1 / 30

Recent Results from Super-Kamiokande on Atmospheric Neutrino Measurements

Recent Results from Super-Kamiokande on Atmospheric Neutrino Measurements. Choji Saji ICRR,Univ. of Tokyo for the Super-Kamiokande collaboration. ICHEP 2004, Beijing. Contents. Atmospheric neutrino oscillation studies using full Super-Kamiokande I(SK-I) data

tehya
Télécharger la présentation

Recent Results from Super-Kamiokande on Atmospheric Neutrino Measurements

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Recent Results from Super-Kamiokande on Atmospheric Neutrino Measurements Choji SajiICRR,Univ. of Tokyofor the Super-Kamiokande collaboration ICHEP 2004, Beijing Contents • Atmospheric neutrino oscillation studies using full Super-Kamiokande I(SK-I) data • nm  nt oscillation analysis • L/E analysis • 3-flavor analysis • StatusofSuper-Kamiokande II(SK-II)

  2. Zenith angle p, He … , K  Flux(m-2sec-1sr-1GeV-1)   Zenith angle dist. of Atmospheric n flux Atmospheric neutrinos  Downward （L=10~100 km） e± e Upward （L=up to 13000 km） cosq En > a few GeV Up/Down Symmetry

  3. Event classification n energy distribution Fully Contained (E ~1GeV) Partially Contained (E ~10GeV) Stopping (E~10GeV) Through-going (E~100GeV) Atmospheric neutrinos in Super-Kamiokande

  4. 2-flavor oscillation analysis Data set: full SK-I (FC,PC 1489days, up- 1646 days) Improvements: • Expectation - Three dimensional (3D) n flux calculation -  interaction parameters (tuned by K2K data) • Treatment of systematic errors in c2 calculation • Each systematic error source is treated as independent error term(39 error terms)

  5. Zenith angle distributions    2-flavor oscillations Best fitsin22q=1.0, Dm2=2.1x10-3 eV2 Null oscillation ~13000km ~500km ~15km ~13000km ~500km

  6.  2-flavor oscillations Oscillation Analysis Results (FC + PC + UP-m) 10-3 10-2 • Best fit: sin22 =1.0 m2 = 2.1x10-3 eV2 2 = 175.2/177 dof • 90% C.L. region: sin22 > 0.92 1.5 < m2 < 3.4x10-3 eV2 0.7 0.75 0.8 0.85 0.9 0.95 1 Full paper will be soon

  7. Oscillation Decay Decoherence L/E Analysis A first dip should be observed • Direct evidence for oscillations • Strong constraint to oscillation parameters, especially Dm2 value FC single-ring 1/2 oscillation Full oscillation • Expand fiducial volume(FC) • need more statistics • Select events with highresolution in L/E • DL/E < 70% • FC(single, multi-ring) m-like • PC D(L/E)=70%

  8. L/E Distribution Mostly upward 1489.2 days FC+PC Best fit expectation w/ systematic errors Null oscillation MC Mostly downward First dip is seen as expected by neutrino oscillation

  9. Oscillation Decay Decoherence L/E Significance Dc2 (n decay –n oscillation) =11.4 3.4 s Dc2 (n decoherence -n oscillation)=14.6 3.8 s The first dip of the data cannot be explained by other models

  10. standard zenith angle analysis(90%C.L.) L/E Oscillation result Dm2=2.4x10-3,sin22q=1.00 c2min=37.9/40 d.o.f (sin22q=1.02, c2min=37.7/40 d.o.f) 1.9x10-3 < Dm2 < 3.0x10-3 eV2 0.90 < sin22q@ 90% C.L. Strong constraint on Dm2

  11. m3 Dm223 m2 Dm212 m1 3-flavor Oscillation assuming Dm212 = 0　eV2 neutrino oscillation probabilities are described as; P(negnm) = sin2(2q13) x sin2q23 x sin2(1.27Dm2L/E) P(nmgnt) = cos4q13 x sin2(2q23) x sin2(1.27Dm2L/E) P(negne) = 1 - sin2(2q13)x sin2(1.27Dm2L/E) 3 parameters; Dm223= Dm213, q13, q23 Oscillation probability ( cosQ=-0.6) P(nene) matter effect log10(E(GeV))

