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Beyond T2K and NOvA (… and reactor experiments)

Beyond T2K and NOvA (… and reactor experiments). NuFact 06 UC Irvine, USA August 24, 2006 Walter Winter Universit ät Würzburg, Germany. Contents. Introduction Future experiment types: Superbeam upgrades Beta beams Neutrino factories Decision making: Which experiment/type? Summary.

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Beyond T2K and NOvA (… and reactor experiments)

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

  2. Contents • Introduction • Future experiment types: • Superbeam upgrades • Beta beams • Neutrino factories • Decision making: Which experiment/type? • Summary NuFact 06 - Walter Winter

  3. Beyond T2K and NOvA: Setting • Beyond T2K andNOvA = beyond 2015?! • Specific setups less certain than for the coming ten years • q13 discovered if sin22q13 > 0.01 GLoBES 2005 (from: FNAL Proton Driver Study) NuFact 06 - Walter Winter

  4. After T2K and NOvA: Status • q13 discovered, some hint, or no signal at all • Even if q13 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, 3s dashed; from hep-ph/0403068) NuFact 06 - Walter Winter

  5. What do we still want to know? The only thing from this list which may happen early! • Discover q13 (if not yet done) • Establish CP violation (at high CL) • Measure the mass hierarchy (at high CL) • Measure q13 precisely, say 5% in log10(sin22q13) • Measure dCP precisely, say 20 degrees • Measure leading atm. parameters at per cent level • Establish deviation from maximal mixing • Verify MSW effect, constrain non-standard physics, etc. NuFact 06 - Walter Winter

  6. Options and representatives Superbeamupgrade Beta beam Neutrinofactory Major players: • NOvA upgrades • Wide band beamFNAL/BNL to DUSEL • T2HK/T2KK • CERN SPL Performance depends on g: • g=100-150:CERN-Frejus? • g~350:Max. at CERN? • g >> 350:“Higher g beam” Parameters: • Muon energy • Baseline • Second baseline? • Detector performance • Channels Specific suggestions What to compare that to? Still green-field scenario NuFact 06 - Walter Winter

  7. Superbeam upgrades

  8. Upgrading NOvA See also WG 1:Howcroft • Simplest addition: A second detector, possibly liquid argon • Main purpose of NOvA: q13, mass hierarchy • In principle obtained by matter effects, i.e., long LOriginally: Optimization of NOvA-T2K synergy by(Barger, Marfatia, Whisnant, 2002; Huber, Lindner, Winter, 2003; Minakata, Nunokawa, Parke, 2003) • 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 2nd osc. Maximum (possibly at shorter L)(NOvA proposal, hep-ex/0503053) NuFact 06 - Walter Winter

  9. NOvA+2nd detector (Mena, Palomarez-Ruiz, Pascoli, 2005a/b) • Same L/E: Bi-probability ellipses shrink to lines • MH discovery for all dCP for sin22q13 > 0.04 • More efficient than 2nd osc. maximum for n running only 5 yr n 2.4o OA 5 yr n+5 yr anti-n Thin: 2nd osc. maxThick: Same L/E(2 x 50kt liquid argon, no PD) NuFact 06 - Walter Winter

  10. See also WG 1:Bishai Broad band beam (1) (Diwan et al, hep-ph/0303081; Diwan, hep-ex/0407047) • 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 • Challenge: Backgrounds in a WC detector • Compared to NOvA upgrades: New beamline required; therefore: Different timescale? NuFact 06 - Walter Winter

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

  12. T2K upgrades: T2HK, T2KK (T2HK: Itow et al, hep-ex/0106019; T2KK: Ishitsuka, Kajita, Minakata, Nunokawa, 2005) • 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: • Larger matter effects (L=1050 km) • Reduce systematics impact See also WG 1:Okamura NuFact 06 - Walter Winter

  13. T2KK: Key questions • What does the 1050 km baseline help? • What does it help that the detectors are identical? PRELIMINARY “Correlated errors” between detectors,but uncorrelated between neutrino-antineutrino channels! (3s, Dm312=0.0025 eV2) (Barger, Huber, Marfatia, Winter, in preparation) NuFact 06 - Walter Winter

  14. CERN-Memphys(a superbeam-beta beam hybrid) Example: q13 discovery • Beta beam (g=100) plus4MW superbeam to 440 ktWC detector at Frejus site (L=130 km) • Effect of systematics smaller and absolute performance better than for T2HK • Antineutrino running not necessary because ne to nm(beta beam) and nm to ne(superbeam) channels present 10 years, 3sShading: systematics varied from 2% to 5% (Campagne, Maltoni, Mezzetto, Schwetz, 2006) NuFact 06 - Walter Winter

