Neutrino oscillations: Perspective of long-baseline experiments 522. Wilhelm and Else Heraeus-Seminar: Exploring the neutrino sky and fundamental particle physics on the Megaton scale Bad Honnef, Jan. 21, 2013 Walter Winter Universität Würzburg TexPoint fonts used in EMF: AAAAA A A A

2 Contents  Introduction  Measurement of  CP : Experiments and phenomenology  The critical issue for large  13 : Systematics?  Long-baseline alternatives with new technologies?  Comment on sterile neutrinos  Summary

3 (also: T2K, Double Chooz, RENO) (short baseline)

4 Consequences of large  13   13 to be well measured by Daya Bay  Mass hierarchy: 3  discovery for up to 40% of all  CP possible iff ProjectX, possibly until 2025  CP violation measurement extremely difficult Need new facility! Huber, Lindner, Schwetz, Winter, 2009

5 Mass hierarchy measurement?  Mass hierarchy discovery possible with atmospheric neutrinos? (liquid argon, HyperK, MEMPHYS, INO, PINGU, ORCA …) Barger et al, arXiv: ; IH more challenging  NB: basically any new LBL experiment at design luminosity with E > 1 GeV and L >> 600 km can for all  CP measure the hierarchy in e -  transition (MSW effect)!  Alternative: medium-baseline reactor experiments, perhaps Perhaps different facilities for MH and CPV proposed/discussed?  Talks by Smirnov (2), Resconi, Heijboer

Measurement of  CP : Experiments and phenomenology

7 Why is  CP interesting?  CP violation Necessary condition for successful baryogenesis (dynamical mechanism to create matter-antimatter asymmetry of the universe)  thermal leptogenesis by decay of heavy see-saw partner?  Model building e.g. TBM sum rule:  12 = 35  +  13 cos  (Antusch, King; Masina)  Need performance which is equally good for all  CP Symmetry e.g. TBM, BM, …? Correction leading to non-zero  13 ? sin  cos 

8  Antineutrinos: Problem: Earth matter violates CP, CPT explicitely!  Silver: Challenging (  threshold, many  decay channels, vertex res.)  Platinum, T-inv.: Works only for Superbeam + Beta beam (later) Long-baseline oscillations (Cervera et al. 2000; Freund, Huber, Lindner, 2000; Akhmedov et al, 2004) Large!

9 There are three possibilities to artificially produce neutrinos  Beta decay:  Example: Nuclear reactors, Beta beams  Pion decay:  From accelerators:  Muon decay:  Muons produced by pion decays! Neutrino Factory Muons, neutrinos Possible LBL neutrino sources Protons TargetSelection, focusing Pions Decay tunnel Absorber Neutrinos Superbeam

10 Example: Neutrino Factory International Design Study (IDS-NF)  IDS-NF: Initiative from ~ to present a design report, schedule, cost estimate, risk assessment for a neutrino factory  Vision? Staged approach towards high-energy frontier (  muon collider) (Geer, 1997; de Rujula, Gavela, Hernandez, 1998; Cervera et al, 2000) Signal prop. sin 2 2  13 Contamination  magnetized detector! Muons decay in straight sections of a storage ring

11 The new paradigm: Precision?  CP violation performance represents only two possible values of  CP (0 and  )  Need new performance indicators, e. g.  Reveals that some experiments (narrow beam spectra!) strongly optimized for CPV (Coloma, Donini, Fernandez-Martinez, Hernandez, 2012) Bands:  13 allowed ranges C2P = LBNO: CERN-Pyhäsalmi L~2300 km, 100kt liquid argon 11  Talk by Diwan

The critical issue for large  13 : Systematics?

13 Fluxes and cross sections: Superbeam, beta beam (illustrated)  Superbeam  Beta beam Near detector Disappearance AppearanceFar detector Flux F 1 Near detector Disappearance AppearanceFar detector Flux F 2 ? ? BB+SPL

14 Fluxes and cross sections: Neutrino Factory  Muon (anti)neutrino cross sections measured in self-consistent way  Fluxes in and fully correlated (Tang, Winter, PRD 80, , 2009)

15 The big unknown: Systematics  New treatment needed  Use explicit near-far detector simulations  Use same knowledge for cross sections for all experiments  Define ranges for systematical errors: optimistic-default-conservative  Use identical framework for systematics implementation/correlations  Define reasonable ranges for experiment-dependent systematics: (Coloma, Huber, Kopp, Winter, arXiv: )

16 Long-baseline options  Setup table (Coloma, Huber, Kopp, Winter, arXiv: ) + Daya Bay

17 Precision: Worldwide comparison CKM phase (bands: systematics opt.-cons.) (Coloma, Huber, Kopp, Winter, arXiv: ) The Neutrino Factory is the only instrument which can measure  CP with a precision comparable to the quark sector NF10 BB350 WBB T2HK

18 Interesting alternatives  Comparison at default systematics: (Coloma, Huber, Kopp, Winter, arXiv: ) NF5 exhibits strong dependence on  CP (some dependence on binning!) BB100+SPL is the only setup comparable with NuFact

19 Critical impacts? (Coloma, Huber, Kopp, Winter, arXiv: ) Robust wrt systematics Main impact: Matter density uncertainty Operate in statistics- limited regime Exposure more important than near detector or systematics  MICA? Neutrino Factory High-E superbeam Low-E (QE!) superbeam QE e X-sec critical: no self-consistent measurement Theory: e /  ratio? Experiment: STORM?

Long-baseline alternatives with new technologies?

