J-PARC neutrino experiment (T2K) 2019-July-10, Summer Student - PowerPoint PPT Presentation

J-PARC neutrino experiment (T2K) 2019-July-10, Summer Student Program K.Sakashita(KEK/J-PARC) 1

Neutrino 2

It’s special, mysterious particle.. ν e ν e ν e ν e ν e ν e ν e ν e ν e Abundant in Universe

m ν /m e < 10 -6 m ν /m e < 10 -6 It’s special, mysterious particle.. H.Murayama Tiny but non- zero mass Its properties are of great importance 
 in particle- and astro-physics

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Nobel Prize in 2015 June 1998 First firm evidence for NEUTRINO conference neutrino oscillation @ Takayama, Japan T.Kajita p, He ... p, He ... L = 10~30km L = 10~30km ν ν ν ν ν ν L=13000km L=13000km p, He ... p, He ... 6 p, He ... p, He ...

Accelerator based neutrino oscillation experiments E ν ν e appearance(2013) Discovery of T2K(L=295km) (-2009) (1999-2005) MINOS(L=735km) K2K(L=245km) (2009-) L neutrino proton neutrino beam production accelerator near far detector detector � 1 . 27 ∆ m 2 L ⇥ P ( ν α → ν β ) = sin 2 (2 θ ) sin 2 E ν 10 T2K data Best fit spectrum Number of events /(50 MeV) 8 Background component 18 events/0.2GeV ν μ candidates 6 16 14 data MC w/o ν osc. 12 4 MC w/ ν osc. 10 8 2 6 4 0 0 500 1000 2 Reconstructed neutrino energy (MeV) 0 0 1 2 3 4 5 rec E ν GeV

Particle-antiparticle symmetry Present 8 Earliest period q q q q q q q q q q q q q q q q q q q q q q • Particle-antiparticle asymmetry [CP violation(CPV)] is one of the conditions to create the matter dominant universe • If there is a neutrino-antineutrino asymmetry in the neutrino oscillation, it may be sufficient source of CPV to create the matter dominant universe ν µ ν e asymmetry ? ν e ν µ

9 Measuring CP asymmetry , , ν → ν ν → ν e µ e e µ 0.1 0.1 Osc. Prob. Osc. Prob. =0 , NH, =0 , NH, δ ° ν δ ° ν cp cp 0.08 0.08 =270 , NH, =270 , NH, δ ° ν δ ° ν cp cp 0.06 0.06 large difference 0.04 0.04 if CPV 0.02 0.02 0 0 0.5 1 1.5 2 2.5 3 0.5 1 1.5 2 2.5 3 E [GeV] E [GeV] ν ν

Detection of neutrino which is emitted from neutrino-matter interaction very small @1GeV (νn→μp) Huge size of detector & high intense ν beam is necessary l - • Detecting charged-lepton ! l W+ Nucleus • But, its interaction rate is • cross section ~10 -38 cm 2

11 T2K(Tokai-to-Kamioka) experiment Cherenkov detector Large size Water ν beam High intense T2K (Tokai to Kamioka) experiment ������� � ��������� � � � � High intensity � � beam from J-PARC MR to Super-Kamiokande @ Prob. ( ν µ → ν e ) Prob. (¯ ν µ → ¯ ν e ) � � � � � � � � � � � � � � � � � � �� � � � � � � �

T2K collaboration 12 International collaboration (as of 2019 Jan. : ~500 members, 68 institutes, 12 countries)

High intense neutrino beam Focusing beam proton dump Beam Decay volume device Target World highest proton intensity ~150m to Super-Kamiokande (far detector) → 8 x 10 7 of neutrinos are injected 
 target. mesons which are generated by injecting proton beam into the ( horn ) ν μ + - p π μ • High intense neutrino beam is generated from decays of π or K • ~99% of the generated neutrino is muon neutrino • (Present) 2.5 x 10 14 protons are injected every 2.5 second 


J-PARC & Neutrino beam-line 14 Linac 25Hz,330m H- 400MeV, 50mA 3GeV Synchrotron (RCS) 25Hz, 350m, Neutrino beam-line 1MW & Near detector Material/Life 30GeV MR Science Facility 0.3Hz, 1.6km, 485kW(present) 500m → 1.3MW Hadron Experimental Facility

Linac (DTL,SDTL) 30GeV MR Accelerating “proton”

J-PARC neutrino facility Producing a high intensity neutrino beam 16