HYPER-K SYSTEMATIC UNCERTAINTIES (BEAM RELATED)
Mark Hartz (TRIUMF & Kavli IPMU) Neutrino Beams and Instrumentation Workshop (NBI) Fermilab, 2019/10/24
1 OVERVIEW OF THIS TALK
➤ Brief introduction to Hyper-K
➤ Overview of systematic uncertainties for Hyper-K
➤ Proposed near detector suite
➤ Systematic uncertainties and beam modeling
2 THE HYPER-K EXPERIMENT Hyper-K
Super-K
Kamiokande
• Builds on the successful T2K and Super-Kamiokande experiments • Beam will be upgraded from current power of ~500 kW to 1.3 MW • Hyper-K will have an 8 times larger fiducial mass than Super-K • New photo-detector technologies -> improved photon detection • New near and intermediate detectors • Hyper-K will accumulate statistics for accelerator based program 20x faster than T2K currently does 3 ACCELERATOR-BASED PHYSICS AT HYPER-K
1 sin2θ =0.5 0.8 23 Hyper-Kamiokande 2 -3 2 ∆m32=2.5×10 eV
Osc. Prob. 0.6 2 sin 2θ13=0.085 0.4
0.2 νµ→νµ, νµ→νµ
0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
νµ→νe: NH, δcp = -π/2 • Muon (anti)neutrino survival ν →ν : IH, δ = -π/2 0.1 µ e cp 2 2 Osc. Prob. ν →ν : NH, δ = -π/2 sensitive to sin (2θ23) and Δm 32 µ e cp νµ→νe: IH, δcp = -π/2 • Electron (anti)neutrino appearance 0.05 2 2 sensitive to sin (θ23), sin (2θ13) and
2 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 1.5 6 2 21 Δm 32 in leading term, δcp in (×10 ) (/cm /50 MeV/1×10 POT) ν Mode, SK ν , No Osc. subleading terms, mass ordering 1 µ Mode, SK , No Osc. through matter effect ν νµ Neutrino Flux 0.5
0 0.5 1 1.5 2
Eν (GeV)
Broad physics program, see talk by A. Konaka on Monday 4 CP VIOLATION REQUIREMENT
2058 events 1906 events
• To first order, Hyper-K CP violation search is a counting experiment
• ~2000 events in neutrino and antineutrino mode
• Statistical uncertainty on asymmetry measurement is ~3% after 10 years
• Need systematic error reduction to this level
5 T2K SYSTEMATIC ERRORS
± νe Excess for CC(QE,2p-2h,π ), NEUT 5.3.4
µ 0.25 Error Source % Error on neutrino/ ν antineutrino rate σ )/ Sum of CC Modes µ ν
Pion Interactions 1.58 σ 0.2 - CC-QE Mode e ν σ
( CC-2p2h Mode Neutral Current Background 1.50 0.15 CC1π± Mode Electron (anti)neutrino cross 3.03 section 0.1 Extrapolation from near 2.31 detector 0.05 Removal Energy 3.74 0 0.5 1 1.5 2 Far Detector model 1.47 Eν (GeV) Total 5.87
• T2K systematic error primarily dominated by neutrino (or pion) interaction systematic uncertainties (red box)
• Largest is uncertainty on relative cross sections of νe and νe-bar (blue box)
• T2K error is only theoretical error on CCQE interactions
• Hyper-K should measure the cross section ratios: σ(νe)/σ(νμ) and σ(νe)/σ(νμ) 6 PRECISION CP PHASE - SYSTEMATIC EFFECTS
Neutrino Mode 1.06 arXiv:1805.04163 13° δ Shift CP 1.04 4 MeV Removal Energy Shift 0.5% Energy Scale Shift 1.02
Ratio to Nominal 1
0.98
0.96
0.94 0.2 0.4 0.6 0.8 1 1.2
Erec (GeV)
• Near the true value of δcp = ±90º, the measurement of δcp is less precise
• Because CP-conserving term dominates and effect is equivalent to energy scale shift in observed spectrum
• Energy scale uncertainties should be controlled at the 0.5% level
• Off-axis angle uncertainty should be <0.3 mrad
7 Atmospheric Parameters Muon neutrino candidates
0 MeV < Eν < 300 MeV
arXiv:1805.04163 2 300 MeV < Eν < 500 MeV Events 1.5 sin 2θ23 500 MeV < Eν < 700 MeV
700 MeV < Eν < 900 MeV
900 MeV < Eν < 1100 MeV 1100 MeV < E < 1700 MeV 1 ν 1700 MeV < Eν
0.5
0 0.5 1 1.5 2 2.5
Erec (Gev)
• We are interested in whether θ23 is consistent with maximal mixing (θ23=45º)
• Need a good understanding of events with reconstructed energies that feed down into the oscillation maximum region
