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Neutrino Oscillation Results from MiniBooNE

Neutrino Oscillation Results from MiniBooNE. Joe Grange University of Florida. Outline. MiniBooNE motivation The experiment Oscillations Analysis Results Summary and outlook. MiniBooNE motivation The experiment Oscillations Analysis Results Summary and outlook. n Oscillations.

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Neutrino Oscillation Results from MiniBooNE

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  1. Neutrino Oscillation Results from MiniBooNE Joe Grange University of Florida

  2. Outline • MiniBooNE motivation • The experiment • Oscillations • Analysis • Results • Summary and outlook

  3. MiniBooNE motivation • The experiment • Oscillations • Analysis • Results • Summary and outlook

  4. n Oscillations Joe Grange Miami 2011 December 2011 • Neutrinos oscillate! One of the few concrete BSM results. Implications: • oscillation shape strongly supports massive n’s • n Hamiltonian eigenstates are NOT flavor eigenstates • Lepton flavor is not conserved (e ,  , e ) • Embarrassingly brief formalism: n born of type a propagates according to PMNS mixing matrix - describes mixing between n flavor state a, mass state k

  5. n Oscillations Joe Grange Miami 2011 December 2011 • Under the approximations of only two n masses and after travelling a distance L the n born as a has survival probability (detected as a) of and an oscillation probability of

  6. n Oscillations Joe Grange Miami 2011 December 2011 “Disappearance” “Appearance” Physics: qosc. amplitude; Dm2osc. frequency

  7. n Oscillations Joe Grange Miami 2011 December 2011 “Disappearance” “Appearance” Physics: qosc. amplitude; Dm2osc. frequency Experiment: E n energy, L distance from n creation to detector

  8. n Oscillations Joe Grange Miami 2011 December 2011 • Large Electron-Positron collider data: exactly 3 active, light n flavors • We also know of 3 n’s: ne,nm, nt • 3 n’s require two independent sets of Dm2 mixing

  9. n Oscillations Joe Grange Miami 2011 December 2011 This is observed and confirmed! Confirmation with Super-K, K2K and MINOS data Confirmation with SNO, Kamland data

  10. n Oscillations Joe Grange Miami 2011 December 2011 However… Evidence for high Dm2 mixing from LSND experiment some hints from cosmology and reactor data as well Confirmation with Super-K, K2K and MINOS data Confirmation with SNO, Kamland data

  11. LSND Joe Grange Miami 2011 December 2011 • LSND: Liquid Scintillator Neutrino Detector (Los Alamos, 1990s) • Evidence of ne excess in nm beam 2 nosc. fit Highly controversial! LSND excess: 87.9 ± 22.4 ± 6.0 (3.8 s)

  12. MiniBooNE motivation • The experiment • Oscillations • Analysis • Results • Summary and outlook

  13. Enter MiniBooNE! Mini Booster Neutrino Experiment Joe Grange Miami 2011 December 2011 • MiniBooNE has same L/E as LSND but different systematic errors. Quick comparison: • MiniBooNE • Neutrino beam from accelerator (decay-in-flight, average En ~ 800 MeV) • New backgrounds: nm CCQE and NC p0mis-id for oscillation search • New backgrounds: intrinsic ne from K decay (0.5% of p make K) • LSND • Neutrino beam from accelerator (decay-at-rest, average En ~ 35 MeV) • nmtoo low E to make m or p • Proton beam too low E to make K

  14. Booster Neutrino Beam Booster Target Hall decay region absorber target and horn detector FNAL Booster dirt Booster primary beam secondary beam tertiary beam (protons) (mesons) (neutrinos) Booster Neutrino Beam Joe Grange Miami 2011 December 2011 8.9 GeV/c momentum protons extracted from Booster, steered toward a beryllium target

  15. Booster Neutrino Beam decay region absorber target and horn detector FNAL Booster dirt nm Booster primary beam secondary beam tertiary beam (protons) (mesons) (neutrinos) Booster Neutrino Beam Joe Grange Miami 2011 December 2011 Magnetic horn with reversible polarity focuses either neutrino or anti-neutrino parent mesons (“neutrino” vs “anti-neutrino” mode) p- p+ p+ p-

  16. Detector Joe Grange Miami 2011 December 2011 • 6.1m radius Cherenkov detector houses 800 tons of undoped mineral oil, 1520 PMTs in two regions • Inner signal region • Outer veto region (35 cm thick) Nucl. Instr. Meth. A599, 28 (2009)

