1. A neutrino beam to IceCube/PINGU? (PINGU = “Precision IceCube Next-Generation Upgrade“) NPAC (Nuclear/Particle/Astro/Cosmo) Forum UW-Madison, USA May 15, 2012 Walter Winter Universität Würzburg TexPoint fonts used in EMF: AAAAA A A A

2. 2 Contents  Introduction  Oscillation physics using a core-crossing baseline  Neutrino beam to PINGU: Beams and detector parameterization  Detector requirements for large  13  Comments on LBNE reconfiguration  Summary

3. 3 Three flavor mixing  Use same parameterization as for CKM matrix Pontecorvo-Maki-Nakagawa-Sakata matrix ( ) ( ) ( ) =xx (s ij = sin  ij c ij = cos  ij ) Potential CP violation ~  13

4. 4  13 discovery 2012  First evidence from T2K, Double Chooz  Discovery (~ 5  ) independently (?) by Daya Bay, RENO (from arXiv:1204.1249) 1  error bars Daya Bay 3 

5. 5 Mass spectrum/hierarchy  Specific models typically come together with specific MH prediction (e.g. textures are very different)  Good model discriminator (Albright, Chen, hep-ph/0608137) 8 8 NormalInverted

6. 6  Three flavors: 6 params (3 angles, one phase; 2 x  m 2 )  Describes solar and atmospheric neutrino anomalies, as well as reactor antineutrino disapp.! Three flavors: Summary Coupling :  13 Atmospheric oscillations: Amplitude:  23 Frequency :  m 31 2 Solar oscillations : Amplitude:  12 Frequency :  m 21 2 Suppressed effect :  CP (Super-K, 1998; Chooz, 1999; SNO 2001+2002; KamLAND 2002; Daya Bay, RENO 2012)

7. 7 Consequences  Parameter space for  CP starts to become constrained; MH/CPV difficult (need to exclude  CP =0 and  )  Need new facility! Huber, Lindner, Schwetz, Winter, 2009

8. 8 Mass hierarchy discovery?  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

9. 9 Mass hierarchy measurement?  Mass hierarchy [sgn(  m 2 )] discovery possible with atmospheric neutrinos? (liquid argon, HyperK, MEMPHYS, INO, PINGU?, LENA?, …) Barger et al, arXiv:1203.6012; IH more challenging  However: also long-baseline proposals! (LBNO: superbeam ~ 2200 km – LAGUNA design study; CERN-SuperK ~ 8870 km – Agarwalla, Hernandez, arXiv:1204.4217; South Pole: Dick et al, 2000) Perhaps different facilities for MH and CPV proposed/discussed?

10. Oscillation physics using a core-crossing baseline

11. 11 What is PINGU? 2012

12. 12 PINGU fiducial volume?  A few Mt fiducial mass for superbeam produced with FNAL main injector protons (120 GeV) (Jason Koskinen) LBNE- beam

13. 13 Beams to PINGU?  Labs and potential detector locations (stars) in “deep underground“ laboratories: (Agarwalla, Huber, Tang, Winter, 2010) FNAL-PINGU: 11620 km CERN-PINGU: 11810 km RAL-PINGU: 12020 km JHF-PINGU: 11370 km All these baselines cross the Earth‘s outer core!

14. 14 Matter profile of the Earth … as seen by a neutrino (PREM: Preliminary Reference Earth Model) Core Inner core

15. 15 Matter effect (MSW)  Ordinary matter: electrons, but no ,   Coherent forward scattering in matter: Net effect on electron flavor  Hamiltonian in matter (matrix form, flavor space): Y: electron fraction ~ 0.5 (electrons per nucleon) (Wolfenstein, 1978; Mikheyev, Smirnov, 1985)

16. 16 Parameter mapping  Oscillation probabilities in vacuum: matter: Matter resonance: In this case: - Effective mixing maximal - Effective osc. frequency minimal For  appearance,  m 31 2 : -  ~ 4.7 g/cm 3 (Earth’s mantle): E res ~ 6.4 GeV -  ~ 10.8 g/cm 3 (Earth’s outer core): E res ~ 2.8 GeV Resonance energy:  MH

17. 17 Mantle-core-mantle profile  Probability for FNAL-PINGU (numerical) (Parametric enhancement: Akhmedov, 1998; Akhmedov, Lipari, Smirnov, 1998; Petcov, 1998) Core resonance energy Mantle resonance energy Inter- ference Threshold effects expected at: 2 GeV4-5 GeV Beam energy and detector threshold have to pass ~ 2 GeV! Naive L/E scaling does not apply! Parametric enhancement through mantle-core-mantle profile of the Earth. Unique physics potential! !

