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Main Slides

Main Slides. Signal region. Isotropic region. Low angle events. p. n e. N. 42 o. n. e +. 25-45 o. μ , π. n. reconstructed angle near 90 o. n (invisible). MC (decay electron channel not shown). SK-I/III combined final data sample. signal region. isotropic region (NC elastic).

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Main Slides

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  1. Main Slides

  2. Signal region Isotropic region Low angle events p ne N 42o n e+ 25-45o μ, π n reconstructed angle near 90o n (invisible) MC (decay electron channel not shown) SK-I/III combined final data sample signal region isotropic region (NC elastic) signal region isotropic region (NC elastic) low region (μ/π) low region (μ/π) νe CC μ/π NC elastic Cherenkov angle distribution degrees

  3. data νμ CC νe CC NC elastic μ/π > C. thr. all background relic SK-I/III E (MeV) 20-38 degrees 38-50 degrees 78-90 degrees

  4. Combined Fit SK-I/II/III combined likelihood logLikelihood combined 90% c.l. ev/yr interacting in 22.5 ktons combined 90% c.l.: < 5.1 ev / yr / 22.5 ktons interacting < 2.7 /cm2/s (>16 MeV) < 1.9 /cm2/s (scaled to >18 MeV)

  5. Secondary Slides

  6. Final Backgrounds (after all relic cuts) CC Backgrounds invisible μ decay e νe CC μ > C. threshold νμ CC νe CC μ/π NC elastic μ/π NC Backgrounds: Single π-, π+ > 200 MeV (~30%) Elastic (~39%) Single π+ < 200 MeV (~11%) Single π0’s (~11%) Multiple π production (~8%) other (<1%, neglect) These 3 can be modeled as a combination of other backgrounds, and thus aren’t considered separately E (MeV)

  7. Combined Fit SK-I/II/III combined likelihood logLikelihood combined 90% c.l. SK-I (~1500 days) SK-II (~790 days) SK-III (~550 days) combined ev/yr interacting in 22.5 ktons combined 90% c.l.: = 5.1 ev / yr / 22.5 ktons interacting = 2.7 /cm2/s (>16 MeV) = 1.9 /cm2/s (scaled to >18 MeV)

  8. SK-I data νμ CC νe CC NC elastic μ/π > C. thr. all background relic SK-I best fit is negative fit shown is 0 relic contribution SK-I only 90% c.l. limit: < 2.4 /cm2/s (>16 MeV) < 1.6 /cm2/s (scaled to >18 MeV) E (MeV) 20-38 degrees 38-50 degrees 78-90 degrees

  9. SK-II data νμ CC νe CC NC elastic μ/π > C. thr. all background relic Best fit (shown): 3.5 ev/yr interacting SK-II only 90% c.l. limit: < 7.4 /cm2/s (>16 MeV) < 5.2 /cm2/s (scaled to >18 MeV) E (MeV) 20-38 degrees 78-90 degrees 38-50 degrees

  10. SK-III data νμ CC νe CC NC elastic μ/π > C. thr. all background relic Best fit (shown) : 6.5 ev/yr interacting SK-III only 90% c.l. limit: < 8.1 /cm2/s (>16 MeV) < 5.7 /cm2/s (scaled to >18 MeV) E (MeV) 20-38 degrees 38-50 degrees 78-90 degrees

  11. Systematics: Inefficiency σineff SK-I: 3.5% SK-II: 4.5% SK-III: 3.1% • Define: • r = # relic events we see in data • R = # relic events actually occurring in detector • ε = efficiency (SK-I/II/III dependent) • assume ε follows a probability distribution P(ε) • assume P(ε) is shaped like Gaussian w/ width σineff • then we alter likelihood: then the 90% c.l. limit R90 is such that

  12. Cuts: efficiencies and sys errors • SK-III 96% (0.3%) 94% (0.3%) 98% (0.5%) 89% (1%) >99% • 99% (0.3%) 99% (2%) 69% 77% SK-I: effwall : 98% (0.5%) C. angle: 95% (0.4%) pion like: 98% (0.2%) spall+solar: 88% (1%) 2-peak, 2-ring: >99% Correlation cut: 99% (0.3%) 1st reduction: 99% (2%) (includes: electronic noise cuts, 50 us cut) Total: 78 % SK-II 95% (0.3%) 88% (0.3%) 97% (0.5%) 87% (1.4%) >99% 99% (0.3%) 99% (2%)

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