8 Systematic Uncertainties
• Dominant systematic uncertainties in Hyper-K are generally from the interaction cross section modeling
• The extrapolation errors on the flux model are generally small
• However, flux uncertainties can enter into the measurements in a manner that does not allow for simple cancellation in the near/far ratio
• Will show a few near detector measurements and these types of flux uncertainties
9 BASELINE DESIGN FOR NEAR/INTERMEDIATE DETECTORS
Off-axis Magnetized Tracker Off-axis spanning intermediate On-axis Detector (INGRID) (ND280→ND280 Upgrade→??) water Cherenkov detector (IWCD)
4º
B e am D 50 m Acrylic dome PMTs ir ec ti on
1º PVC vessel
750 m Scintillator Readout Stainless steel panel electronics backplate
➤ 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, H2O target, neutron multiplicity measurement 10 BEAM DIRECTION MEASUREMENT
➤ For Hyper-K, ND280 and IWCD are not along same direction as far detector Hyper-K IWCD Super-K ND280
Beam direction
0.05
➤ Can introduce additional direction uncertainty 0.04 ND280 to SK ND280 to HK that doesn’t cancel in far/near ratio 0.03 ➤ Corresponds to a <2 MeV peak energy shift of 0.02 spectrum when considering simple off-axis angle uncertainty, assuming INGRID constraint F/N Ratio Fractional Error 0.01
➤ 0 What about second-order effects? 0 0.5 1 1.5 2 2.5
Eν (GeV) 11 RESIDUAL ERRORS WITH INGRID CONSTRAINT
➤ There are a number of systematic effects that to first order correspond to a shift of the beam direction IWCD ➤ Proton beam transverse position at target, horn and target alignment, horn field or material asymmetries…
➤ At second order, these systematic effects may not have the exact same signature at INGRID and Hyper-K
➤ An INGRID measurement of the off-axis angle will leave residual errors at Hyper-K
The fit to the beam direction at INGRID predicts the first-order change to the spectrum But bin-by-bin changes can be off by as much as 1-2% in the right- sign flux
12 STRATEGY FOR RESIDUAL SPECTRUM ERRORS
➤ We are making a full evaluation of these residual errors and their impact on the Hyper- K physics measurements IWCD ➤ If they need further constraint, there are two approaches
➤ Reduce the systematic error sources: better alignment, beam position measurement, horn field measurements, material modeling, etc.
➤ Consider additional beam profile monitors located away from the cross configuration of INGRID
13 THE IWCD
• The IWCD is 8 m tall, 10 m diameter water Cherenkov detector in a vertical pit
• Detector vertical position controlled with external water level (see below)
• Changing the vertical position changes the off-axis angle
• Neutrino spectrum varies with off-axis angle
• Can probe relationship between neutrino energy and observed final states in water Cherenkov detector
14 USING THE OFF-AXIS DATA
×1015
30 4.0° Off-axis Flux 25 Arb. Norm. 20 15 +0.4-0.4 10 5 Observed muon 0 0 0.5 1 1.5 2 2.5 3 3.5 Spectra at at E (GeV) kinematic ×1015 each off-axis bin 35 2.5° Off-axis Flux distributions 30
Arb. Norm. 25 20 +1.0 15 -1.0 10 5 0 0 0.5 1 1.5 2 2.5 3 3.5
E (GeV)
×1015
25 1.0° Off-axis Flux
Arb. Norm. 20
15 -0.5
10
5
0 0 0.5 1 1.5 2 2.5 3 3.5
E (GeV)
Linear Combination, 0.9 GeV Mean ×109 20 Linear Combination 6000 1 Ring µ Event Spectrum Absolute Flux Error 1.7° Off-axis Flux 15 Subtract off low energy and high energy Shape Flux Error Gaussian: Mean=0.9, RMS=0.11 GeV Statistical Error Arb. Norm. 4000 NEUT QE Events/50 MeV NEUT Non-QE 10 tails of flux → produce very narrow 2000 5 beam to measure energy response.
