass hierarchy (at high CL) Measure  13 precisely, say 5% in log 10 (sin 2 2  13 ) Measure  13 precisely, say 5% in log 10 (sin 2 2  13 ) Measure  CP precisely, say 20 degrees Measure  CP precisely, say 20 degrees Measure leading atm. parameters at per cent level Measure leading atm. parameters at per cent level Establish deviation from maximal mixing Establish deviation from maximal mixing Verify MSW effect, constrain non-standard physics, etc. Verify MSW effect, constrain non-standard physics, etc. The only thing from this list which may happen early!

6. Aug. 24, 2006NuFact 06 - Walter Winter6 Options and representatives Major players: NOvA upgrades NOvA upgrades Wide band beam FNAL/BNL to DUSEL Wide band beam FNAL/BNL to DUSEL T2HK/T2KK T2HK/T2KK CERN SPL CERN SPL Superbeam upgrade Beta beam Neutrino factory Performance depends on  :  =100-150: CERN-Frejus?  =100-150: CERN-Frejus?  ~350: Max. at CERN?  ~350: Max. at CERN?  >> 350: “Higher  beam”  >> 350: “Higher  beam”Parameters: Muon energy Muon energy Baseline Baseline Second baseline? Second baseline? Detector performance Detector performance Channels Channels Specific suggestionsWhat to compare that to?Still green-field scenario

7. Superbeam upgrades

8. Aug. 24, 2006NuFact 06 - Walter Winter8 Upgrading NOvA Simplest addition: A second detector, possibly liquid argon Simplest addition: A second detector, possibly liquid argon Main purpose of NOvA:  13, mass hierarchy Main purpose of NOvA:  13, mass hierarchy In principle obtained by matter effects, i.e., long L Originally: Optimization of NOvA-T2K synergy by (Barger, Marfatia, Whisnant, 2002; Huber, Lindner, Winter, 2003; Minakata, Nunokawa, Parke, 2003) In principle obtained by matter effects, i.e., long L Originally: Optimization of NOvA-T2K synergy by (Barger, Marfatia, Whisnant, 2002; Huber, Lindner, Winter, 2003; Minakata, Nunokawa, Parke, 2003) Two possibilities for upgrades: Two possibilities for upgrades: –Detector at same L/E but different L, i.e., matter effect (similar to above) (Mena, Palomarez-Ruiz, Pascoli, 2005a/b) –Detector at 2 nd osc. Maximum (possibly at shorter L) (NOvA proposal, hep-ex/0503053) See also WG 1: Howcroft

9. Aug. 24, 2006NuFact 06 - Walter Winter9 NOvA+2 nd detector Same L/E: Bi-probability ellipses shrink to lines Same L/E: Bi-probability ellipses shrink to lines MH discovery for all  CP for sin 2 2  13 > 0.04 MH discovery for all  CP for sin 2 2  13 > 0.04 More efficient than 2 nd osc. maximum for running only More efficient than 2 nd osc. maximum for running only (Mena, Palomarez-Ruiz, Pascoli, 2005a/b) Thin: 2 nd osc. max Thick: Same L/E (2 x 50kt liquid argon, no PD) 5 yr 5 yr  5 yr anti- 2.4 o OA

10. Aug. 24, 2006NuFact 06 - Walter Winter10 Broad band beam (1) Idea: Use on-axis beam for the simul- taneous measurement of different oscillation maxima Idea: Use on-axis beam for the simul- taneous measurement of different oscillation maxima Probably FNAL or BNL to DUSEL (=Homestake/Henderson/…) from FNAL: 1290/1487 km, from BNL: 2540/2770 km Probably FNAL or BNL to DUSEL (=Homestake/Henderson/…) from FNAL: 1290/1487 km, from BNL: 2540/2770 km Challenge: Backgrounds in a WC detector Challenge: Backgrounds in a WC detector Compared to NOvA upgrades: New beamline required; therefore: Different timescale? Compared to NOvA upgrades: New beamline required; therefore: Different timescale? (Diwan et al, hep-ph/0303081; Diwan, hep-ex/0407047) See also WG 1: Bishai

