Takaaki Kajita Takaaki Kajita ICRR and IPMU, Univ. of Tokyo ICRR and IPMU, Univ. of Tokyo
Outline • Introduction • Future possibilities of the J-PARC neutrino beam • Sensitivity studies • Some remarks • Summary This talk discusses several possibilities with the J-PARC neutrino beam in the future. The concrete plan for the future experiment after T2K phase-I is still to be decided. No discussion of oscillation probabilities. See theory talks for details of osci. prob..
������������� ������������� ν ν We know that � � ν = ⋅ ν � neutrinos have masses � � and mixing angles: ν ν � τ Various experiments Various experiments ν e ν � ν τ ν e ν � ν τ ν 3 ν 3 � m 23 Atmospheric Atmospheric 2 LBL LBL ν 2 ν 2 Solar Solar � m 12 2 ν 1 ν 1 KamLAND KamLAND
θ 13 θ θ θ θ θ θ θ experiments 13 experiments ��������� ��������� International International Falls Falls Duluth Duluth Minneapolis Minneapolis Fermilab Fermilab We assume that evidence for non-zero sin 2 2 θ 13 is observed by We assume that evidence for non-zero sin 2 2 θ 13 is observed by the present/near future experiments (sin 2 2 θ 13 > ~0.01). the present/near future experiments (sin 2 2 θ 13 > ~0.01). � We assume that we have strong motivation to the next stage. � We assume that we have strong motivation to the next stage.
θ 13 θ θ θ Beyond θ θ θ θ Beyond 13 If θ 23 ≠ π /4, If θ 23 ≠ π /4, θ 13 θ 13 Sign of � m 23 Sign of � m 23 2 2 is it > π /4 or < π /4 ? is it > π /4 or < π /4 ? ν e ν � ν τ ν 3 ν e ν � ν τ ν 3 ν 2 ν 1 or or ν 3 CP ? CP ? Can the J-PARC neutrino beam contribute to these measurements?
ν ν ν ν beam PARC ν ν ν ν Future possibilities of the J- -PARC beam Future possibilities of the J Slide by A.Suzuki, KEK Roadmap Review Committee, March 2008 Assumed in most part of this talk
Direction: J- -PARC neutrino beam PARC neutrino beam Direction: J (under water… Korea, Okinoshima Korea, Okinoshima 400 – 1000 km) Kamioka, 295km 1000 - 1250km Island, 660km Kamioka, 295km 1000 - 1250km Island, 660km But no discussion In this talk… Fig: Senda NP04 In this talk, various difficulties in each option are not considered.
Possible detector options… … Possible detector options Large Liq. Ar Large Liq. Ar Large water Cherenkov detector Large water Cherenkov detector detector detector (Hyper-Kamiokande) (Hyper-Kamiokande) 0.1 Mton fiducial mass. 0.1 Mton fiducial mass. 0.54 Mton fiducial mass (If the detector 0.54 Mton fiducial mass (If the detector is divided into 2, located at Kamioka is divided into 2, located at Kamioka and Korea, fiducial mass for each unit is and Korea, fiducial mass for each unit is 0.27Mton.) 0.27Mton.)
Oscillation probabilities Oscillation probabilities 2.5 degree Flux 1.0 degree L=295km L=1050km L=660km Normal hierarchy, δ =0 sin 2 2 θ 13 =0.05 Normal hierarchy, δ = π /4 Inverted hierarchy, δ =0 Inverted hierarchy, δ = π /4 Larger E (longer L) � larger matter effect � better for mass hierarchy Larger E (longer L) � larger matter effect � better for mass hierarchy 2 nd osci. maximum � large CP effect � systematic errors less important (?) 2 nd osci. maximum � large CP effect � systematic errors less important (?)
Expected sensitivity (some early results) Expected sensitivity (some early results) hep-ph/0504026 0.27 Mton fid. Mass at Kamioka and Korea (water Ch) 0.27 Mton fid. Mass at Kamioka and Korea (water Ch) 4 years ν beam + 4 years anti- ν beam, 4MW, 2.5 deg Off-axis 4 years ν beam + 4 years anti- ν beam, 4MW, 2.5 deg Off-axis CP violation (sin δ ≠ 0) CP violation (sin δ ≠ 0) Mass hierarchy Mass hierarchy -1� -1� 10� 10� normal� -2� -2� 10� 10� Kamioka 0.54 Mton� θ 13� θ 13� Kamioka 0.27 Mton + Korea 0.27 Mton� 2� normal� 2� 2� sin� 2� sin� 0 1 2 3 � 4 5 6� � 0 1 2 3 � 4 5 6� � -1� -1� 10� 10� inverted� -2� -2� 10� 10� 3 σ (thick) 2 σ (thin) 3 σ (thick) 2 σ (thin) inverted� 0 1 2 3 � 4 5 6� � 0 1 2 3 � 4 5 6� � δ δ
Signal and background in a water Signal and background in a water Cherenkov detector Cherenkov detector ν e signal ν e signal π 0 BG π 0 BG BG events need to be reduced: BG events need to be reduced: � Cut based analysis (used in the T2K sensitivity studies, I.Kato’s talk ) � Cut based analysis (used in the T2K sensitivity studies, I.Kato’s talk ) � Max. likelihood analysis ( needed to extend to higher � Max. likelihood analysis ( needed to extend to higher energies). energies).
