Near Detectors for the Hyper-K Experiment Mark Hartz TRIUMF & Kavli IPMU TAUP 2019, Toyama, September 12 1
Near Detectors Hyper-Kamiokande Experiment Hyper-Kamiokande Water Cherenokov detector with 187 kton fiducial mass (8x larger than Super- Kamiokande) Broad physics program including neutrino oscillations with accelerator neutrinos 1.3 MW beam from J-PARC (2.5x higher than current T2K beam power) New near/intermediate detectors to control systematic uncertainties 2
Broad Physics Program Strong non-accelerator component of physics program: Supernova relic neutrinos Atmospheric neutrinos Nucleon decay Solar neutrinos Supernova burst 3
CP Violation with Accelerator Neutrinos arXiv:1805.04163 2058 events 1906 events Current long baseline experiments observe 10s of neutrino and antineutrino candidates Hyper-K will observe ~2000 electron neutrino and electron antineutrino candidates each 3% statistical error on the CP violation measurement will be achieved Controlling systematic errors is critical: T2K’s current errors are ~6% Near detectors address uncertainties on flux and interaction models 4
CP Violation with Accelerator Neutrinos arXiv:1805.04163 2058 events 1906 events Current long baseline experiments observe 10s of neutrino and antineutrino candidates Hyper-K will observe ~2000 electron neutrino and electron antineutrino candidates each 3% statistical error on the CP violation measurement will be achieved Controlling systematic errors is critical: T2K’s current errors are ~6% Near detectors address uncertainties on flux and interaction models 4
Neutrino Beam Modeling Systematic Errors μ ± (—) ν μ p π ± 5
Neutrino Beam Modeling Systematic Errors μ ± (—) ν μ p π ± Particle production modeling constrained by hadron production measurements 5
Neutrino Beam Modeling Systematic Errors μ ± (—) ν μ p π ± 5
Neutrino Beam Modeling Systematic Errors p 5
Neutrino Beam Modeling Systematic Errors μ ± (—) ν μ p π ± Beam direction uncertainty = uncertainty in peak energy in off-axis beam 5
Neutrino Beam Modeling Systematic Errors p 5
Neutrino Beam Modeling Systematic Errors π ∓ μ ∓ (—) ν μ p Wrong-sign (defocussed) component of the beam is important background when searching for CP violation 5
Neutrino Interaction Modeling Systematic Errors (I) Primary scattering process on a single bound nucleon l - ν Nucleon below threshold in water Cherenkov W + detector n p n Energy inferred from charged lepton kinematics p n p n p p p n p n 6
Neutrino Interaction Modeling Systematic Errors (I) Primary scattering process on a single bound nucleon l - ν Nucleon below threshold in water Cherenkov W + detector n p n Energy inferred from charged lepton kinematics p n p n p p p n p n 6
Neutrino Interaction Modeling Systematic Errors (I) Primary scattering process on a single bound nucleon l - ν Nucleon below threshold in water Cherenkov W + detector n p n Energy inferred from charged lepton kinematics p n p n p p p p n Nuclear e ff ects modify cross section and change p n energy inference Dominant source of systematic uncertainty 6
Neutrino Interaction Modeling Systematic Errors (I) Primary scattering process on a single bound nucleon l - ν Nucleon below threshold in water Cherenkov W + detector n p n Energy inferred from charged lepton kinematics p n p n p p p p n Nuclear e ff ects modify cross section and change p n energy inference Dominant source of systematic uncertainty Events 0 MeV < E < 300 MeV ν 300 MeV < E < 500 MeV ν 1.5 500 MeV < E < 700 MeV ν Feed-down from high energy is critical for θ 23 700 MeV < E < 900 MeV ν 900 MeV < E < 1100 MeV ν measurement 1100 MeV < E < 1700 MeV 1 ν 1700 MeV < E ν Need to measure the energy resolution function 0.5 0 0.5 1 1.5 2 2.5 6 E (Gev) rec
Neutrino Interaction Modeling Systematic Errors (II) Fractional di ff erence of electron (anti)neutrino and muon Lepton mass is also important (anti)neutrino cross sections For CP violation search: Muon neutrinos at near detectors Electron neutrinos at far detector >3% theoretical error on [ σ ( ν μ )/ σ ( ν e )] / [ σ ( ν μ )/ σ ( ν e )] Sources of theoretical error Phase space di ff erences Form factor uncertainties in lepton mass dependent cross section terms Radiative corrections 7 Phys.Rev. D86 (2012) 053003