11. Aug. 24, 2006NuFact 06 - Walter Winter11 Broad band beam (2) Baseline does not really matter so much Baseline does not really matter so much Absolute performance very competitive Absolute performance very competitive (New study using GLoBES: Barger et al, hep-ph/0607177) 1 MW, 5 yr  + + 2 MW 5yr anti-, 300 kt WC detector; 3  FNAL BNL Worst case  CP Best case  CP “Typical”  CP Best case  CP CP frac. 0.75

12. Aug. 24, 2006NuFact 06 - Walter Winter12 T2K upgrades: T2HK, T2KK T2HK: Upgrade of T2K to megaton-size detector + 4 MW beam power T2HK: Upgrade of T2K to megaton-size detector + 4 MW beam power T2KK: Split detector mass into two identical detectors in Japan+ Korea (0.27+0.27 Mt) at same OA: T2KK: Split detector mass into two identical detectors in Japan+ Korea (0.27+0.27 Mt) at same OA: –Larger matter effects (L=1050 km) –Reduce systematics impact (T2HK: Itow et al, hep-ex/0106019; T2KK: Ishitsuka, Kajita, Minakata, Nunokawa, 2005) See also WG 1: Okamura

13. Aug. 24, 2006NuFact 06 - Walter Winter13 What does the 1050 km baseline help? What does the 1050 km baseline help? What does it help that the detectors are identical? What does it help that the detectors are identical? T2KK: Key questions (Barger, Huber, Marfatia, Winter, in preparation) “Correlated errors” between detectors, but uncorrelated between neutrino-antineutrino channels! (3  m 31 2 =0.0025 eV 2  PRELIMINARY

14. Aug. 24, 2006NuFact 06 - Walter Winter14 CERN-Memphys (a superbeam-beta beam hybrid) Beta beam (  =100) plus 4MW superbeam to 440 kt WC detector at Frejus site (L=130 km) Beta beam (  =100) plus 4MW superbeam to 440 kt WC detector at Frejus site (L=130 km) Effect of systematics smaller and absolute performance better than for T2HK Effect of systematics smaller and absolute performance better than for T2HK Antineutrino running not necessary because e to  (beta beam) and  to e (superbeam) channels present Antineutrino running not necessary because e to  (beta beam) and  to e (superbeam) channels present (Campagne, Maltoni, Mezzetto, Schwetz, 2006) 10 years, 3  Shading: systematics varied from 2% to 5% Example:  13 discovery

15. Aug. 24, 2006NuFact 06 - Walter Winter15 Beta beam Key figure (any beta beam): Useful ion decays/year? Key figure (any beta beam): Useful ion decays/year? “Standard values”: 3 10 18 6 He decays/year 1 10 18 18 Ne decays/year “Standard values”: 3 10 18 6 He decays/year 1 10 18 18 Ne decays/year  Can these be achieved? Typical gamma ~ 100 – 150 (for CERN SPS) Typical gamma ~ 100 – 150 (for CERN SPS) (CERN layout; Bouchez, Lindroos, Mezzetto, 2003; Lindroos, 2003; Mezzetto, 2003; Autin et al, 2003) Compared to superbeam: no intrinsic beam BG limiting the sin 2 2  13 sensitivity to > 10 -3 Compared to superbeam: no intrinsic beam BG limiting the sin 2 2  13 sensitivity to > 10 -3 Compared to neutrino factory: no charge identification required, operation at the oscillation maximum possible/reasonable Compared to neutrino factory: no charge identification required, operation at the oscillation maximum possible/reasonable  What is the physics case for a beta beam between SB and NF? (Zucchelli, 2002) SEE ALSO NEXT TALK

16. Aug. 24, 2006NuFact 06 - Walter Winter16 From low to very high gamma “Low” gamma (  <150?) “Low” gamma (  <150?) -Alternative to superbeam/synergy with superbeam? -Originally designed for CERN (SPS) -Water Cherenkov detector (see before; also: Volpe, 2003; Campagne, Maltoni, Mezzetto, Schwetz, 2006) “Medium” gamma (150<  <350?) “Medium” gamma (150<  <350?) -Alternative to superbeam! -Possible at upgraded SPS? -Water Cherenkov detector (Burguet-Castell et al, 2004+2005; Huber et al, 2005) “High” gamma (  >> 350?) “High” gamma (  >> 350?) -Alternative to neutrino factory? -Requires large accelerator -Detector technology other than water? (Burguet-Castell et al, 2004; Huber et al, 2005; Agarwalla et al, 2005) (Fig. from Huber, Lindner, Rolinec, Winter, 2005) (for NOvA-like detector!) Gamma determines neutrino energy and therefore detector technology! See also WG 1: Mezzetto, Fernandez-Martinez, Couce