Recent study (1) Recent study (1) (Kamioka only, water Cherenkov (Kamioka only, water Cherenkov detector) detector) K. Kaneyuki, NP08 Detailed MC study with the usual T2K cuts Detailed MC study with the usual T2K cuts Kamioka (L=295 km) 8 1.66 MW, 0.54 Mton, 2.2years of ν � beam, 7.8 years 1.66 MW, 0.54 Mton, 2.2years of ν � beam, 7.8 years E = 0.5 GeV (Normal) 7 of anti- ν � beam of anti- ν � beam E = 0.6 GeV (Normal) E = 0.7 GeV (Normal) 6 E = 0.8 GeV (Normal) P( ν µ ν e ) [%] E = 0.5 GeV (Inverted) 5 Normal hierarchy E = 0.6 GeV (Inverted) ��� � � θ �� ����� E = 0.7 GeV (Inverted) 4 E = 0.8 GeV (Inverted) 3 2 1 0 0 1 2 3 4 5 6 7 0 P( ν µ ν
CP violation sensitivity CP violation sensitivity (Kamioka only, water Cherenkov detector) (Kamioka only, water Cherenkov detector) K. Kaneyuki, NP08 Assumed systematic errors: Assumed systematic errors: � Signal efficiency ---- 5% � Signal efficiency ---- 5% � BG ---------------------- 5% � BG ---------------------- 5% 3 σ σ σ σ � Beam ν e BG ----------- 5% � Beam ν e BG ----------- 5% 2 σ σ σ σ � Neutrino / anti-neutrino � Neutrino / anti-neutrino 1 σ σ σ σ cross section ratio -- 5% cross section ratio -- 5% (Normal hierarchy assumed) (Normal hierarchy assumed) Kamioka (water Ch.) Kamioka (water Ch.) 3 σ detector can do a detector can do a reasonably good job to reasonably good job to demonstrate the CP demonstrate the CP violation (if sin 2 2 θ 13 > ~0.01, violation (if sin 2 2 θ 13 > ~0.01, and hierarchy known). and hierarchy known).
Recent study (2): Higher energy beam for Recent study (2): Higher energy beam for the detector in Korea the detector in Korea Flux (arb. unit) 1.0 to 2.5 degree off axis beam available in Korea. P( ν � � ν e ) Energy Dependent Energy Dependent Maximum Likelihood Maximum Likelihood Analysis Analysis E ν (GeV)
ν ν e ν ν ν ν ν ν selection likelihood distributions e selection likelihood distributions F.Dufour, NP08 After the “single-ring, electron-like” cut: ν e BG Good signal and Good signal and noise separation in noise separation in the sub-GeV region. the sub-GeV region. (The separation (The separation gets worse with the gets worse with the increasing energy.) increasing energy.)
Signal and BG for different off- -axis beams axis beams Signal and BG for different off (water Cherenkov detector) (water Cherenkov detector) F.Dufour, NP08 Normal hierarchy ��� � � θ �� ����� Korea (1050km) Korea (1050km) Kamioka (295km) Kamioka (295km) (2.5 deg.) 2.5 deg. 1.0 deg. (2.5 deg.) 2.5 deg. 1.0 deg. 60 60 400 1GeV 1GeV 1GeV Smaller off-axis angle: Smaller off-axis angle: � Larger matter effect at the 1st osc. Max.. � Larger matter effect at the 1st osc. Max.. � Low E BG more serious. (2nd osc. Max. slightly more difficult to see.) � Low E BG more serious. (2nd osc. Max. slightly more difficult to see.)
σ σ sensitivities for different OA angles σ σ 2 and 3 σ σ σ σ sensitivities for different OA angles 2 and 3 with the Kamioka + Korea setup (1) with the Kamioka + Korea setup (1) F.Dufour, NP08 Conditions: Conditions: Mass hierarchy Mass hierarchy (Updated ) ◆ 1.66 MW ◆ 1.66 MW -1� ◆ 5 years neutrino run + ◆ 5 years neutrino run + 10� sin 2 2 θ 13 3 σ normal 5 years anti-neutrino run 5 years anti-neutrino run ◆ 0.27Mton water Ch. detectors ◆ 0.27Mton water Ch. detectors -2� in Kamioka and Korea in Kamioka and Korea 10� 2 σ Systematic errors considered: Systematic errors considered: ◆ BG normalization (for Kam.) 5% ◆ BG normalization (for Kam.) 5% ◆ BG normalization (for Korea) 5% ◆ BG normalization (for Korea) 5% 0 0 1 1 2 2 3 � 3 � 4 4 5 5 6� 6� � � � ◆ BG normalization between ν e and ◆ BG normalization between ν e and -1� OA=1.0 (new syst) 10� anti- ν e 5% anti- ν e 5% OA=2.5 (new syst)û� inverted ◆ BG spectrum shape 5% ◆ BG spectrum shape 5% � ◆ σ ( ν � )/ σ ( ν e ) 5% ◆ σ ( ν � )/ σ ( ν e ) 5% ◆ ( σ ( ν � )/ σ ( ν e )) / -2� ◆ ( σ ( ν � )/ σ ( ν e )) / 10� ( σ (anti- ν � )/ σ (anti- ν e ) 5% ( σ (anti- ν � )/ σ (anti- ν e ) 5% ◆ Efficiency and energy scale diff. ◆ Efficiency and energy scale diff. between Near, Kam and Korea between Near, Kam and Korea δ 0 1 2 3 � 4 5 6� � detectors (3 error terms) detectors (3 error terms)
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