18. Neutrino beam to PINGU? Beams and detector parameterization

19. 19 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 neutrino sources Protons TargetSelection, focusing Pions Decay tunnel Absorber Neutrinos Superbeam

20. 20 Considered setups (for details: Tang, Winter, JHEP 1202 (2012) 028, arXiv:1110.5908; Sec. 3)  Single baseline reference setups:  Idea: similar beam, but detector replaced by PINGU/MICA [need to cover ~ 2 – 5 GeV]: L [km]

21. 21 Want to study e -  oscillations  Beta beams:  In principle best choice for PINGU (need muon flavor ID only)  Superbeams:  Need (clean) electron flavor sample. Difficult?  Neutrino factory:  Need charge identification of  + and  - (normally) Oscillation channels

22. 22 PINGU fiducial volume?  In principle: Mton-size detector in relevant ranges:  Unclear how that evolves with cuts for flavor-ID etc. (background reduction); MICA even larger?  Use effective detector parameterization to study requirements: E th, V eff, E res (Tang, Winter, JHEP 1202 (2012) 028; V eff somewhat smaller than J. Koskinen ‘s current results) E th V eff E res (  E) =  E

23. 23 Detector paramet.: mis-ID misIDtracks << misID <~ 1 ? (Tang, Winter, JHEP 1202 (2012) 028) misID: fraction of events of a specific channel mis-identified as signal

24. Detector requirements for large  13

25. 25 Superbeam (LBNE-like)  Mass hierarchy measurement very robust (even with large misID and total rates only possible) (Tang, Winter, JHEP 1202 (2012) 028) (misIDtracks = 0.01) Fraction of  CP

26. 26 Low-intensity alternative?  Use existing equipment, new beam line  Here: use most conservative assumption NuMI beam, 10 21 pot (total), neutrinos only [compare to LBNE: 22+22 10 20 pot without Project X ~ factor four higher exposure than the one considered here] (FERMILAB-PROPOSAL-0875, NUMI-L-714)  Low intensity allows for shorter decay pipe (rough estimate: ~ 100 m for 700kW beam)  Advantage: Peaks in exactly the right energy range for the parametric enhancement due to the Earth‘s core (Tang, Winter, JHEP 1202 (2012) 028)

27. 27 Detector parameterization  Challenges:  Electron flavor ID  Systematics (efficiency, flux normalization  near detector?)  Energy resolution  Make very (?) conservative assumptions here:  Fraction of mis-identified muon tracks (muon tracks may be too short to be distinguished from signal) ~ 20%  Irreducible backgrounds (zeroth order assumption!):  Intrinsic beam background  Neutral current cascades     cascades (hadronic and electromagnetic cascades indistinguishable)  Systematics uncorrelated between signal and background  No energy resolution (total rates only) (for details on parameterization: Tang, Winter, JHEP 1202 (2012) 028)

28. 28 Event rates Normal hier.Inv. hierarchy Signal156054 Backgrounds: e beam 3959 Disapp./track mis-ID511750  appearance 34 Neutral currents2479 Total backgrounds30323292 Total signal+backg.45923346 (Daya Bay best-fit) >18  (stat. only)

29. 29 NuMI-like beam to PINGU?  Very robust mass hierarchy measurement (as long as either some energy resolution or control of systematics); track mis-identification maybe too conservative (Daya Bay best-fit; current parameter uncertainties, marginalized over) GLoBES 2012 All irreducible backgrounds included

30. 30 Probabilities:  CP -dependence  There is a rich  CP -phenomenology: (probably works for NH only!?) NH

31. 31 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)  Maybe: volume upgrade (here: ~ factor two)  Project X  Performance and optimization of PINGU, and possible upgrades (MICA, …) require further study = LBNE + Project X! (Tang, Winter, JHEP 1202 (2012) 028) same beam to PINGU

32. 32 Beta beam  Similar results for mass hierarchy measurement (easy)  CPV less promising: long L, asymmetric beam energies (at least in CERN-SPS limited case  ~656 for 8 B and  =390 for 8 Li) although moderate detector requirements (Tang, Winter, JHEP 1202 (2012) 028) (misID ~ 0.001, E th =2 GeV, E res =50% E, V eff =5 Mt)

33. 33 Neutrino factory  No magnetic field, no charge identification  Need to disentangle P e  and P  by energy resolution: (from: Tang, Winter, JHEP 1202 (2012) 028 ; for non-magnetized detectors, see Huber, Schwetz, Phys. Lett. B669 (2008) 294) )

34. 34  contamination  Challenge: Reconstructed at lower energies! (Indumathi, Sinha, PRD 80 (2009) 113012; Donini, Gomez Cadenas, Meloni, JHEP 1102 (2011) 095)  Choose low enough E  to avoid   Need event migration matrices (from detector simulation) for reliable predictions! (neutral currents etc) (sin 2 2  13 =0.1) (Tang, Winter, JHEP 1202 (2012) 028)

