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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) NuFact 06 UC Irvine, USA August 24, 2006 Walter Winter Universität Würzburg, Germany
Contents • Introduction • Future experiment types: • Superbeam upgrades • Beta beams • Neutrino factories • Decision making: Which experiment/type? • Summary NuFact 06 - Walter Winter
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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