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Three Active Neutrino & Mass Degeneration Scenario

Presenting the search for appearance of electron neutrinos in neutrino beam experiments, focusing on mass degeneration scenarios with specific limits on mixing angles. Details on background rejection methods for pure neutrino detection are discussed. Sensitivity comparisons with other projects and expected outcomes are also highlighted.

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Three Active Neutrino & Mass Degeneration Scenario

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  1. JHF-SK neutrino workshop ne appearance search Yoshihisa OBAYASHI (KEK - IPNS)

  2. nm to ne oscillation search • Three Active Neutrino & Mass Degeneration Scenario : Dm212<<Dm213~Dm223 • Present Limit: sin22q13<10-1@Dm2~3x10-3eV2 • Obtained by CHOOZ (PALO VERDE) experiment • Neutrino Beam is Essentially Pure nm • (nm : ne~100:0.2@peak) • ne appearance search = small q13 search ~0.5 from SK Atm. n JHF-SK neutrino workshop @ KEK

  3. Appearance Signal • ne C.C. interaction • Single Fussy Ring • Cherenkov Angle ~ 42o ne e+- shower JHF-SK neutrino workshop @ KEK

  4. BG(1): nm C.C. interaction • Sharp Ring Edge • Cherenkov Angle < 42o • easy to reject nm m JHF-SK neutrino workshop @ KEK

  5. BG(2): N.C. p0 production • p0→2g : 2 Shower Rings • 2 rings overlap • A ring is too weak • Not Reproduce En Single Ring n n p0→2g 2 showers JHF-SK neutrino workshop @ KEK

  6. p0 production • Sudden raise from En~500MeV s(w/p0)/s(total) En(GeV) JHF-SK neutrino workshop @ KEK

  7. ne selection • SK Atmn official selection (single-ring e-like): • Fully Contained (No Anti-counter Activity) • Only one ring is reconstructed • PID likelihood is e-like (Showering) • No Muon Decay Electron • Evis > 100MeV Dm2=3x10-3eV2, sin22qme=0.05 Too Much! JHF-SK neutrino workshop @ KEK

  8. Tight e/p0 separation • p0 BG tend to have a forward peak • cosqne: Large for BG • 2nd ring for the signal is fake • E(g2)/E(g1+g2): Large for BG • Likelihood diff. between 1-ring and 2-rings • Invariant mass JHF-SK neutrino workshop @ KEK

  9. e/p0 separation efficiency Dm2=3x10-3eV2, sin22qme=0.05 JHF-SK neutrino workshop @ KEK

  10. p0 contamination • Black: Single-ring e-like ~2% • Green: Standard p0 rejection ~0.2% • Red: More tight p0 rejection ~0.1% Eff. Identified as ne En(GeV) JHF-SK neutrino workshop @ KEK

  11. BG(3): nt C.C. • nmnt+N t e could be a source of BG • Energy threshold > 3 GeV • Negligibly small JHF-SK neutrino workshop @ KEK

  12. Expected Signal & BG distribution • Reconstruct En as Quasi-Elastic interaction • Apply Energy Cut • 0.4GeV< E <1.2GeV (OAB2o) OAB2o 5year JHF-SK neutrino workshop @ KEK

  13. Sensitivity for Mixing Angle sin22qme sensitivity JHF-SK neutrino workshop @ KEK

  14. Sensitivities • Sensitive down to sin22qme>3x10-3@Dm2=3x10-3eV2 • By tuning En, sensitive down to sin22qme>5x10-3 in all allowed Dm2atm • sin22q13>1x10-2 JHF-SK neutrino workshop @ KEK

  15. Sensitivities (2) JHF-SK neutrino workshop @ KEK

  16. Comparison to Other Projects • MINOS: • Too high En • ntCC→t→e may be a serious BG • OPERA(,ICARUS) • Target physics is different (nt app.) • Much more high En • Small Far Detector JHF-SK neutrino workshop @ KEK

  17. Summary • ~1 GeV neutrino beam + SK(Water Cherenkov) seems to be a best solution to search: 0.01 < sin22q13 < 0.1 @ Dm2atm. • Expected sensitivity: sin22q13~ 0.01 @ 90%C.L. • JHFnu-SK has much higher sensitivity for ne appearancesearch than MINOS and OPERA. JHF-SK neutrino workshop @ KEK

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