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JHF neutrino ( n e appearance)

This article provides information on the JHF Neutrino Experiment, a project to explore neutrino oscillations. It discusses the different options for the neutrino beam, the physics goals, and the potential for discovering new neutrino properties.

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JHF neutrino ( n e appearance)

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  1. JHF neutrino(ne appearance) Yoshihisa OBAYASHI ICRR, Univ. of Tokyo

  2. JHF n Working Group Y. Itow, Y. Obayashi, Y. Totsuka (ICRR) Y. Hayato, H. Ishino, T. Kobayashi, K. Nakamura, M. Sakuda (KEK) T. Hara (Kobe) T. Nakaya, K. Nishikawa (Kyoto) T. Hasegawa, K. Ishihara, A. Suzuki (Tohoku) A. Konaka (TRIUMF)

  3. N 50GeV PS 3GeV PS Neutrino Beam Line 600MeV Linac FD To SK JHF neutrino beam JAERI @ Tokai-mura Construction: 2001 ~ 2006 1021p.o.t./1year(130day)

  4. Far Detector Super-Kamiokande @Kamioka (295km from JAERI) • 50,000t Pure Water as Target • 22.5kt Fiducial Volume • Energy measurement by total amount of Cherenkov light • e-m separation is done by ring pattern likelihood

  5. Neutrino Beam at JHF (Conventional) • Three Possible options: • Wide Band Beam (WBB) 2 horns, almost same as K2K • Narrow Band Beam (NBB) Horn(s) + Bending • Off Axis Beam Another option of NBB

  6. Wide Band Beam • Advantage • High Intensity • Wide sensitivity in Dm2 • Established technique • Disadvantage • Back Grounds from HE tail • Spectra diff. btw near&far • Systematic error • Needs Heavy shielding • decay pipe must be short ~ 4200 nm int./22.5kt/yr (ne:0.8%)

  7. Narrow Band Beam • Advantage • Less systematic error • Less BG from HE tail • Easy to tune En • Less shielding • Disadvantage • Low intensity ~ 830 nm int./22.5kt/yr (ne:0.3%@peak)

  8. q Off Axis Beam • Another option of NBB ref:BNL-E889 Proposal • WBB with intentionally misaligned from detector axis • Quasi Monochromatic Beam

  9. Off Axis Beam • Advantage • More intense than NBB • Disadvantage • More HE tail than NBB • Hard to tune En • Needs Heavy shielding • Not established technique • Beam monitor • Near/Far ratio, … ~ 2200 nm int./22.5kt/yr (ne:0.2%@peak)

  10. nm→nx disappearance: Precise measurement of oscillation parameters: d(Dm232)~ 2x10-4eV2, d(sin22qmx)~ 1% nm→ne appearance: Explore down to sin22qme ~ 3x10-3 (= sin22q13・sin2q23) 3flavor oscillation: Dm12<<Dm23~Dm13 Physics Goal of JHF to SK P=sin22q・sin2(1.27Dm232L/En) Dm232=2~5x10-3eV2, L=295km Osc. Max @ En=0.5~1.2GeV

  11. nm disappearance • Fit with 1-sin22q・sin2(1.27Dm2L/E) • Ratio after BG subtraction:

  12. nm disappearance • Possible systematic errors: • inelastic cross section: 20% • Spectrum @FD: 4%・E • Spectrum diff.(Near/Far): 10% • Energy measurement: 3% • d(sin22q)~0.01 in 5 years

  13. nm → ne appearance • P= sin22qme ・ sin2(1.27Dm2L/E) • Goal: sin22qme ~ 3x10-3 • Present limit: ~ 5x10-2 • sin22qme= sin22q13・ sin2q23 <0.1, ~0.5 CHOOZ

  14. Signal & Backgrounds Signal: ne C.C. interaction • Single fuzzy ring • Cherenkov angle ~ 42deg. ne e+- shower BG 1: nm C.C. interaction • Sharp ring edge • Cherenkov angle < 42deg. nm m • easy to reject

  15. Backgrounds (continued) BG 2: N.C. p0 production n n 2 showers p0→2g • 2 fuzzy rings → hard to separate • Not reproduce En • need effort to reject

  16. ne selection by SK official cuts • S/N ~ 1/3 (@sin22qme=0.05) • Main Background come from p0 sin22qme=0.05, Dm2=3x10-3eV2

  17. Force to find 2ndg ring Cut with follow quantities: Shower direction w.r.t. n (cosqne) Energy fraction of 2ndg R(g2)=E(g2)/(E(g1)+E(g2)) Pattern likelihood difference Invariant mass of 2 g p0 rejection

  18. p0 cut efficiency PRELIMINARY WBB 1year NBB 1year Off Axis 1year

  19. Oscillation sensitivity • sin22qme~5(3)x10-3 @90%CL by 5year run of NBB (off axis beam) PRELIMINARY 10% systematic in BG rate is considered

  20. Oscillation sensitivity PRELIMINARY 10% systematic in BG rate is considered

  21. Summary • JHF neutrino experiment • Expected to start in 2006 • Far Detector: Super-K • By 5 years of run: • nm disappearance search • d(Dm2) ~ 2x10-4eV2 • d(sin22q) ~ 1% • ne appearance search • sin22qme ~ 5x10-3 @90%CL by 5year run • nm⇔nt or nm⇔nsterile • Can be tested

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