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Long baseline neutrino oscillations: Theoretical aspects

Long baseline neutrino oscillations: Theoretical aspects. NOW 2008 Conca Specchiulla, Italy September 9, 2008 Walter Winter Universität Würzburg. TexPoint fonts used in EMF: A A A A A A A A. Contents. Theoretical motivation: Quantities of interest How to measure these? - Phenomenology

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Long baseline neutrino oscillations: Theoretical aspects

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  1. Long baseline neutrino oscillations:Theoretical aspects NOW 2008 Conca Specchiulla, Italy September 9, 2008Walter Winter Universität Würzburg TexPoint fonts used in EMF: AAAAAAAA

  2. Contents • Theoretical motivation:Quantities of interest • How to measure these? - Phenomenology • Experiment choice and optimization • Neutrino factory: what can we expect? • The potentially unexpected • Summary

  3. Quantities of interest

  4. Theoretical motivation • Mass models describe masses and mixings (mass matrices) by symmetries, GUTs, anarchy arguments, etc. • From that: predictions for observables • Example: Literature research for q13 • q13 as performance indicator for models (Albright, Chen, 2006) Talk: Mu-Chun Chen, Friday

  5. Some other examples • Large mixingsfrom CL and n sectors?Example: q23l = q12n = p/4, perturbations from CL sector(can be connected with textures)(Niehage, Winter, 2008) • Another example: QLC+Flavor symmetrieslead e.g. to Modern QLC scenarios do not have an exact factor k=1 there (depends on model)(e.g. Plentinger, Seidl, Winter, 2008; see also: Frampton, Matsuzaki, 2008) dCPandoctantdiscriminatethese examples! k as performance indicator for QLC models k

  6. Perform. indicators for theoryWhat observables test the theory space most efficiently? • Magnitude of q13 (see before!) • Mass hierarchy(strongly affects textures) • Deviations from max. mixing(nm-nt symmetry?) • q23 octant • |sin2q12-1/3|(tribimaximal mixings?) • |sindCP-1| (CP violation)(leptogenesis?) • Value of dCP • k qC+ q12 ~ p/4 ~ q23(k as indicator for quark-lepton unification models?) • Dev. from std. osc. framework (Antusch et al, hep-ph/0404268) Most important for LBL experiments

  7. Long baseline phenomenology

  8. Why GeV energies? Unoscillated flux • Cross sections ~ E (DIS regime) • Flux ~ E2 (beam collimation) • For fixed L: unoscillated event rate ~ E3 Oscillated flux • Adjust baseline to stay on osc. maximumFlux ~ 1/L2, L ~ E on oscillation maximum • Event rate ~ E on oscillation maximum • In addition:Matter effects (resonance energy ~ 10 GeV in Earth‘s mantle) • Measure mass hierarchy, Flux(L) ~ const. at resonance

  9. GeV Long baseline experiments For leading atm. params Signal prop. sin22q13 Contamination

  10. Channels of interest • Disappearance for Dm312, q23: nm nmNB: We expand in • Appearance for q13, CPV, MH: • Golden: ne nm (NF/BB) or nm ne(SB)(e.g., De Rujula, Gavela, Hernandez, 1999; Cervera et al, 2000) • Silver: ne nt (NF – low statistics!?)(Donini, Meloni, Migliozzi, 2002; Autiero et al, 2004) • Platinum: nm ne (NF: difficult!)(see e.g. ISS physics working group report) • Other appearance: nm nt (OPERA, NF?) • Neutral currents for new physics (e.g., Barger, Geer, Whisnant, 2004; MINOS, 2008) D31 = Dm312 L/(4E)

  11. Appearance channels • Antineutrinos: • Magic baseline: • Silver: • Superbeams, Plat.: (Cervera et al. 2000; Freund, Huber, Lindner, 2000; Huber, Winter, 2003; Akhmedov et al, 2004)

  12. Degeneracies Iso-probability curves • CP asymmetry(vacuum) suggests the use of neutrinos and antineutrinos • One discrete deg.remains in (q13,d)-plane(Burguet-Castell et al, 2001) • Additional degeneracies: (Barger, Marfatia, Whisnant, 2001) • Sign-degeneracy (Minakata, Nunokawa, 2001) • Octant degeneracy (Fogli, Lisi, 1996) b-beam, n b-beam, anti-n Best-fit

