Conventional Neutrino Beam Experiment : JHF – Super-Kamiokande Yoshihisa OBAYASHI (Kamioka Observatory, ICRR) Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

JHF Neutrino 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) Konaka (TRIUMF) http://neutrino.kek.jp/jhfnu Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

Overview of JHF – SK nm→nx disappearance: nm→ne appearance: Precise measurement of oscillation parameters: d(Dm232)~ 2x10-4eV2, d(sin22qmx)~ 1% nm→ne appearance: Explore down to sin22qme ~ 5x10-3 Oscillation Max @ En=0.5~1.2GeV P=sin22q・sin2(1.27Dm232L/En) Dm232=2~5x10-3eV2, L=295km Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

JHF (Japan Hadrons Facility) JAERI @ Tokai-mura Construction: 2001 ~ 2006 N 50GeV PS 3GeV PS Neutrino Beam Line 600MeV Linac Front Detector(s) To Super-Kamiokande J H F MINOS K 2 K E(GeV) 50 120 12 Int.(1012ppp) 330 40 6 Rate(Hz) 0.29 0.53 0.45 Power(MW) 0.77 0.41 0.0052 1021p.o.t./1year(130day) Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

Far Detector Super-Kamiokande @ Kamioka Operation Start: 1996 295 km from JAERI 50.0kt Pure Water in the tank 22.5kt Fiducial Volume as a neutrino target Energy measurement by total amount of Cherenkov light e-m separation is performed by ring pattern likelihood Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

Neutrino Beam at JHF Three Possible options: Present Strategy: Wide Band Beam (WBB) 2 horns, almost same as K2K Narrow Band Beam (NBB) Horn(s) + Bending Off Axis Beam Another option of NBB Present Strategy: First 1(~2) year: High Statistics Run with WBB Pin down Dm2 Next 5 years: Precise Analysis with (one of) NBB Measurement of q23,q13 Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

Wide Band Beam High Intensity Wide sensitivity in Dm2 Established technique Backgrounds 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%) Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

Narrow Band Beam Less systematic error Less BG from HE tail Easy to tune En Less shielding Low intensity ~ 830 nm int./22.5kt/yr (ne:0.3%@peak) Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

Off Axis Beam: Another option of NBB q WBB with intentionally misaligned from detector axis Quasi Monochromatic Beam Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

Off Axis Beam More intense than NBB 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) Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

Physics Sensitivity Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

nm Disappearance Ratio after BG subtraction: Fit with 1-sin22q・sin2(1.27Dm2L/E) Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

nm Disappearance d(sin22q)~0.01 in 5 years 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 Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

nm → ne Appearance Three flavor oscillation framework: Dm212 <<Dm223 ~Dm213≡Dm2 Dm223= Dm2atm>10-3eV2 Dm212= Dm2sol<10-4eV2 Oscillation Probability P : Present limit: sin22qme > 5x10-2 sin22qme= sin22q13・ sin2q23 sin22q13 <0.1(CHOOZ) sin2q23 ~ 0.5 (Atmospheric n) Goal: sin22qme ~ 5x10-3 m22 m12 m32 Dm2atm Dm2sol Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

ne nm m easy to reject Signal & Backgrounds Signal: ne C.C. interaction BG 1: nm C.C. interaction Single fuzzy ring Cherenkov angle ~ 42deg. ne e+- shower Sharp ring edge Cherenkov angle < 42deg. nm m easy to reject Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

Backgrounds (continued) BG 2: N.C. p0 production n n p0→2g 2 showers 2 fuzzy rings → hard to separate Not reproduce En need effort to reject Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

ne Selection by SK Official Cuts nm (w/p0) ne Fid. Vol. 3651 795 53.3 1R e-like 92 68 29.5 reduct.rate 2.5% 8.6% 1.8% sin22qme=0.05, Dm2=3x10-3eV2 S/N ~ 1/3 (@sin22qme=0.05) Main Background come from p0 Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

p0 rejection Force to find 2nd g ring Cut with follow quantities: Shower direction w.r.t. n (cosqne) Energy fraction of second g R(g2)=E(g2)/(E(g1)+E(g2)) Pattern likelihood difference Invariant mass of 2 g Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

p0 cut efficiency PRELIMINARY WBB 1year NBB 1year Off Axis 1year WIDE nm ne Fid. Vol. 3651 53.3 1R e-like 92(2.5%) 29.5(55.3%) p0 cut 4.0(0.1%) 9.8(18.4%) NBB 1year LE2p nm ne Fid. Vol. 740 23.0 1R e-like 13.2(1.8%) 16.2(70.4%) p0 cut 1.8(0.2%) 11.6(50.4%) Off Axis 1year 2deg. nm ne Fid. Vol. 1801 45.5 1R e-like 37.4(2.1%) 32.1(70.5%) p0 cut 3.8(0.2%) 24.3(53.4%) sin22qme=0.05, Dm2=3x10-3eV2 Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

nm → ne Oscillation Sensitivity PRELIMINARY 10% systematic in BG rate is considered sin22qme~5(3)x10-3 @90%CL by 5year run of NBB (off axis beam) Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

nm → ne Oscillation Sensitivity PRELIMINARY 10% systematic in BG rate is considered Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

Comparison to MINOS MINOS Ph2he,me,le 2yr exposure (hep-ph0005012) JHF neutrino is more sensitive especially in Atmospheric Dm2 region Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

nm→ nt? nsterile? nm nt nsterile nt ⇔ nsterile discrimination NC p0 production: n + N → n + N + p0 In the case of nm→ nsterile oscillation, Number of p0 also decrease nt ⇔ nsterile discrimination CC NC nm Yes nt Few nsterile No Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

nm disappearance search 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 nm⇔nt or nm⇔nsterile Can be tested Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000

Test of CP Violation If sin22q13 ~ 0.01: 1MW(2deg. off axis) → SK : 2 nm → ne / year Too few to see CP 4MW → Mton : 300 nm → ne / year 100 nm → ne / year 1year n + 3year n 600 total events with asym: 150xsind d=30deg.(3s), 12deg.(90% CL) Yoshihisa OBAYASHI, Honolulu- Oct. 6, 2000