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Optimization of Neutrino Factory Oscillation Experiment: Overview and Strategies

This detailed paper explores optimization strategies for a neutrino factory oscillation experiment, focusing on detector improvements, channel requirements, phenomenology analysis, and resolving degeneracies. The study delves into methods like using silver and platinum channels, enhanced detectors, and baseline configurations to achieve more accurate measurements.

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Optimization of Neutrino Factory Oscillation Experiment: Overview and Strategies

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  1. Optimization of a neutrino factory oscillation experiment 3rd ISS MeetingRutherford Appleton Laboratory, UKApril 25-27, 2006 Walter Winter Institute for Advanced Study, Princeton

  2. Contents • Introduction • Optimization summary: L-Em • Improved detector summary • Channel requirements • Some phenomenology: Why are other channels useful? • Platinum • Silver • Where to concentrate the efforts? Synergies?How does the optimal neutrino factory look like? • Comparison to beta beams • Summary See my talk(s) at KEK andPatrick’s talk in Boston ISS RAL NuFact - Walter Winter

  3. Appearance channels • Complicated, but all interesting information there: q13, dCP, mass hierarchy (via A) (Cervera et al. 2000; Freund, Huber, Lindner, 2000; Freund, 2001) ISS RAL NuFact - Walter Winter

  4. Correlations and degeneracies • Connected (green) or disconnected (yellow) degenerate solutions (at a chosen CL) in parameter space • Affect performance of appearance measurements. For example, q13 sensitivity (Huber, Lindner, Winter, 2002) • Discrete degeneracies: (also: Barger, Marfatia, Whisnant, 2001)Intrinsic (d,q13)-degeneracy (Burguet-Castell et al, 2001)sgn-degeneracy (Minakata, Nunokawa, 2001)(q23,p/2-q23)-degeneracy (Fogli, Lisi, 1996) ISS RAL NuFact - Walter Winter

  5. NF-Strategies to resolve degeneracies • Combine with “silver channels” ne -> nt (Donini, Meloni, Migliozzi, 2002; Autiero et al, 2004) • Combine with “platinum channels” nm -> ne(sin22q13 > 10-3 ? Depends on BG-level!)(Boston workshop: Patrick’s talk) • Better detectors: Higher energy resolution, higher efficiencies atlow energies (CID!) (discussed at KEK, Boston) • Second NF baseline: “Magic baseline” (sin22q13 > 10-4)(Lipari, 2000; Burguet-Castell et al, 2001; Barger, Mafatia, Whisnant, 2002; Huber, Winter, 2003; others) • Other possibilities? How much doeswhat help? Where to concentratethe efforts? ISS RAL NuFact - Walter Winter

  6. Optimization of a neutrino factory 4 yr x 1.06 1021m+ decays + 4 yr x 1.06 1021m- decays Detector: 50 kt magnetized iron calorimeter ISS-values? 100 kt, 5+5 years running time = factor 2.36 luminosity increase for 1021 useful decays/year Most of the following work is done in collaboration with P. HuberM. LindnerM. Rolinec

  7. Optimization summary: L-Em • Example: q13 sensitivity relative to minimum in each plot (5s – new!) • “Magic baseline” good degeneracy resolver • L ~ 2000 – 4000 kmgood for statistics • Em > 40 GeV • At 5s very robust to • Threshold effects • Dm312 larger • Luminosity (Huber, Lindner, Rolinec, Winter, to appear) ISS RAL NuFact - Walter Winter

  8. CP violation and mass hierarchy • L ~ 3000 – 5000 km good for CP violation (large q13 : 1500 – 6000) • L > 6000 km necessary for mass hierarchy (if small q13) • Use 4000 and 7500 km (“magic baseline”) as standard baselines CP violation Mass hier. ISS RAL NuFact - Walter Winter

  9. Improved (golden) detector summary • Better energy resolution?Was: 0.15 x E (approximation) Improve to: ? • Lower appearance threshold?Was: 4 GeV, linearly climbing to maximum at 20 GeVImprove to: Max. already at 1 GeV? • CC/NC Backgrounds: Assume BG fraction b x E-2 such that ~ 5 x 10-6 integrated over spectrum (b ~ 10-3) • Background increases at low energies • Even if CID improved, NC background limits performance! (Fig. from Huber, Lindner, Winter, 2002; Gray curve from Cervera et al, 2000) (Cervera et al, 2000) ISS RAL NuFact - Walter Winter

  10. Improved detector: MH and CP violation • Improved detector would be excellent degeneracy resolver! • Also: Em = 20 GeV possible (while 50 GeV do not harm) Blue shading:Optimization potential: Golden* ISS RAL NuFact - Walter Winter