35. 35 Matter density measurement Example: LBNE-like Superbeam  Precision ~ 0.5% (1  )  Highly competitive to seismic waves (seismic shear waves cannot propagate in the liquid core!) (Tang, Winter, JHEP 1202 (2012) 028)

36. LBNE reconfiguration (some personal comments) Thanks discussions with: A. de Gouvea, F. Halzen, J. Hylen, B. Kayser, J. Kopp, S. Parke, PINGU collaboration, …

37. 37  ~ 600M$

38. 38 Landscape (before reconfiguration)  LBNE one out of many options to measure CPV  Can this reach be matched in a phased approach?  How can one define a truly unique experiment for <= 600M US$?  How would one react if T2HK happens? (P. Huber)

39. 39 Reconfiguration options? … or how to spend 600 M$  New detector, existing beam line  MINOS site (L=735 km)  NOvA site (L=810 km)  New site?  New (smaller) detector, new beam line (~300 M$)  Smaller detector in Homestake (L=1300 km)  Surface detector at Homestake (L=1300 km)  New beam line (<= 550 M$?), (then) existing detector  PINGU (L=11620 km) …… Idea ~ 2 weeks old

40. 40 Best physics concept? (Barger, Huber, Marfatia, Winter, PRD 76 (2007) 053005) NuMI beam line New beam line Homestake, on-axis

41. 41 Conclusion: LBNE – smaller version?  How many  does one need?  Combination of experiments tolerable as physics result? MH, 5  This is what T2HK cannot do This is what T2HK can also do

42. 42 Conclusions: FNAL-PINGU?  FNAL-PINGU  Megaton-size ice detector as upgrade of DeepCore with lower threshold; very cost-efficient compared to liquid argon, water  Unique mass hierarchy measurement through parameteric enhancement; proton beams from main injector may just have right energy  In principle, MH even with counting experiment measurable (compared to MH determination using atmospheric neutrinos)  Challenges on beam side (questions from PINGU meeting):  Tilt of beam line – feasibility, cost?  Near detector necessary? Maybe not, if 10% systematics achievable …  Beam bunching (to reduce atmospheric backgrounds)? NB: very low exposure required for MH; shorter decay pipe, one horn only, …?  Perspectives  CP violation challenging (requires energy resolution, flavor identification), but not in principle excluded; needs further study on detector side  Measurement of Earth‘s core density, in principle, possible (Tang, Winter, JHEP 1202 (2012) 028)  Upgrades of PINGU discussed (MICA)  Truly unique and spectacular long-baseline experiment with no other alternative proposed doing similar physics!?  The LBNE alternative if T2HK is going to be funded?

43. BACKUP

44. 44 NOvA+INO (atm.)? (Blennow, Schwetz, arXiv:1203.3388) MH, 3 

45. 45 NF: Precision measurements? … only if good enough energy resolution ~ 10% E and misID (cascades versus tracks) <~ 1% can be achieved! Requires further study … (Tang, Winter, JHEP 1202 (2012) 028)

46. 46 Beams: Appearance channels (Cervera et al. 2000; Freund, Huber, Lindner, 2000; Akhmedov et al, 2004)  Antineutrinos:  Magic baseline: L~ 7500 km: Clean measurement of  13 (and mass hierarchy) for any energy, value of oscillation parameters! (Huber, Winter, 2003; Smirnov 2006) In combination with shorter baseline, a wide range of very long baseline will do! (Gandhi, Winter, 2006; Kopp, Ota, Winter, 2008)

47. 47 Quantification of performance Example: CP violation discovery Sensitive region as a function of true  13 and  CP  CP values now stacked for each  13 Read: If sin 2 2  13 =10 -3, we expect a discovery for 80% of all values of  CP No CPV discovery if  CP too close to 0 or  No CPV discovery for all values of  CP 33 ~ Precision in quark sector! Best performance close to max. CPV (  CP =  /2 or 3  /2)

48. 48 Effective volume  Difference E th = 2 GeV, V eff =5 Mt to actual (energy-dependent) fiducial volume: (Tang, Winter, JHEP 1202 (2012) 028)

49. 49 Note: Pure baseline effect! A 1: Matter resonance VL baselines (1) (Factor 1) 2 (Factor 2) 2 (Factor 1)(Factor 2) Prop. To L 2 ; compensated by flux prop. to 1/L 2

50. 50  Factor 1: Depends on energy; can be matter enhanced for long L; however: the longer L, the stronger change off the resonance  Factor 2: Always suppressed for longer L; zero at “magic baseline” (indep. of E, osc. Params) VL baselines (2) (  m 31 2 = 0.0025,  =4.3 g/cm 3, normal hierarchy)  Factor 2 always suppresses CP and solar terms for very long baselines; note that these terms include 1/L 2 -dep.!