21 Superbeam CERN-LENA?  Main impact factors:  Neutral current backgrounds versus efficiency  Fiducial volume (cost?)  To be studied?  Background migration (no migration matrices yet? NC backgrounds reconstructed in energy window of signal)  Combination with liquid argon? L ~ 2300 km 100 kt liquid argon 100 kt LENA 90% eff. 10% NC 50 kt LENA 90% eff. 10% NC 50 kt LENA 90% eff. 30% NC 50 kt LENA 50% eff. 10% NC  Talks by Wurm, Hellgartner (special thanks: Pilar Coloma)

22 Beam to South Pole?  Probability for L=11810 km (CERN/FNAL/JHF-South Pole) (Parametric enhancement: Akhmedov, 1998; Akhmedov, Lipari, Smirnov, 1998; Petcov, 1998) Core resonance energy Mantle resonance energy Param. enhance- ment Threshold effects expected at: 2 GeV4-5 GeV Naive L/E scaling does not apply! Parametric enhancement through mantle-core-mantle profile of the Earth. Unique physics potential! !

23 IceCube/DeepCore upgrades?  Fill in IceCube/DeepCore array with additional strings  Drive threshold to lower energies  PINGU (“Precision IceCube Next Generation Upgrade“): LOI in preparation  Modest cost ~30-50M$ (dep. on no. of strings)  Two season deployment anticipated: 2015/2016/2017  A megaton-class detector at a few GeV (param. enhancement)  Further upgrades being discussed (MICA) (PINGU, 12/2012)  Talks by Kowalski

24 Example: Low-intensity superbeam?  Use existing equipment (Fermilab main injector), new beam line  Here: use most conservative assumption NuMI beam, pot (total), neutrinos only [compare to LBNE: pot without Project X ~ factor four higher exposure than the one considered here] (FERMILAB-PROPOSAL-0875, NUMI-L-714)  Low intensity may allow for shorter decay pipe (< 600M$ ?)  Advantage: Peaks in exactly the right energy range for the parametric enhancement/core effect M. Bishai PePe

25 Mass hierarchy: Event rates Normal hier.Inv. hierarchy Signal Backgrounds: e beam (irreducible) 3959 Track mis-ID (20%)  appearance (below production threshold!) 34 Neutral currents (irred.) 2479 Total backgrounds Total signal+backg (Daya Bay best-fit) >18  (stat. only)

26 NuMI-like beam to PINGU?  Very robust mass hierarchy measurement (as long as either some energy resolution or control of systematics); no directional information needed (Daya Bay best-fit; current parameter uncertainties, minimized over) GLoBES 2012 All irreducible backgrounds included

27 Potential for  CP ? NH L=11810 km  Energy resolution prerequisite:

28 Upgrade path towards  CP ?  Measurement of  CP in principle possible, but challenging  Requires:  Electromagnetic shower ID (here: 1% mis-ID)  Energy resolution (here: 20% x E)  Volume upgrade (here: ~ factor two)  Project X  Performance and optimization of PINGU and MICA requires further study = LBNE + Project X! Tang, Winter, JHEP 1202 (2012) 028 same beam to MICA?

29 Matter density measurement Example: LBNE-like Superbeam  Precision ~ 0.5% (1  ) on core density  Complementary to seismic waves Tang, Winter, JHEP 1202 (2012) 028 (Alan Jones, 1999)

Comments on sterile neutrinos

31 Evidence for sterile neutrinos?  LSND/MiniBooNE  Reactor+gallium anomalies  Global fits  Cosmology Neutrino 2012) (B. Fleming, TAUP 2011) (e. g. Kopp, Maltoni, Schwetz, )

32 Example: 3+1 framework  Well known tension between appearance and disapp. data (appearance  disapp. in both channels)  Need one or more new experiments which can test  e disappearance (Gallium, reactor anomalies)   disappearance (overconstrains 3+N frameworks)  e -  oscillations (LSND, MiniBooNE)  Neutrinos and antineutrinos separately (CP violation? Gallium vs reactor?)  QE electron neutrino and antineutrino cross sections (T2HK!)  Example: STORM - Neutrinos from STORed Muons (LOI: arXiv: ) can do it all! Summary of options: Appendix of white paper arXiv: MiniBooNE

33 Conclusions  The precision measurement of  CP requires a new dedicated long-baseline experiment  Such an experiment can (typically) also measure the mass hierarchy; however, there are alternatives  The critical impact factors for  CP are:  Exposure (high-E superbeam)  Electron neutrino cross sections (low-E superbeam, beta beam)  Matter density uncertainty (Neutrino Factory)  Alternatives require further study. Examples:  Beam to South Pole (MICA?)  Beam to LENA

BACKUP

35 New performance indicator (Coloma, Huber, Kopp, Winter, arXiv: )

36 Impact of implementation  Gray (eff. systematics, 0-10%) versus color (new):  More precise predictions for Neutrino Factory (bands: conservative – optimtistic, curves: default)  Systematic offset for T2HK, BB350 (QE e cross sec. issue) (Coloma, Huber, Kopp, Winter, arXiv: )

37 NuFact vs. BB+SPL (Coloma, Huber, Kopp, Winter, arXiv: ) Near detectors not so important if disappearance information from FD and three-flavor framework valid Exception: NF5 (main impact)

38 Mass hierarchy using existing equipment?  90% CL, existing equipment  3 , Project X and T2K with proton driver, optimized neutrino-antineutrino run plan Huber, Lindner, Schwetz, Winter, JHEP 11 (2009) 44