j-parc e61 experiment - events.ncbj.gov.pl · the tokai-to-kamioka (t2k) experiment c. vilela tmex...
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![Page 1: J-PARC E61 EXPERIMENT - events.ncbj.gov.pl · THE TOKAI-TO-KAMIOKA (T2K) EXPERIMENT C. Vilela TMEX September 20, 2018 2 50 kton World-leading measurements of sin2θ 23 and Δm2 23](https://reader034.vdocuments.mx/reader034/viewer/2022050716/5e17b1123df868725e7b77dc/html5/thumbnails/1.jpg)
J-PARC E61 EXPERIMENTREDUCING CROSS-SECTION UNCERTAINTIES IN NEUTRINO
OSCILLATION EXPERIMENTS
TMEX
WARSAW
SEPTEMBER 20TH, 2018
Cristóvão Vilela
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THE TOKAI-TO-KAMIOKA (T2K) EXPERIMENT
September 20, 2018C. Vilela TMEX 2
50 kton
World-leading
measurements
of sin2θ23 and
Δm223.
Super-Kamiokande J-PARCNear Detectors
Neutrino Beam
295 km
Mt. Noguchi-Goro2,924 mMt. Ikeno-Yama
1,360 m
1,700 m below sea level
Detectors 2.5° away from beam axis.
NOW 2018 NOW 2018
Exclusion of CP
conservation in
lepton sector
at 2σ.
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HYPER KAMIOKANDE PROJECT
September 20, 2018C. Vilela TMEX 3
260 kton Main ring upgrade
Super-Kamiokande J-PARCNear Detectors
Neutrino Beam
295 km
Mt. Noguchi-Goro2,924 mMt. Ikeno-Yama
1,360 m
1,700 m below sea level
Detectors 2.5° away from beam axis.
Proposed ND upgrade
• Next-generation water Cherenkov detector with extensive
Physics program.
• 5σ sensitivity for a wide range of δCP values.
• Requires strong constraints on systematic uncertainties.
• A kiloton-scale intermediate water Cherenkov detector is
foreseen as part of the strategy to mitigate the effect of
neutrino interaction uncertainties: E61
High QE PMTs
Hyper Kamiokande
E61
Assuming 3% uncertainty
Hyper-K single tank
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MEASURING NEUTRINO ENERGY
September 20, 2018C. Vilela TMEX 4
• Model assumptions play important role in inferring neutrino energy
from detected neutrino-nucleus interaction products.
• In Super-K charged lepton kinematics are measured and CCQE
dynamics are assumed.
• Multi-nucleon contributions to CCQE cross-section can bias Eν significantly.
• Large uncertainties from final state and secondary interaction models.
• Calorimetric measurements suffer from similar model dependence.
• For example, through uncertainties in the multiplicity of (undetected)
neutrons. T. Katori, M. Martini, arXiv:1611.07770
M. Martini et al, arXiv:1211.1523
Eν smearing due to Martini 2p2h.
Comparison of 2p2h event
rates from competing models
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NEAR DETECTOR CONSTRAINTS
September 20, 2018C. Vilela TMEX 5
• Neutrino flux is different in far detector compared to near detector:
neutrinos oscillate!
• This presents an additional difficulty in constraining neutrino interaction
models.
• We only ever measure a combination of flux and cross-section.
• Multi-nucleon effects can smear reconstructed neutrino energy into
oscillation dip at far detector, biasing the measurement.
• But this is obscured by the flux peak at the near detector!
Martini model Martini model
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THE E61 DETECTOR
• An intermediate water Cherenkov detector on the J-PARC
beam path.
• Instrumented portion of the detector is moveable within a
deep pit.
• Sample neutrino interactions from a wide range of off-axis
angles.
• Optically separated inner and outer detector volumes.
• Inner detector 6 – 10 m tall and 8 m diameter.
• Outer detector 10 – 14 m tall and 10 m diameter.
• Populated with multi-PMT modules.
• Details in G. de Rosa’s talk today at 11:25
• Aim to load water with Gadolinium.
• Precise measurements of neutron emission in neutrino
interactions.
September 20, 2018C. Vilela TMEX 6
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C. Vilela TMEX
2.5º
4º
1º
OFF-AXIS ANGLE SPANNING TECHNIQUE
September 20, 2018 7
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September 20, 2018C. Vilela TMEX 8
COMBINING OFF-AXIS SAMPLES
Eν spectrum l± observables
-0.5
+1.0
-0.2
• Make use of the off-axis
angle dependence of ν flux:
1. Bin data in off-axis angle.
2. Take combinations of
different off-axis angle
bins.
3. Get distribution of
observables for a known
Eν spectrum.
• Coefficients determined by
the desired Eν spectrum.
-0.5
+1.0
-0.2
Gaussian
Eν flux!Take linear
combinations of 60
off-axis angle bins.
Observables
corresponding to
Gaussian flux.
Apply same
coefficients to
distributions of
observables.
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PSEUDO-MONOCHROMATIC BEAMS
September 20, 2018C. Vilela TMEX 9
• Single muon candidate events after off-axis coefficients are applied to give
monochromatic flux centered at 1.2 GeV.
• Measure cross-sections as a function of true neutrino energy.
• Q2 and ω available – detailed neutrino measurements a la electron scattering.
• Powerful probe of interaction models, such as departures from CCQE due to
multinucleon effects.