  11. Improved detector: Systematics Preliminary • CP violationmeasurement veryrobust with respectto systematics (signal normalization error) andBG level as long as b << 10-2 • Note that 20% BG uncertainty assumed Standard“improved” detector ISS RAL NuFact - Walter Winter

  12. Systematics: Leading atm. parameters Preliminary • For Dm312 systematics somewhat important Dashed:10% error onsolar params • Energy resolution important for leading atm. parameters • Systematics somewhat important for Dm312, but impact of solar input much larger ISS RAL NuFact - Walter Winter

  13. Channel requirements: Phenomenology Assume specific hierarchy • Antineutrinos: • Magic baseline: • Silver: • Platinum: (Akhmedov, Johansson, Lindner, Ohlsson, Schwetz, 2004) ISS RAL NuFact - Walter Winter

  14. Platinum channel • Changes sign of CP-odd term • Compare to antineutrinos: • Antineutrino channel without matter effect suppression/enhancement (dep. on hierarchy) • Support information on dCP for large q13? ISS RAL NuFact - Walter Winter

  15. Platinum channel: Assumptions • Electron detection properties are MINOS-like (NuMI note NuMI-L-714) • 2.5 GeV threshold • 40% efficiency • Energy resolution 0.15 x E • 1% BG from all neutral current events • 1% BG from charge identification • Fiducial detector mass: same as “golden” mass • Matter density uncertainty: Correlated with golden channel • If platinum is possible, use it in all “golden” detectors, such as for NuFact+NuFact@MB at both places! Limits the q13for which thischannel is useful! ISS RAL NuFact - Walter Winter

  16. Platinum channel: Results Preliminary Golden+Platinum Golden+Platinum Golden Golden BG-dominated • Good degeneracy resolver; especially for large q13! ISS RAL NuFact - Walter Winter

  17. Silver channel • Changes sign of CP-even and CP-odd terms • Here: we only test maximal mixing • Interesting for matter density correlation:2nd and 3rd terms fully correlated/anticorrelated with matter density uncertainty from 1st term(if same matter profile as golden channel) ISS RAL NuFact - Walter Winter

  18. Silver channel: Assumptions • Emulsion cloud chamber a la OPERA(Autiero et al, 2004) • Threshold starting at 2.5 GeV (Fig. 7, Autiero et al, 2004) • Energy resolution 0.20 x E (optimistic?) • 10 kt fiducial mass • Only neutrinos detected • Matter density uncertainty: Correlated with golden channel if at same baseline • Also: Test improved Silver* with 5 x Signal, 3 x BG(if all leptonic and hadronic t decay channels could be measured?) (Migliozzi, private communication) ISS RAL NuFact - Walter Winter

  19. Silver channel: Options • Which baseline? • Same as golden channel + correlated matter effect • Different from golden channel + uncorrelated matter effect (e.g., L=732 km) • Main results (qualitatively): • Muon energies should probably not be too low (higher tau production threshold!) • Silver channel hardly affects golden channel opt. • Correlated matter effect helps and makes 4000 + 4000 km attractive ISS RAL NuFact - Walter Winter

  20. Silver channel: Results and comparison Preliminary • Matter density correlation helps • Silver without upgrades not competitive to platinum • Silver* at “golden” baseline complementary to platinum Effect ofcorrelatedmatter effect ISS RAL NuFact - Walter Winter

  21. Better detector vs. new channels Preliminary • Better detector = increase reach by improved statistics/energy info • Different channel = resolve degs by complementary information ISS RAL NuFact - Walter Winter

  22. Overall picture: Comparison matrix ISS RAL NuFact - Walter Winter

  23. Comparison matrix: Explanations Synergies:Comparablestatistics Detector degree of freedom Directcomparison ofoptions at samebaseline Accelerator degree of freedom Overall effort Optimized detector, additional channel, or increased luminosity increase “detector effort” by oneBaseline: 4000 km, unless different one in index (MB=“Magic baseline”). Muon energy: 50 GeVStars: Improved golden detector; in any star option the muon energy is 20 GeV ISS RAL NuFact - Walter Winter

  24. “Simple” options • No surprises: L=4000 km good for CP violation,L=7500 km good for mass hierarchy • Beta beam very good for CP violation, but cannot measure mass hierarchy for small q13 ISS RAL NuFact - Walter Winter

  25. Synergies for detector effort “two” Compare with each other: If similar impact,concentrate on better one? (Thick curves: two baselines) • Synergies and optimal performance in “competing regions” for Golden*, Golden+Platinum, Golden+(Golden)MB • NEW: Magic baseline helps for large q13! Compare to (Golden)2L:If better in some region, real synergy effect! ISS RAL NuFact - Walter Winter

