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MiniBooNE Low Energy Analysis

MiniBooNE Low Energy Analysis. H. Ray Los Alamos National Laboratory. Oscillation Fit Reporting. The final fit for     e oscillations was performed using 2 different analyses Track Based : E  QE 475 MeV to 3 GeV Boosting : E  QE 300 MeV to 3 GeV

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MiniBooNE Low Energy Analysis

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  1. MiniBooNE Low Energy Analysis H. Ray Los Alamos National Laboratory

  2. Oscillation Fit Reporting • The final fit for  e oscillations was performed using 2 different analyses • Track Based : EQE475 MeV to 3 GeV • Boosting : EQE 300 MeV to 3 GeV • Increased from 300 MeV due to 2 fit of 1% in Evis variable during 1st step of unblinding process H. Ray

  3. Oscillation Fit Reporting • We felt that we had checked everything to our full ability, and to our best knowledge could not further constrain processes in the low E region • MC studies of potential LSND oscillation signals indicated we could tighten the E requirement with a negligible loss in sensitivity • Prior to unblinding, we agreed to also examine events with EQE > 300 MeV in the Track Based analysis H. Ray

  4. Observed Event Distribution H. Ray

  5. Observed Event Distribution Background-subtracted 475 MeV to 3 GeV Counting Expt : 300 MeV < EQE< 1.250 GeV 749 observed evts 631 ± 25 ± 45 expected events Excess over background : 2.3 H. Ray

  6. Counting Expt : 300 MeV < EQE< 475 MeV Excess over background : 3.7 Observed Event Distribution Background-subtracted 475 MeV to 3 GeV H. Ray

  7. Excluded by Bugey! Observed Event Distribution Background-subtracted 300 MeV to 3 GeV Best Fit (sin22, m2) = (1.0, 0.03 eV2) 2 Probability: 18%, Null Hypothesis= 3% Only 4% Compatible w/LSND H. Ray

  8. What are the Low-E Events? • These low Energy events could be many things • We saw these events for the first time on Monday, March 26th (2007) • The following presents our very preliminary investigations to date H. Ray

  9. Fit Energy Event Composition intrinsic e  mis-id • Boost Analysis • 300 MeV to 3 GeV • Likelihood Analysis • 475 MeV to 3 GeV H. Ray

  10. Low Energy Event Composition intrinsic e  mis-id • Boost Analysis • 300 MeV to 475 MeV • Likelihood Analysis • 300 MeV to 475 MeV H. Ray

  11. Fundamental Information Low E events show no bias in event time Not normalized to POT 369 events 369 events Shutdowns H. Ray

  12. Cosmic Rays Measured from our strobe data Low E events show no bias in Y (vertical) position Cosmic events populate upper region of tank 369 events H. Ray 2 expected evts in osc. analysis

  13. Radiative Delta and NC0 • Constrain our NC0 production rate using data from our detector • Reduces error on mis-id 0 (<2%!) • This also constrains the radiative  resonance rate, thus constraining rate of  N  H. Ray

  14. What we know so far • Low E events pass EM Particle ID • Gamma or electron • The evts do not appear to be biased in run range or event time • The evts do not appear to be due to cosmic ray background • Radiative Delta : unlikely = need x3 increase • NC0 : unlikely = measure very well with our data H. Ray

  15. Summary • A two-neutrino appearance only model systematically disagrees with the shape of the excess as a function of E • Need to investigate non-oscillation explanations of the low E excess • Investigation of these low E events is underway H. Ray

  16. Final Results • Any conclusions drawn about the low E events will have no effect on our oscillation result H. Ray

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