  13. Degeneracy resolution WBB FNAL-DUSEL, T2KK, NF@long L, … Monochromatic beam, Beta beam with different isotopes, WBB, … T2KK, magic baseline ~ 7500 km, SuperNOvA Neutrino factory, beta beam, Mton WC SB+BB CERN-Frejus, silver/platinum @ NF Atmospheric, … • Matter effects (sign-degeneracy) – long baseline, high E • Different beam energies or better energy resolution in detector • Second baseline • Good enough statistics • Other channels • Other experimentclasses Talk: Thomas Schwetz (Minakata, Nunokawa, 2001; Parke) (many many authors, see e.g. ISS physics WG report)

  14. On-axis WBB versus off-axis NBBExample: NuMI-like beam  100kt liquid argon On axis sin22q13 CP violation Mass hierarchy FNAL-DUSELWBB dCP=-p/2 Ash RiverOA,NOvA* ConstraintfromNuMIbeam dCP=+p/2 C (Barger et al, hep-ph/0703029) Off-axis technology may not be necessary if the detector is good enough, i.e., has good BG rejection and good energy resolution! WC good enough???

  15. Quantification of performance Commonly used performance indicators:

  16. Example: Discovery reaches… and the “Fraction of dCP” Sometimes:choose specifc dCP, e.g. 3p/2(worst/best case) Sensitive region as function of trueq13 anddCP C dCP values now stacked for each q13 A Simplifications: Sometimes: Band for risk wrt dCP Worst case q13 reach Read: If sin22q13=0.04, we expect a discovery for 20% of all values of dCP E D “Typical” dCP:CP fraction 50% F B Best case q13reach G

  17. Experiment choice and optimization (some thoughts)

  18. Optimization of exps • Small q13:Optimize q13, MH, and CPV discovery reaches in q13 direction • Large q13:Optimize q13, MH, and CPV discovery reaches in (true) dCPdirection • What defines “large q13”? A Double Chooz, Day Bay, T2K, … discovery? When? Beta beam B Optimization for large q13 NuFact T2KK Optimization for small q13 (3s, Dm312=0.0022 eV2)

  19. Timescale for q13 discovery? • Assume:Decision on future experiments made after some LHC running and next-generation experiments • Two examples: • ~ 2011: sin22q13 > 0.04? • ~ 2015: sin22q13 > 0.01? D (Huber, Kopp, Lindner, Rolinec, Winter, 2006)

  20. Large q13 strategy • Assume that Double Chooz finds q13 • Minimum wish listeasy to define: • 5s independent confirmation of q13 > 0 • 3s mass hierarchy determination for any (true) dCP • 3s CP violation determination for 80% (true) dCP For any (true) q13 in 90% CL D-Chooz allowed range! • What is the minimal effort (minimal cost) for that? • NB: Such a minimum wish list is non-trivial for small q13 • NB: CP fraction 80% comes from comparison with IDS-NF baseline etc. (arXiv:0804.4000; Sim. from hep-ph/0601266; 1.5 yr far det. + 1.5 yr both det.)

  21. Example: Minimal beta beam (arXiv:0804.4000) • Minimal effort = • One baseline only • Minimal g • Minimal luminosity • Any L (green-field!) • Example: Optimize L-g for fixed Lumi: • g as large as 350 may not even be necessary! Sensitivity for entire Double Chooz allowed range! More on beta beams: Mezzetto‘s talk! 5yr x 1.1 1018 Ne and 5yr x 2.9 1018 He useful decays

  22. Small q13 strategy • Assume that Double Chooz … do not find q13 • Minimum wish list: • 3s-5s discovery of q13 > 0 • 3s mass hierarchy determination • 3s CP violation determination For as small as possible (true) q13 • Two unknowns here: • For what fraction of (true) dCP? One has to make a choice (e.g. max. CP violation, for 80% of all dCP, for 50%, …) • How small q13 is actually good enough? • Minimal effort is a matter of cost! • Maybe the physics case will be defined otherwise?