17. Aug. 24, 2006NuFact 06 - Walter Winter17 Beta beam vs. Superbeam vs. NuFact? Low/medium  : Can easily compete with superbeam upgrades Low/medium  : Can easily compete with superbeam upgrades Higher  : At least theoretically competitive to a neutrino factory Higher  : At least theoretically competitive to a neutrino factory Challenges: Challenges: -Can fluxes be reached? -Compare completely optimized accelerator strategies? -Mass hierarchy measurement for small  13 (Fig. from Huber, Lindner, Rolinec, Winter, 2005)

18. Aug. 24, 2006NuFact 06 - Walter Winter18 Neutrino factory Ultimate “high precision” instrument!? Ultimate “high precision” instrument!? Muon decays in straight sections of storage ring Muon decays in straight sections of storage ring Technical challenges: Target power, muon cooling, charge identification, maybe steep decay tunnels Technical challenges: Target power, muon cooling, charge identification, maybe steep decay tunnels (from: CERN Yellow Report ) p Target , K  Decays  -Accelerator  Cooling “Right sign” “Wrong sign” “Right sign” “Wrong sign” (Geer, 1997; de Rujula, Gavela, Hernandez, 1998; Cervera et al, 2000) SEE ALSO ISS TALKS

19. Aug. 24, 2006NuFact 06 - Walter Winter19 Which baseline(s), which energy? 3000-5000 km good for CP violation 3000-5000 km good for CP violation 7500 km good for MH, as degeneracy resolver 7500 km good for MH, as degeneracy resolver Use two baselines: 4000 km+7500 km, E  > 40 GeV Use two baselines: 4000 km+7500 km, E  > 40 GeV Mass hier. CP violation  13 sens. Fig. from Huber, Lindner, Rolinec, Winter, hep-ph/0606119. See also: Barger, Geer, Whisnant, 1999; Cervera et al, 2000; Burguet-Castell et al, 2001; Freund, Huber, Lindner, 2001

20. Aug. 24, 2006NuFact 06 - Walter Winter20 Why else want a very long baseline? L ~ 6000-9000 km Example:  13 precision Example:  13 precision Depends on (true)  CP (green band); thick curve: “typical”  CP (median) Depends on (true)  CP (green band); thick curve: “typical”  CP (median) L ~ 7500 km as risk- minimizer, and for better absolute performance L ~ 7500 km as risk- minimizer, and for better absolute performance In comb. with short baseline (L=4000 km) less sensitive to L In comb. with short baseline (L=4000 km) less sensitive to L (Gandhi, Winter, in preparation)

21. Aug. 24, 2006NuFact 06 - Walter Winter21 More R&D: Detector optimization? Improved detector would increase sensitivity reach significantly Improved detector would increase sensitivity reach significantly In addition: Lower E  = 20 GeV possible (while 50 GeV do not harm) In addition: Lower E  = 20 GeV possible (while 50 GeV do not harm) Improve energy resolution ? Improve energy resolution ? Lower appearance threshold (CID!) to 1 GeV + use more realistic BG model Lower appearance threshold (CID!) to 1 GeV + use more realistic BG model Thick gray curve: Optimization potential (Huber, Lindner, Rolinec, Winter, hep-ph/0606119) See also WG 1: Cervera, Rubbia

