Geographical issues and physics applications of “very long” neutrino factory baselines

1. Geographical issues and physics applications of “very long” neutrinofactory baselines NuFact 05 June 23, 2005 Walter Winter Institute for Advanced Study, Princeton

2. Contents • Introduction • What are “very long” baselines? • Applications of very long baselines • Detector sites for very long baselines • Summary NuFact 05 - VLBL - Walter Winter

3. Picture of three-flavor oscillations Atmosphericoscillation:Amplitude: q23Frequency: Dm312 Solaroscillation:Amplitude: q12Frequency: Dm212 Sub-leading effect: dCP Coupling strength: q13 Magnitude of q13 is key to “subleading” effects: • Mass hierarchy determination • CP violation nm ne flavor transitions on atmospheric oscillation scale NuFact 05 - VLBL - Walter Winter

4. Appearance channels: nmne • All interesting information there: q13, dCP, mass hier. • Complicated: Problems with correlations and degs (Cervera et al. 2000; Freund, Huber, Lindner, 2000; Freund, 2001) NuFact 05 - VLBL - Walter Winter

5. Neutrino factory (from: CERN Yellow Report ) • Ultimative “high precision” instrument!? • Muon decays in straight sections of storage ring • Decay ring naturally spans two baselines • Technical challenges: Target power, muon cooling, maybe steep decay tunnels • Timescale: 2025? NuFact 05 - VLBL - Walter Winter

6. “Very long” (VL) baselines • Typical baseline: 3,000 km for 50 GeV neutrino factory(to measure CP violation) • Define “very long”: L >> 3,000 km • Challenge: Decay tunnel slopes! • Our benchmark neutrino factory: NuFact-II • Em = 50 GeV, L = 3,000 km (standard configuration) • Running time: 4 years in each polarity = 8 years • Detector: 50 kt magnetized iron calorimeter • 1021 useful muon decays/ year (~ 4 MW target power) • 10% prec. on solar params, 5% matter density uncertainty • Atmospheric parameters best measured by disapp. channel (for details: Huber, Lindner, Winter, hep-ph/0204352) NuFact 05 - VLBL - Walter Winter

7. Phenomenology of VL baselines (1) Note: Pure baseline effect!A 1: Matter resonance Prop. To L2; compensated by flux prop. to 1/L2 (Factor 1)(Factor 2) (Factor 1)2 (Factor 2)2 NuFact 05 - VLBL - Walter Winter

8. Phenomenology of VL baselines (2) • 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) (Dm312 = 0.0025, r=4.3 g/cm3, normal hierarchy) • Factor 2 always suppresses CP and solar terms for very long baselines; note that these terms include 1/L2-dep.! NuFact 05 - VLBL - Walter Winter

9. Application 1: “Magic baseline” • Idea:Factor 2=0 independent of E, osc. Params • Purpose: “Clean” measurement of q13 and mass hierarchy • Drawback: No dCP measurement at magic baseline • combine with shorter baseline, such as L=3 000 km • q13-range: 10-4 < sin22q13 < 10-2,where most problems with degeneracies are present NuFact 05 - VLBL - Walter Winter

10. Magic baseline: q13 sensitivity Use two-baseline space (L1,L2) with (25kt, 25kt) and compute q13 sensitivity including correlations and degeneracies: No CP violation measurement there! Animation in q13-dCP-space: Optimal performance for all quantities: Unstable: Disappears for different parameter values (Huber, Winter,PRD 68, 2003, 037301, hep-ph/0301257) NuFact 05 - VLBL - Walter Winter

11. CP coverage and “real synergies” Range of all fit values which fit a chosen simulated value of dCP Any “extra” gain beyond a simple addition of statistics • 3 000 km + 7 500 kmversus all detector mass at 3 000 km (2L) • Magic baseline allows a risk-minimized measurement (unknown d) • “Staged neutrino factory”: Option to add magic baseline later if in “bad” quadrants? (Huber, Lindner, Winter, JHEP, hep-ph/0412199) One baseline enough Two baselines necessary NuFact 05 - VLBL - Walter Winter