  15. Beta beam SEE ALSO NEXT TALK • Compared to superbeam: no intrinsic beam BG limiting the sin22q13 sensitivity to > 10-3 • 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? • Key figure (any beta beam):Useful ion decays/year? • “Standard values”:3 10186He decays/year1 101818Ne decays/year • Can these be achieved? • Typical gamma ~ 100 – 150 (for CERN SPS) (Zucchelli, 2002) (CERN layout; Bouchez, Lindroos, Mezzetto, 2003; Lindroos, 2003; Mezzetto, 2003; Autin et al, 2003) NuFact 06 - Walter Winter

  16. From low to very high gamma Gamma determines neutrino energyand therefore detector technology! • “Low” gamma (g<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<g<350?) • Alternative to superbeam! • Possible at upgraded SPS? • Water Cherenkov detector (Burguet-Castell et al, 2004+2005; Huber et al, 2005) • “High” gamma (g >> 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!) See also WG 1:Mezzetto, Fernandez-Martinez, Couce NuFact 06 - Walter Winter

  17. Beta beam vs. Superbeam vs. NuFact? • Low/medium g:Can easily compete with superbeam upgrades • Higher g:At least theoretically competitive to a neutrino factory • Challenges: • Can fluxes be reached? • Compare completely optimized accelerator strategies? • Mass hierarchy measurement for small q13 (Fig. from Huber, Lindner, Rolinec, Winter, 2005) NuFact 06 - Walter Winter

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

  19. Which baseline(s), which energy? • 3000-5000 km good forCP violation • 7500 km good for MH, asdegeneracy resolver • Use two baselines: 4000 km+7500 km, Em > 40 GeV CP violation q13 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 Mass hier. NuFact 06 - Walter Winter

  20. Why else want a very long baseline?L ~ 6000-9000 km • Example: q13 precision • Depends on (true) dCP (green band); thick curve: “typical” dCP (median) • L ~ 7500 km as risk-minimizer, and for better absolute performance • In comb. with short baseline (L=4000 km) less sensitive to L (Gandhi, Winter, in preparation) NuFact 06 - Walter Winter

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

  22. Additional channels: Silver, Platinum • Silver (ne to nt): • Standard: 5kt ECC(Autiero et al, 2004) • Optimistic: 10kt ECC, 5xSIG, 3xBG • Platinum (nm to ne): • Standard: 15 kt, 20% efficiency, ~ 7.5 GeV upper threshold(Rubbia, 2001) • Optimistic: 50 kt, 40% efficiency, Em upper threshold • Large q13: Platinum useful? • Medium q13: Both useful?But: Other choices in this range!However: Unitarity tests? (Antusch et al, 2006) (Huber, Lindner, Rolinec, Winter, hep-ph/0606119) NuFact 06 - Walter Winter

  23. NF optimization potential (Huber, Lindner, Rolinec, Winter, hep-ph/0606119; b-beam: Burguet-Castell et al, hep-ph/0503021) • Optimized NuFact: Excellent q13 reach for both MH and CPV • But: For sin22q13 ~ 10-2, g=350 beta beam (L=730 km) better 3s NuFact 06 - Walter Winter

  24. Decision making: Simplified • Do we have enough information to make a decision after T2K and NOvA? • Assumptions for this talk: • We have to make a decision based on this information • There will be no further incremental approach to search for q13 (if not found)= “One more experiment” hypothesis • We use the option with the lowest effort if two physically similar • Key questions: • Superbeam upgrade, beta beam, or neutrino factory? • What setup within each class has the best physics performance? One moreexperiment? NuFact 06 - Walter Winter

  25. Decision making: Physics cases • Possible outcomes after T2K and NOvA • q13 discovered • Few s hint for q13 • q13 not found • A possible future strategy based on that (biased): • Best possible setup for large q13with reasonable effort = Superbeam upgrade? But which?Strategy: Max. CP fraction for discoveries for sin22q13 > 0.04? • Best possible setup for intermediate q13 =Beta beam with g~350? Other with better MH reach/longer L?Strategy: Max. CP fraction for discoveries for sin22q13 ~ 0.01 • Best possible reach in q13 for all performance indicators =Neutrino factoryStrategy: Disoveries for q13 as small as possible NuFact 06 - Walter Winter

  26. Decision making: Example • Blue: Superbeam upgrade based upon: lower effort • Green: Beta beam based upon: Good CPV reach, MH in most cases • Red: Neutrino factory (optimized) based upon: Good q13 reach Longer L (3s, Dm312=0.0022 eV2) NuFact 06 - Walter Winter

  27. Which option for large q13? (from Huber et al, hep-ph/0601266) • Based on assumptions before (lowest possible effort): Superbeam? • Depends on systematics:Requires more R&D • Important selection criterion: Systematics robustness? • Depends on what optimized for: MH or CPVTherefore: take two? NuFact 06 - Walter Winter

  28. Summary • What is (more or less) known: • Neutrino factory best alternative for small q13 to measure both MH and CPV;a very long baseline is an essential component of that • For large q13, a different alternative may be better • There may be a separate physics case for a beta beam • What is not known: • Which setup for large q13? 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 g and L? • How far can a neutrino factory be optimized? NuFact 06 - Walter Winter

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