22. Aug. 24, 2006NuFact 06 - Walter Winter22 Additional channels: Silver, Platinum Silver ( e to  ): Silver ( e to  ): –Standard: 5kt ECC (Autiero et al, 2004) –Optimistic: 10kt ECC, 5xSIG, 3xBG Platinum (  to e ): Platinum (  to e ): –Standard: 15 kt, 20% efficiency, ~ 7.5 GeV upper threshold (Rubbia, 2001) –Optimistic: 50 kt, 40% efficiency, E  upper threshold –Optimistic: 50 kt, 40% efficiency, E  upper threshold Large  13 : Platinum useful? Large  13 : Platinum useful? Medium  13 : Both useful? But: Other choices in this range! However: Unitarity tests? (Antusch et al, 2006) Medium  13 : Both useful? But: Other choices in this range! However: Unitarity tests? (Antusch et al, 2006) (Huber, Lindner, Rolinec, Winter, hep-ph/0606119)

23. Aug. 24, 2006NuFact 06 - Walter Winter23 NF optimization potential Optimized NuFact: Excellent  13 reach for both MH and CPV Optimized NuFact: Excellent  13 reach for both MH and CPV But: For sin 2 2  13 ~ 10 -2,  =350 beta beam (L=730 km) better But: For sin 2 2  13 ~ 10 -2,  =350 beta beam (L=730 km) better 33 (Huber, Lindner, Rolinec, Winter, hep-ph/0606119;  -beam: Burguet-Castell et al, hep-ph/0503021 )

24. Aug. 24, 2006NuFact 06 - Walter Winter24 Decision making: Simplified Do we have enough information to make a decision after T2K and NOvA? Do we have enough information to make a decision after T2K and NOvA? Assumptions for this talk: Assumptions for this talk: –We have to make a decision based on this information –There will be no further incremental approach to search for   (if not found) = “One more experiment” hypothesis –We use the option with the lowest effort if two physically similar Key questions: Key questions: –Superbeam upgrade, beta beam, or neutrino factory? –What setup within each class has the best physics performance? One more experiment?

25. Aug. 24, 2006NuFact 06 - Walter Winter25 Decision making: Physics cases Possible outcomes after T2K and NOvA Possible outcomes after T2K and NOvA 1.  13 discovered 2. Few  hint for  13 3.  13 not found A possible future strategy based on that (biased): A possible future strategy based on that (biased): 1.Best possible setup for large  13 with reasonable effort = Superbeam upgrade? But which? Strategy: Max. CP fraction for discoveries for sin 2 2  13 > 0.04? 2.Best possible setup for intermediate  13 = Beta beam with  ~350? Other with better MH reach/longer L? Strategy: Max. CP fraction for discoveries for sin 2 2  13 ~ 0.01 3.Best possible reach in  13 for all performance indicators = Neutrino factory Strategy: Disoveries for  13 as small as possible

26. Aug. 24, 2006NuFact 06 - Walter Winter26 Decision making: Example Blue: Superbeam upgrade based upon: lower effort Blue: Superbeam upgrade based upon: lower effort Green: Beta beam based upon: Good CPV reach, MH in most cases Green: Beta beam based upon: Good CPV reach, MH in most cases Red: Neutrino factory (optimized) based upon: Good  13 reach Red: Neutrino factory (optimized) based upon: Good  13 reach (3  m 31 2 =0.0022 eV 2  Longer L

27. Aug. 24, 2006NuFact 06 - Walter Winter27 Which option for large  13 ? (from Huber et al, hep-ph/0601266) Based on assumptions before (lowest possible effort): Superbeam? Based on assumptions before (lowest possible effort): Superbeam? Depends on systematics: Requires more R&D Depends on systematics: Requires more R&D Important selection criterion: Systematics robustness? Important selection criterion: Systematics robustness? Depends on what optimized for: MH or CPV Therefore: take two? Depends on what optimized for: MH or CPV Therefore: take two?

28. Aug. 24, 2006NuFact 06 - Walter Winter28 Summary What is (more or less) known: What is (more or less) known: –Neutrino factory best alternative for small  13 to measure both MH and CPV; a very long baseline is an essential component of that –For large  13, a different alternative may be better –There may be a separate physics case for a beta beam What is not known: What is not known: –Which setup for large  13 ? Possibly two, such as T2HK (for CPV) + WBB (MH)? Which has the lowest systematics impact? T2KK? –What is the precise physics case for a beta beam? How does that affect the choice of  and L? –How far can a neutrino factory be optimized?