0 0 0 1 2 3 0 0.5 1 1.5 2 2.5 3 Erec (GeV) Eν (GeV) 15 FLUX UNCERTAINTIES IN IWCD ANALYSIS
➤ We study flux errors for the case where the linear combinations are used to reproduce the muon neutrino spectrum after disappearance ➤ Hadron production errors cancel well between linear combination IWCD flux and Hyper-K flux ➤ Errors that affect the beam profile (such as off-axis angle) don’t cancel as well ➤ We can benefit from strategies to reduce these
Pion Multiplicity Throw Proton Beam -1 mm Y Shift 1.15 1.15 HKSK MC (1σ Change)/Nominal 1.1 SKHK MC (Random Throw)/Nominal 1.1 νIWCDPRISM Linear Comb. (1σ Change)/Nominal νPRISM Linear Comb. (Random Throw)/Nominal 1.05 IWCD 1.05
1 1 SK Prediction Ratio SK Prediction Ratio 0.95 0.95
0.9 0.9
0.85 0.85 0.5 1 1.5 2 2.5 3 0.5 1 1.5 2 2.5 3 E (GeV) Eν (GeV) ν 16 ELECTRON (ANTI) NEUTRINO CROSS SECTION IN IWCD
➤ Use intrinsic electron (anti)neutrinos in beam to + ID measure their cross section γ ➤ Advantages in IWCD γ ➤ Active shielding minimizing high energy OD external gamma background - ➤ The fraction of electron (anti)neutrino flux Sand increases with off-axis angle
➤ Measurements are made relative to the Selected 1-ring e-like events 900 muon (anti)neutrinos νe 800 νµ Other 0 700 νµ π ➤ NC Other >70% pure samples of a few 600 NC π0 500 NC γ thousand candidates can be Entering γ 400 achieved νe signal 300
200 ➤ Statistics at low energy are 100
important 0 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 17 Reconstructed neutrino energy (MeV) ELECTRON (ANTI) NEUTRINO CROSS SECTION
0.12 Total error Total error 0.1 Total error Total error 0.09 0.1 Statistics only No detector 0.08 No flux No cross-section No cross-section 0.08 0.07 No detector Fractional error Fractional error No flux 0.06
0.06 Statistics only 0.05
0.04 0.04 0.03
0.02 0.02 0.01
0 0 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 Reconstructed neutrino energy (MeV) Reconstructed neutrino energy (MeV)
➤ Statistical errors are at the 2-4% level for bins of primary importances
➤ Controlling uncertainties on the flux and backgrounds will be important for achieving this level of precision
➤ Calibration is also important. Relative error on fiducial volume for muon neutrino and electron neutrino candidates must be controlled. 18 FLUX ERRORS FOR ELECTRON (ANTI)NEUTRINO MEASUREMENTS
• Measuring the cross section ratios σ(νe)/σ(νμ) and σ(νe)/σ(νμ)
• Depend on the flux ratios Φ(νe)/Φ(νμ) and Φ(νe)/Φ(νμ)
• IWCD studies are carried out with an older version of the flux uncertainties based on NA61/SHINE thin target data
• Have done preliminary investigation into errors with NA61/SHINE 2009 replica target data Eur. Phys. J. C76 (2016) no.11, 617
• Based on T2K flux error calculations (only at 2.5º off-axis)
• NA61/SHINE 2009 replica target data only for pion production
• Future T2K flux releases will be based on NA61/SHINE 2010 replica target data that includes kaon production measurements Eur. Phys. J. C79 (2019) no.2, 100
19 FLUX RATIO UNCERTAINTIES Neutrino Mode Antineutrino Mode 0.1 0.1 Total Work in progress Total Work in progress
Error Hadron Production Error Hadron Production µ µ ν 0.08 Off-axis Angle ν 0.08 Off-axis Angle Φ Φ / / e e
ν Beam Line Model ν Beam Line Model
Φ 0.06 Φ 0.06
0.04 0.04
0.02 0.02
0 0 10-1 1 10-1 1 Eν (GeV) Eν (GeV) ➤ Uncertainty just above flux peak is dominated by off-axis angle uncertainty ➤ No dominant source of beam line modeling errors. ➤ Would benefit from reduction of error on: horn current measurement, horn field measurement, beam line alignment, material modeling etc.
20 HADRON ERRORS Neutrino Mode Antineutrino Mode 0.1 0.1 Hadron Production Hadron Production Error Error
µ Untuned Interactions µ Untuned Interactions ν 0.08 ν 0.08
Φ Interaction Length Φ Interaction Length / / e e
ν Work in progress ν Work in progress
Φ 0.06 Φ 0.06
0.04 0.04
0.02 0.02
0 0 10-1 1 10-1 1 Eν (GeV) Eν (GeV) ➤ Uncertainties on the interaction length and un-tuned interactions dominate the hadron production errors ➤ Some of these are related to kaon production and kaon re-scattering ➤ Should revisit after 2010 replica target data is used
21 OFF-AXIS ANGLE ERROR
• Dominant source of error on beam direction is from beam vertical position/angle at the target
• Can be constrained by the INGRID measurement
22 CONCLUSION
➤ Controlling systematic errors is important for the Hyper-K physics program
➤ Standard flux errors on the near to far extrapolation aren’t dominant
➤ We consider other sources of errors
➤ Flux profile errors with left/right asymmetry
➤ Errors as a function of off-axis angle
➤ Errors on the Φ(νe)/Φ(νμ) and Φ(νe)/Φ(νμ) ratios
➤ Hyper-K is considering improved beam monitor and additional hadron production measurements to reduce these errors
23 THANK YOU
24