  26. Physics case: Large sin22q13 Discovery reaches for: • For large q13, only CP violation an issue • Beta beam best option even after optimization CP violation (3s) Mass hierarchy (3s) sin22q13 (5s) ISS RAL NuFact - Walter Winter

  27. Physics case: Interm. sin22q13 • “Typical” physics case for a neutrino factory!? • Improved detector and magic baseline sufficient to make physics case against beta beam for any performance indicator used here ISS RAL NuFact - Walter Winter

  28. Physics case: Small sin22q13 • Clear physics case for neutrino factory even with “moderate” improvements • Optimal reach for improved detector and magic baseline • Beta beam cannot determine masshierarchy ISS RAL NuFact - Walter Winter

  29. Where to concentrate the efforts? • Optimized NuFact: Measure mass hierarchy and CP violation almost down to sin22q13 = 10-5! (including all degeneracies, for maximal mixing, 3s) ISS RAL NuFact - Walter Winter

  30. Comparison to beta beams Preliminary Assumptions: • 2.9 10186He decays/year1.1 101818Ne decays/year at simultaneous operation for eight years(or double ion decays/year) • g=350, L=730 km, 500 kt WCMaximum at CERN?(Burguet-Castell et al, 2005) • g=1000, L=1300 km, 50 kt TASDHigh end. Optimal for CP violation(Huber, Lindner, Rolinec, Winter, 2005) • g=1000, L=2600 km, 50 kt TASDHigh end. Optimal for mass hierarchy(Huber, Lindner, Rolinec, Winter, 2005) • g=1000, L=1300 km + 2600 kmWhy not two baselines similar to NuFact? ISS RAL NuFact - Walter Winter

  31. Comparison to beta beams (2) Preliminary • NF good for q13 discovery, MH discovery and dCP for small q13 • Beta beam competitive for CP violation (large q13); But: Extreme effort to measure MH if q13 small could make physics case difficult! ISS RAL NuFact - Walter Winter

  32. Summary • Physics case for neutrino factory for small/intermediate sin22q13 established; no clear physics case for large q13 yet(baseline reopt. and reduced matter density uncertainties help somewhat …) • The optimal neutrino factory has (at least) • Two baselines with golden channel detectors • A golden detector as optimized as possible • Electron neutrino detection in all golden detectors • The silver channel could be interesting if • Improved efficiencies (more tau decay channels) • Correlated matter effects (put detector to golden baseline) • Specific physics case (non-maximal mixing, unitarity test etc.) ISS RAL NuFact - Walter Winter

  33. (Our) plans • Refine systematics/BG impact study • Check what one has to do for improved leading atm. parameter measurements • Re-check silver channel baseline optimization:732 km? Both at same baseline? Change ofoptimization? Muon energies? • Test impact of matter density uncertaintiesafter (correlated) platinum/silver channels • Possibly some work on large q13 case • Finish this analysis (writeup as paper) ISS RAL NuFact - Walter Winter

  34. Additional slides

  35. MINOS: Larger value of Dm312? • No qualitative changes in L-E-optimization,but improved absolute reaches! • Physics case for magic baseline even stronger • Example: 0.003 eV2 ISS RAL NuFact - Walter Winter

  36. Better detector: q13 sensitivity • High CL chosen (4s):avoid threshold effects(q13,dCP)-degeneracy affects sensitivity limitat L ~ 1500-5000 km • Better detector threshold:L=2000-3000 km most attractive q13-baseline “Magicbaseline” Preliminary ISS RAL NuFact - Walter Winter

  37. Better detector: Large q13 Preliminary • Both better Eres and threshold useful • Both better detector and smaller matter density uncertainty useful • Either or combination sufficient to compete with the superbeam upgrades (prel.) • Large Dr+better detector prefers shorter baselines (1000-2000km); Em small OK No dCP at Lmagic! ISS RAL NuFact - Walter Winter

  38. Better detector in L-E-space: q13 sens. • 3s sensitivity to sin22q13 Better Eres Better threshold Better Eres+thresh. Preliminary (Huber, Lindner, Rolinec, Winter, to appear) ISS RAL NuFact - Walter Winter

  39. Better detector in L-E-space: Large q13 • CP fraction for CP violation (3s):“Standard”“Optimal appearance”L=1000 km/Em=20 GeVpossible alternative? Preliminary (Huber, Lindner, Rolinec, Winter, to appear) ISS RAL NuFact - Walter Winter

  40. Silver channel: Optimal baseline? Preliminary • Correlated matter effect with LECC=4000 km better than any other baseline (except q13 sensitivity for L ~ 1500 km) ISS RAL NuFact - Walter Winter

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