  12. Dm2 sin2q13 3-Flavor Analysis result (preliminary) sin2q13 Dm2 m3 normal m2 m1 m2 m1 sin2q13 inverted m3 Bestfit: Dm2 = 2.7x10-3ev2, sin2q23 = 0.5, sin2q13 = 0.0 sin2q23 no evidence for non zero q13

  13. SK - II

  14. Status of SK-II Atmospheric Neutrinos Preliminary! SK-II event • 311.5days data (preliminary) • SK-II data are consistent with SK-I • Clear deficit in upward nm

  15. Conclusion SK-I analysis  oscillation • SK-I full data set (FC,PC 1489days, up- 1646days) • Improved MC prediction and oscillation analysis •  allowed region @ 90% C.L. 1.5 < m2 < 3.4x10-3 eV2, sin22 > 0.92 • SK-I final result will be published soon L/E analysis • Evidence for oscillatory signature1.9 < Dm2 < 3.0x10-3 eV2, sin22q > 0.90@90%C.L. 3 - flavor oscillation - no evidence for non zero q13 SK-II analysis is in progress -preliminary data are consistent with SK-I

  16. Supplements

  17. CPT VIOLATION

  18. 2-flavor

  19. Definition of 2 2-flavor Calculation methods, basic idea (based on Fogli et al., hep-ph/0206162) In our current analysis, minimum χ2 is obtained by optimizing εj (j = 1,2,..) for each (sin22θ,Δm2) point. But, mathematically, χ2 is minimum ⇔ for any j . Minimizing χ2 ⇔ Solving nsys linear equation.

  20. Sub-Sample Consistency 2-flavor Check oscillation fit using different samples of data independently each allowed region overlaps with best fit point

  21. L/E Reconstruction of E and L Neutrino energy Neutrino direction FC single-ring En Preliminary Eobserved Eobserved  En Zenith angle  Flight length Neutrino energy is reconstructed from observed energy using relations based on MC simulation Neutrino flight length is estimated from zenith angle of particle direction

  22. L/E Event samples in L/E analysis 1.5m from top & bottom FC single-ring, multi-ring m-like 22.5kt →26.4kt Expand fiducial volume 1m from barrel More statistics for high energy muons observed charge / expectation from through-going PC Classify PC events using OD charge OD stopping OD through-going • OD stopping • OD through going OD through-going MC Different L/E resolution OD stopping MC

  23. Sensitivities to alternative models n decoherence obtained Dc2 Consistent with the expectation n decay Assumption nm nt 2 flavor oscillation (Dm2=2.0x10-3eV2,sin22q=1.0) L/E resolution cut at 70%

  24. L/E Definition of c2 Poisson with systematic errors Nobs : observed number of events Nexp : expectation from MC ei : systematic error term si: sigma of systematic error Various systematic effects in detector, flux calculation and neutrino interaction are taken into account

  25. 3-flavor Real Dm2 =positive assumed P(nmne) cosQ En(GeV) (No resonance for anti-neutrinos)

  26. c2 definition for 3-flavor analysis analytic calculation of Mij x ej = vi

  27. CC ne CC ne 3-flavor Single-ring e-like Multi-ring e-like NC + Others NC +Others CC ne CC ne

  28. 20inch PMT with Acrylic + FRP vessel SK-II SK-II partially-contained sample • Rebuilt in summer 2002 • Has 47% of original ID 20inch PMTs (~5200) • 20inch PMTs in acrylic shells to prevent future chain implosions • Has full OD 8inch PMTs (1885) • Started data taking inDec. 2002

  29. SK2 Number of Events / Event rate in fiducial volume Number of Events (Event rate, Ev/day)

More Related