12. Magic baseline: Detector sites? “Hot spots”:Interesting for many labs Pyhaesalmi mine, Finland: MB from JHF Gran Sasso, Italy: MB from Fermilab China, India:MB from CERN? (http://www.sns.ias.edu/~winter/BasePlots.htm) NuFact 05 - VLBL - Walter Winter

13. Appl. 2: Matter effect sensitivity for q13=0 • Idea: For q13=0 only “solar term” survives. Factor 2 is suppressed in matter vs. vacuum : • Purpose: Verify MSW effect at high CL even for q13=0 • Drawback: No mass hierarchy measurement (this term) • q13-range: Interesting for sin22q13 < 10-3 • Note: No 1/L2 suppression of solar term in vacuum! NuFact 05 - VLBL - Walter Winter

14. MSW sensitivity: q13-L-dependence (dCP=0) • For sin22q13 >> a2 ~ 10-3:Depending on sin22q13, L=3 000 km might be sufficient • For sin22q13 << a2 ~ 10-3:Independent of sin22q13, even works forsin22q13=0:L > 6 000 km required! No sensitivity here (Winter, PLB 613, 2005, 73, hep-ph/0411309) NuFact 05 - VLBL - Walter Winter

15. MSW effect vs. mass hierarchy (5s, dashed curve: no correlations) • Both qualitatively similar for large q13,but:matter effect sens. harder(Difference vacuum-matter < difference normal-inverted) • Small q13: No mass hierarchy sensitivity whatsoever • Some dependence on dCP, but L > 6 000 km safe (Winter, PLB 613, 2005, 73, hep-ph/0411309) NuFact 05 - VLBL - Walter Winter

16. Application 3: Measurement of the Earth’s core density • Idea:Factor 1 does not drop prop. 1/L2 close to resonance • But: The longer L, the sharper the change off the resonance Very sensitive to matter density especially for large L q13 large,A~1 (resonance) • Purpose: Measure the absolute density of the Earth’s core • Drawbacks: Not possible to measure dCP; “vertical” decay tunnel sophisticated • q13-range: sin22q13 >> 10-3 NuFact 05 - VLBL - Walter Winter

17. Core density measurement: Principles • Most direct information on the matter density from Earth’s mass and rotational inertia, but: • Least sensitive to the innermost parts • Seismic waves: s-waves mainly reflected on core boundaries • Least information on inner core • No “direct” matter density measurement; depends on EOS • No “absolute” densities: mainly sensitive to density jumps • Neutrinos: Measure Baseline-averaged density: • Equal contribution of innermost parts. Measure least known innermost density! NuFact 05 - VLBL - Walter Winter

18. Core density measurement: Results (Winter, hep-ph/0502097) • First: consider “ideal” geographical setup:Measure rIC (inner core) with L=2 RE • Combine with L=3000 km to measure oscillation parameters • Key question: Does this measurement survive the correlations with the unknown oscillation parameters? • For sin22q13 > 0.01 a precision at the per cent level is realistic • For 0.001 < sin22q13 < 0.01:Correlations much worse without 3000 km baseline (1s, 2s, 3s, dCP=0, Dashed: no correlations) NuFact 05 - VLBL - Walter Winter

19. Density measurement: Geography Something else than water in “core shadow”? Inner core shadow Outer core shadow NuFact 05 - VLBL - Walter Winter

20. “Realistic geography” JHF BNL … and sin22q13=0.01. Examples for rIC: • There are potential detector locations! • Per cent level precision not unrealistic CERN (Winter, hep-ph/0502097) Inner core shadow NuFact 05 - VLBL - Walter Winter

21. 10-1 10-2 10-3 10-4 10-5 10-6 Excluded sin22q13 Summary: VL baseline applications • Major challenge: Decay ring/decay tunnel slope • Open question: Simultaneous or subsequent operation of VL baseline? Feasiblity study for storage ring configurations needed! NuFact 05 - VLBL - Walter Winter