Hyper-K Near Detector Suite Off-axis spanning intermediate Off-axis Magnetized Tracker On-axis Detector (INGRID) water Cherenkov detector (IWCD) (ND280 → ND280 Upgrade → ??) 4º Beam Direction 50 m 1º PVC vesse Scin 750 m panel ✦ On-axis detector: measure beam direction, monitor event rate ✦ Off-axis magnetized tracker: charge separation (measurement of wrong-sign background), study of recoil system ✦ Expect upgrades of detector inherited from T2K will be necessary ✦ Off-axis spanning water Cherenkov detector: intrinsic backgrounds, electron (anti)neutrino cross-sections, neutrino energy vs. observables, H 2 O target, neutron multiplicity measurement 8
INGRID Detector NIMA,V694, (2012), 211-223 On-axis Detector (INGRID) ✦ 14 modules in cross configuration on beam direction ✦ Iron and scintillator layers with 7 tons of target mass per module ✦ Monitor neutrino event rate to ensure stable beam operation ✦ Measure the beam direction with <0.25 mrad accuracy ✦ Uncertainty on predicted peak energy of neutrino spectrum <2 MeV 9
Upgraded ND280 Detector ✦ T2K is in the process of upgrading the magnetized ND280 detector ✦ Planned installation in 2021 and operation from 2022 ✦ New Super-FGD and horizontal TPCs replace the P0D ✦ ND280 upgrade TDR: CERN-SPSC-2019-001 (arXiv:1901.03750) TOF detector give better relative timing to improve direction measurement of particles ✦ A well understood detector from day one of Hyper-K operation ✦ Additional upgrades for Hyper-K for performance and longevity ✦ Upgrades informed by T2K measurement program 10
Upgraded ND280 Physics ✦ New TOF detectors allow to better distinguish direction of high angle muons ✦ Necessary for wrong-sign measurement ✦ High-angle TPCs give full angular coverage for track reconstruction ✦ Super-FGD target improves reconstruction of the hadronic recoil system ✦ Good timing and spatial resolution to detect neutron scatters and reconstruct energy by TOF ✦ Improved capability to probe nuclear effects and do calorimetric energy reconstruction 11
Intermediate Water Cherenkov Detector 4º B e a m PMTs Acrylic dome D 50 m i r e c t i o n 1º PVC vessel Stainless steel Scintillator Readout 750 m backplate panel electronics ✦ 1 kton scale water Cherenkov detector located ~750 m from the neutrino production point ✦ Position of detector can be moved vertically to make measurements at different off-axis angle to probe relationship of neutrino energy and final state lepton kinematics ✦ Can be loaded with Gd to measure neutron multiplicities in neutrino interactions ✦ Use multi-PMT photosensors with excellent spatial (80 mm) and timing (1.6 ns FWHM) resolution 12
Off-axis Angle Analysis Method 15 × 10 Arb. Norm. 4.0 Off-axis Flux ° 30 25 20 -0.4 +0.4 15 10 Observed muon 5 Spectra at at 0 0 0.5 1 1.5 2 2.5 3 3.5 kinematic E (GeV) � each off-axis bin 15 × 10 distributions Arb. Norm. 35 2.5 Off-axis Flux ° 30 25 +1.0 20 -1.0 15 10 5 0 0 0.5 1 1.5 2 2.5 3 3.5 E (GeV) � 15 × 10 Arb. Norm. 1.0 Off-axis Flux ° 25 -0.5 20 15 10 5 0 0 0.5 1 1.5 2 2.5 3 3.5 E (GeV) � Linear Combination, 0.9 GeV Mean 9 10 × Subtract off low energy and high energy Events/50 MeV 20 Arb. Norm. 1 Ring µ Event Spectrum 6000 Linear Combination Absolute Flux Error 1.7 Off-axis Flux ° sidebands of flux → produce very narrow Shape Flux Error 15 Gaussian: Mean=0.9, RMS=0.11 GeV Statistical Error 4000 NEUT QE beam to measure energy response. NEUT Non-QE 10 2000 5 0 Measure non-quasi-elastic component with 0 0 1 2 3 0 0.5 1 1.5 2 2.5 3 E (GeV) rec 13 E (GeV) 5% uncertainty ν
Electron (anti)Neutrino Cross Section π + ID ✦ Use intrinsic electron (anti)neutrino flux from γ muon and kaon decays (<1% of beam) γ ✦ Water Cherenkov is ideal for the electron OD (anti)neutrino cross section measurement μ - ✦ Large active volume allows for veto of Sand background from externally produced high energy gammas Selected 1-ring e-like events 900 ν e Other 800 ν ✦ Measurements at larger off-axis angle have high µ 0 ν π 700 µ flux fraction NC Other 600 0 NC π NC γ 500 Entering ✦ Simulation studies show 3.5-7% precision γ 400 signal ν e 300 ✦ Reduction of systematic errors under 200 investigation 100 0 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 14 Reconstructed neutrino energy (MeV)
Water Cherenkov Test Experiment ✦ 1% level calibration is critical for IWCD ✦ Plan test experiment in tertiary beam to evaluate detector response and calibration procedure ✦ Operation with p,e, π ± , μ ± , n with momentum range from 140 MeV/c-1200 MeV/c ✦ Planning operation at CERN after long shutdown (LS2) 4 m 4 m 15
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