  17. Neutrino Flux Joe Grange Miami 2011 December 2011 • Flux prediction based exclusively on external data - no in situ tuning • Dedicated p production data taken by HARP collaboration, measured 8.9 GeV/c on MiniBooNE replica target p- production HARP collaboration, Eur. Phys. J. C 52 29 (2007)

  18. Neutrino Flux Joe Grange Miami 2011 December 2011 • Combining HARP data with detailed Geant4 simulation gives the flux prediction at the MiniBooNE detector for positive and negative focusing horn polarities MiniBooNE collaboration, Phys. Rev. D 79, 072002 (2009)

  19. A BooNE of Data Joe Grange Miami 2011 December 2011 • Stable running since 2002 • POT received from Booster: • 6.4 × 1020 in n mode • 8.6 × 1020 in n mode (analyzed), ~30% more data coming!

  20. MiniBooNE motivation • The experiment • Oscillations • Analysis • Results • Summary and outlook

  21. Particle ID Basics Joe Grange Miami 2011 December 2011 • PID based almost exclusively on timing and topology of PMT hits

  22. E light t,x,y,z Particle ID Analysis Joe Grange Miami 2011 December 2011 • Form charge and timing PDFs, fit for track parameters under 3 hypotheses • Electron • Muon • Superposition of two g’s from p0 decay • Apply energy-dependent cuts on L(e/m), L(e/p) and p0 mass to search for single electron events • Plot events passing cuts as a function of reconstructed ne energy and fit for two-n oscillations

  23. Backgrounds Joe Grange Miami 2011 December 2011 intrinsic mis-id Signal interaction ne CCQE: ne + n -> e- + p , observe single e- Intrinsic ne from m originate from same p as nm CCQE sample Measuring nm CCQE channel constrains intrinsic ne from p -> m -> edecay

  24. Backgrounds Joe Grange Miami 2011 December 2011 intrinsic mis-id ne from m± Signal interaction ne CCQE: ne + n -> e- + p , observe single e- Intrinsic ne from m originate from same p as nm CCQE sample Measuring nm CCQE channel constrains intrinsic ne from p -> m -> edecay

  25. Backgrounds Joe Grange Miami 2011 December 2011 intrinsic mis-id νe from K±, K0 At high energy,nmflux is dominated by K production MeasuringnmCCQE at high energy constrains kaon production, and thus intrinsicnefrom K Also use external measurements from HARP • Sanford-Wang fits to world K+/K0 data

  26. } Phys. Rev. D81, 013005 (2010) Backgrounds Joe Grange Miami 2011 December 2011 intrinsic mis-id mis-ID π0 Measured in MiniBooNE

  27. Backgrounds Joe Grange Miami 2011 December 2011 intrinsic mis-id mis-id Δ About 80% of our NC π0 events come from resonant Δproduction Constrain Δ→Nγ by measuring the resonant NC π0 rate, apply known branching fraction to N, including nuclear corrections

  28. Backgrounds Joe Grange Miami 2011 December 2011 intrinsic mis-id dirt events Come from ν events in surrounding dirt Pileup at high radius and low E Fit dirt-enhanced sample to extract dirt event rate with 10% uncertainty

  29. Backgrounds Joe Grange Miami 2011 December 2011 intrinsic Every major source of background can be internally constrained by MiniBooNE. mis-id dirt events Come from ν events in surrounding dirt Pileup at high radius and low E Fit dirt-enhanced sample to extract dirt event rate with 10% uncertainty

  30. MiniBooNE motivation • The experiment • Oscillations • Analysis • Results • Summary and outlook

  31. nm ne Appearance Data! Joe Grange Miami 2011 December 2011 • Surprise! • Neither perfect agreement with background nor LSND-like signal!

  32. nm ne Appearance Data! Joe Grange Miami 2011 December 2011 • Below 475 MeV • Excess is 128 ± 20 (stat) ± 39 (syst) events (3σ excess) • Shape inconsistent with 2ν oscillation interpretation of LSND

  33. nm ne Appearance Data! Joe Grange Miami 2011 December 2011 • Above 475 MeV • Excellent agreement with background predictions • Region of highest sensitivity to an LSND-like 2ν mixing hypothesis, use it to exclude that model assuming CP conservation • Observe 408 events, expect 386 ± 20 (stat) ± 30 (syst)

  34. nm ne Appearance Data! Joe Grange Miami 2011 December 2011 • Neutrino-mode appearance analysis excludes LSND-like oscillations at 90% CL

