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スーパーカミオカンデ１１４０日の 大気ニュートリノ観測

日本物理学会＠新潟大 2000. Sep. 22. スーパーカミオカンデ１１４０日の 大気ニュートリノ観測. n m → n t 　２ 世代解析 n m -n t -n e 　３世代解析 n n 　ratio の測定. 大林　由尚　（東京大学宇宙線研究所） 他　 Super-Kamiokande　Collaboration. Event Categories. Fully Contained (FC) n m CC, n e CC, NC <E n >~1GeV Partially Contained (PC) n m CC

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スーパーカミオカンデ１１４０日の 大気ニュートリノ観測

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  1. 日本物理学会＠新潟大 2000. Sep. 22 スーパーカミオカンデ１１４０日の大気ニュートリノ観測 nm → nt　２世代解析 nm-nt-ne　３世代解析 n n　ratio の測定 大林　由尚　（東京大学宇宙線研究所） 他　Super-Kamiokande　Collaboration

  2. Event Categories • Fully Contained (FC) • nm CC, ne CC, NC • <En>~1GeV • Partially Contained (PC) • nm CC • <En>~10GeV • Upward Going Muon (Upm) • nm CC • <En>~10GeV (Stop m) ~100GeV (Through m)

  3. Sub-GeV (Evis<1.33GeV) Multi-GeV (Evis>1.33GeV) Observed Events (SK 1140day)

  4. ●DATA ーMC(w/o osc.) ーMC(w/ osc.) Zenith Angle • P(osc)= sin22q・sin2(1.27Dm2L/E) • U/D(Multi-GeV FC+PC)= 0.54±0.04±0.01

  5. 2 Flavor Oscillation Analysis (nm-nt) • Oscillation Analysis by FC + PC + Upmu • Best Fit: c2min=135.4/152d.o.f ＠ sin22q=1.00 Dm2=3.2x10-3eV2 • Assuming null osc.: c2min=316.2/154d.o.f • Allowed region @90%C.L.: 0.88<sin22q 1.5x10-3<Dm2<5x10-3 (eV2)

  6. Approximation: Dm223>> Dm212 Dm223= Dm2atm>10-3eV2 Dm212= Dm2sol<10-4eV2 Dm223~Dm213≡Dm2 Osc. Probability: Parameters: (sin2q13,sin2q23,Dm2) Matter effects considered as 5 step density function 3 Flavor Oscillation Analysis (nm-nt-ne) m32 Dm2atm m22 Dm2sol ( ) m12

  7. 3 Flavor Analysis Result • Data Set: FC + PC • Best Fit: (ê) sin2q13=0.019, sin2q23=0.55, Dm2=2.5x10-3eV2 • sin2q13<0.34 @90%CL • Consistent with pure　maximal nm→nt(Ñ) • Consistent with CHOOZ ê Ñ ê ê

  8. Measurement of nm- nm ratio • Motivation: • A test of the atmn flux prediction • In the case of nm+ N → m- X : • m- can be captured by nucleus • # decay electron ↓ • (m- life → short) • Data & MC are consistent within 1s

  9. Summary • Atmospheric Neutrino @ Super-Kamiokande • Livetime: 1140days • 2 flavor oscillation analysis: (@90%C.L.) • Mixing angle: sin22q>0.88, • Mass difference: Dm2=1.5~5x10-3eV2 • 3 flavor analysis: • sin2q13<0.34 (@90%C.L.) • consistent with pure nm→nt, CHOOZ • nm– nmratio: • Data & MC are consistent within 1s

  10. Transparencies for the Back Pocket

  11. Atmospheric Neutrino Production Flavor ratio

  12. Super-Kamiokande • 50.0kt Pure Water • 22.5kt Fid.Vol. • 1000m UnderGround (2700m.w.e.) • 11146 PMTs for ID • 1885 PMTs for OD • Operation started in Apr. 1996

  13. Oscillation Analysiswith 3D Flux Calculation Preliminary • Oscillation Analysis by FC + PC + Upmu • Best Fit: c2min=147.8/152d.o.f ＠ sin22q=1.00 Dm2=3.5x10-3eV2 • Incl. Unphys. Region: c2min=146.7/152d.o.f ＠ sin22q=1.05 Dm2=3.5x10-3eV2

  14. nt or nsterile? NC enrich #ring>1 e-like Evis>400MeV • nm→nsterile oscillation is disfavored at 99% C.L. High E PC Evis>5GeV Up thru m

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