  23. Connection to high-E frontier?

  24. Optimal strategy vs. regional interests? So far: purely conceptual … … however, the optimal strategy depends on regional boundary conditions! Talks:Goodman (US)Evans (MINOS)Kurimoto (SciBooNE) Talks:Ronga (Gran Sasso)Scott-Lavina (OPERA)Sala (CNGS) Talks:Kakuno (T2K)Dufour (T2KK) CERN-INO?JHF-INO?Talk: Goswami

  25. Physics potential of the neutrino factory: what can we expect?

  26. International design study (Geer, 1997; de Rujula, Gavela, Hernandez, 1998; Cervera et al, 2000) IDS-NF: • Initiative from ~ 2007-2012 to present a design report, schedule, cost estimate, risk assessment for a neutrino factory • In Europe: Close connection to „Euronus“ proposal within the FP 07 • In the US: „Muon collider task force“ Signal prop. sin22q13 Contamination Muons decay in straight sections of a storage ring ISS Talks:Long (IDS-NF)Bonesini (R&D)

  27. IDS-NF baseline setup 1.0 • Two decay rings • Em=25 GeV • 5x1020 useful muon decays per baseline(both polarities!) • Two baselines:~4000 + 7500 km • Two MIND, 50kt each • Currently: MECC at shorter baseline (https://www.ids-nf.org/) More by Ken Long

  28. Physics potential 3s • Excellent q13, MH, CPV discovery reaches B B B (IDS-NF, 2007) • About 10% full width error (3s) on log10 (sin22q13) for sin22q13 = 0.001(Gandhi, Winter, hep-ph/0612158, Fig. 6) • About 20-60 degree full width error (3s) on dCP for sin22q13 = 0.001 (Huber, Lindner, Winter, hep-ph/0412199, Fig. 7)But what does that mean? Cabibbo angle-precision (qC ~ 13 deg.)!Why is that relevant? Can be another feature of nontrivial QLC models:E.g. from specific texture+QLC-type assumptions:(F: model parameter) (Niehage, Winter, 2008)

  29. Two-baseline optim. revisited • Robust optimum for ~ 4000 + 7500 km • Optimization even robust under non-standard physics(dashed curves) C C (Kopp, Ota, Winter, 2008)

  30. Matter density measurement • Assume that only one parameter measured:Constant referencedensity rRefor lower mantle density rLM True d=0 (Minakata, Uchinami, 2007; Gandhi, Winter, 2007)

  31. MSW effect in Earth matter • Solar term:Note thati.e., effect (initially) increases with baseline (D ~ L)!MSW effect sensitivity evenfor q13=0! 5s C (hep-ph/0411309)

  32. Octant degeneracy (Gandhi, Winter, 2007) • 4000 km alone: Problems with degs for intermediate q13 • 7200 km alone: No sensitivity for small q13 • 4000 km + 7200 km: Good for all q13 Similar performanceto Gold+Silver* @ 4000kmMeloni, arXiv:0802.0086

  33. The unexpected!?

  34. Neutrino osc. framework incomplete? See also talk by D. Meloni • Example: non-standard interactions (NSI) from effective four-fermion interactions: • Discovery potential for NSI-CP violation in neutrino propagation at the NFEven if there is no CPV instandard oscillations, we mayfind CPV!But what are the requirements for a model to predict such large NSI? ~ current bound (arXiv:0808.3583) 3s  Talk by T. Ota

  35. Help from other experiments? • Physics scenario:Double Chooz finds q13and ~ a total of 100 muon tracks from astrophysical sources observed (ratio of muon tracks to showers),only m1 stableon extragalatic distances • Double Choozalone and this informationcould establish CPV • Other sources of information: Supernovae, atmospheric, LHC, 0nbb, ... (Maltoni, Winter, 2008) Talks: Petcov, Schwetz, Sigl, …

  36. Outlook: How to design the optimal experiment Physics Theory Performance indicators: q13, CP violation, MH, … Correlations+Degeneracies Resolution strategies New physics? Inclusive strategies(more channels, etc.) Future LBL experiment Same measurementby other experiment(e.g., MH from supernova) Potitical boundary conditions(e.g., Obama vs. McCain) Regionalinterests(e.g., DUSEL, T2KK, …) LHC(e.g.,connection to high-E frontier) Politics

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