  35. Low E Next Step: MicroBooNE Joe Grange Miami 2011 December 2011 • Low E excess either unexpected background or new physics - must be explained! Ambiguous between e, g-like events • MicroBooNE: next-generation liquid argon TPC with excellent e/g resolution • Construction expected soon e g

  36. Updates to Anti-Neutrino Analysis: Flux Revisited Joe Grange Miami 2011 December 2011 • Significant neutrino content in anti-neutrino beam • Detector not magnetized; cannot separate contribution based on m charge Phys. Rev. D 79, 072002 (2009)

  37. Updates to Anti-Neutrino Analysis: Flux Revisited Joe Grange Miami 2011 December 2011 • First measurement of neutrino contribution to anti-neutrino beam with non-magnetized detector • 3 independent, complementary measurements • m+/m- angular distribution • p- capture • m- capture Phys. Rev. D81: 072005 (2011) • Demonstration of techniques for other non-magnetized detectors looking for CP • NOnA, T2K, LBNE, etc.

  38. SciBooNE Joe Grange Miami 2011 December 2011 • SciBooNE: a fine-grained tracking detector 50m downstream of proton target in same n beam • SciBooNE provides powerful check of upstream beam content

  39. Updates to Anti-Neutrino Analysis: Flux Revisited Joe Grange Miami 2011 December 2011 • Tracking power of SciBooNE allows sensitivity to n parent rates through track multiplicity Phys. Rev. D84: 012009 (2011) • More visible tracks -> higher energy n’s • one track: mostly m-only • two: m + hadron • three: m + 2 hadrons • Extracted K+ rate: 0.85 ± 0.11 • applied to MiniBooNE n analysis

  40. nm ne Appearance Data! Joe Grange Miami 2011 December 2011 • Below 475 MeV • 38.6 ± 18.6 excess events • Entire energy region • 57.7 ± 28.5 excess events

  41. nm ne Appearance Data! Joe Grange Miami 2011 December 2011 • Data favors 2n oscillation fit over null hypothesis at 91.1% CL • (Fit above 475 MeV)

  42. 2010 neAppearance (5.66e20 POT) > 3 neutrinos not excluded from 2010 cosmology analyses Joe Grange Miami 2011 December 2011 • “LSND is right?!?” • En< 475 MeV: • 1.3s excess (by counting) • En > 475 MeV: • 1.5s excess (by counting) • Fit to 2nosc. prefers BF over null at 99.4% • Fluctuations happen! • ambiguous which direction which data set fluctuated, of course Phys. Rev. Lett. 105: 1818001 (2010)

  43. Both (Current) Data Sets Joe Grange Miami 2011 December 2011 ne, ne appearance comparison • combined ne, ne analysis underway • (CP violating model)

  44. Both Data Sets Joe Grange Miami 2011 December 2011 • Model independent comparison to LSND: L/E LSND MiniBooNE

  45. Joint MiniBooNE-SciBooNEnm Disappearance Analysis Joe Grange Miami 2011 December 2011 • By comparing rate and shape information in nm CC interactions between the two detectors, set limits for nm disappearance • world’s strongest limit at 10 < Dm2 (eV2) < 30 • Constrains nmne oscillations as well as other, more exotic models • extra dimensions, CPT • Forthcoming nm disappearance analysis arxiv: 1106.5685

  46. Joint MiniBooNE-SciBooNEnm Disappearance Analysis Joe Grange Miami 2011 December 2011 • Common n beam and n nuclear target, so many systematic errors cancel! Majority of remaining is MiniBooNE detector error • New BooNE proposal: MiniBooNE-like near detector for more sensitive osc. measurements (LOI: 0910.2698)

  47. “BooNE” Joe Grange Miami 2011 December 2011 • sensitivity with 1yr running at L = 200m (current MB L ~540m) • neappearance • nm disappearance (LOI: 0910.2698)

  48. MiniBooNE motivation • The experiment • Oscillations • Analysis • Results • Summary and outlook

  49. Conclusions Joe Grange Miami 2011 December 2011 • ne appearance analysis exposes unexpected low energy excess mostly incompatible with oscillations • MicroBooNE to test details soon • ne appearance data is consistent with LSND, but will need more data to definitively discriminate • more data on the way, but becoming dominated by syst. errors • “BooNE” near detector would help immensely • Simultaneous ne, ne fit to CP violating model underway • Joint MiniBooNE-SciBooNEnm disappearance results sets strong limits • corresponding nm analysis underway

  50. Thanks! Joe Grange Miami 2011 December 2011 Thanks for your attention!

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