Near detector T2K experiment

1 near detector

1.1 time projection chambers
1.2 fine-grained detectors
1.3 pi 0 detector
1.4 side muon range detector
1.5 electromagnetic calorimeter
1.6 data acquisition

near detector

nd280 under construction

the near detector 280 meters (nd280) graphite target segmented detector composed of neutrino targets inside tracking system surrounded magnet taken ua1 experiment. nd280 able measure neutrino beam s energy spectrum, flux, flavor content, , interaction cross-sections before neutrino oscillation. detector located 280 m target in off-axis direction.

time projection chambers

three time projection chambers (tpcs) able measure momenta of muons produced charged current reactions in detector, information yield neutrino energy spectrum. tpcs can used particle identification.

fine-grained detectors

two fine-grained detectors (fgds) placed after first , second tpcs. fgds , tpcs make tracker portion of nd280. fgds provide active target mass neutrino interactions , able measure short tracks of proton recoil.

the first fgd composed of 30 layers of 192 segmented scintillating bars, alternating between vertical , horizontal layers, while second fgd composed of 14 alternating layers of segmented scintillating bars , 6 water modules. each bar has hole down center containing wavelength shifting fiber collects of light scintillation , read out mppc @ 1 end. other end of fiber mirrored aluminum in order increase overall light yield reaching mppc. mirrored end has led light injection system calibration , testing integrity of fibers. second fgd partially composed of water because detector @ super-kamiokande water-based. water maintained under subatmospheric pressure ensure in case of leak air sucked in rather water spill out inside fgd. cross sections on carbon , on water can determined comparison of neutrino interactions in 2 fgds.

pi 0 detector

the pi 0 detector (
π0
) composed of layers of triangular scintillating plastic bars embedded wavelength shifting fibers channel light. thousands of multi-pixel photon counters(mppcs) used receive photon counts synchronously detect particle events. these particle events correlated proton beam spill timings , reconstructed using geometric , intensity data of photon counts. p0d used measure neutral pions produced in neutral current interactions. tracker , pi 0 detector surrounded electromagnetic calorimeter , side range muon detector. detection of pi0s important because 1 of major backgrounds of detecting neutrinos @ superk.

side muon range detector

the side muon range detector (smrd) consists of scintillator modules inserted gaps in magnet. smrd records muons escaping inner parts of detector @ large angles respect beam direction. can act trigger cosmic rays. can identify beam interactions in surrounding walls , in magnet itself.

electromagnetic calorimeter

the electromagnetic calorimeter (ecal) surrounds inner detectors (p0d,tpcs,fgds) , consists of scintillator bars , lead absorber sheets between layers of scintillators. ecal has 13 modules: 1 downstream of last tpc, 6 surrounding p0d , 6 surrounding tracker.

data acquisition

data acquisition t2k near detector implemented british, canadian , spanish collaborators using midas.