True EνReconstructed Eνassuming CCQE
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E61 SIMULATION AND RECONSTRUCTION
September 20, 2018C. Vilela TMEX 10
Simulation of electron
particle gun event in E61
populated with mPMTs
• Complete simulation and reconstruction chain has
been developed for E61.
• In use for physics and detector optimization studies
• The Geant4-based WCSim package is used for
simulation.
• Highly configurable water Cherenkov detector
geometries, several PMT models available.
• Recently implemented multi-PMT modules.
pe
Electron/Muon
separation in
E61 populated
with 8” PMTs
• Reconstruction with fiTQun.
• Maximum likelihood estimation of
track parameters using all the
information in an event.
• Hit/unhit, time and charge.
• Developed and deployed at Super-K,
now also running on WCSim output.
Same software chain as Hyper-KC. Vilela DPF 2017
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E61 DETECTOR OPTIMIZATION STUDIES
September 20, 2018C. Vilela TMEX 11
• Complete simulation and reconstruction chain using WCSim and fiTQun is
being actively used in detector optimization studies.
• Study major detector parameters such as overall dimensions, photosensor size
and density, mPMT module configuration.
• Parameters are optimized as a function of detector performance:
• Electron / muon separation; electron / π0 separation, detection efficiencies, …
PMT size – granularity Detector height
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𝜈𝜇 EVENT SELECTION
September 20, 2018C. Vilela TMEX 12
Selected
single-ring
μ-like events2 – 3°
3 – 4°
νμCC selection
efficiency
2 – 3°
Oscillation maximum
• Event selection developed
using complete chain of
simulation and reconstruction.
• Single-ring, μ-like and fully
contained events.
• Shown here for detector
populated with 8″ PMTs.
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𝜈𝜇 DISAPPEARANCE WITH E61
September 20, 2018C. Vilela TMEX 13
True Eν
Far detector
prediction
• Take linear combinations of off-axis binned data to reproduce the far detector
oscillated neutrino flux.
• Use the corresponding observables to make a prediction for the far detector
data with little model dependence.
• Background, flux and acceptance corrections necessary for SK prediction.
• Significant uncertainty cancellation in neutral-current background subtraction.
• In oscillation dip region prediction is dominated by E61 data.
Very good fit
in dip region!
E61
E61
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E61 DATA-DRIVEN CONSTRAINTS
• Disappearance analysis using off-
axis angles combinations is shown
to be robust against interaction
mismodelling.
1. Produce fake data with throws
of flux and cross-section
uncertainties both with and
without multi-nucleon effects.
2. Fit the fake data using
interaction model without multi-
nucleon contributions.
• E61 significantly reduces
uncertainty and removes bias.
• This is a data-driven constraint,
independent of model choice.
September 20, 2018C. Vilela TMEX 14
Nieves 2p2h
T2K + E61
σ = 1.1%
-0.06% bias
T2K only
σ = 3.6%
0.3% bias
Martini* 2p2h
T2K + E61
σ = 1.2%
-0.1% bias
T2K only
σ = 3.2%
-2.9% bias
* “Hacked” model, with Nieves final states.
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𝜈𝑒 CROSS SECTION MEASUREMENT
• Uncertainty on 𝜈𝜇 to 𝜈𝑒 cross-section
ratio contributes significantly to total
error on T2K CP violation search.
• Current uncertainty of 3% is theory
motivated PRD86 (2012) 053003
• Relative 𝜈𝑒 flux increases with off-axis
angle – make a direct measurement of
the 𝜈𝑒 cross-section on water with E61.
• In momenta of interest for T2K expect
3% statistical uncertainty, with total
uncertainty of 6%.
• Using 2012 T2K systematics.
• Systematic uncertainties dominated by
flux and cross section.
• Expect reduction in uncertainty with
improved external measurements.
September 20, 2018C. Vilela TMEX 15
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E61 TEST BEAM EXPERIMENT
September 20, 2018C. Vilela TMEX 16
• Achieving the goals of Hyper-K requires a
reduction in current levels of detector
systematic uncertainty in water Cherenkov
experiments.
• Even a small shift in energy scale or
Cherenkov light emission profile can lead to
significant bias.
• Will need to develop a bottom-up approach
for detector systematic uncertainty estimation.
• Directly measure uncertainties on simulation
parameters in fits to calibration data.
• Constrain these uncertainties by directly
measuring water Cherenkov detector charged
particle response in a test beam experiment.
• Validate calibration and systematic uncertainty
estimation procedures.
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September 20, 2018C. Vilela TMEX 17
cos 𝜃
Muons in
Hyper-K
Geant4 model assumed for reconstruction
Geant3 model assumed for reconstruction
Longitud
inal ve
rtex b
ias
[cm
]
True momentum [MeV/c]
Ra
tio to G
ena
t3
N
umb
er
of
pho
tons
E61 TEST BEAM EXPERIMENT
FiTQun reconstruction
• Achieving the goals of Hyper-K requires a
reduction in current levels of detector
systematic uncertainty in water Cherenkov
experiments.
• Even a small shift in energy scale or
Cherenkov light emission profile can lead to
significant bias.
• Will need to develop a bottom-up approach
for detector systematic uncertainty estimation.
• Directly measure uncertainties on simulation
parameters in fits to calibration data.
• Constrain these uncertainties by directly
measuring water Cherenkov detector charged
particle response in a test beam experiment.
• Validate calibration and systematic uncertainty
estimation procedures.
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E61 TEST BEAM EXPERIMENT
September 20, 2018C. Vilela TMEX 18
• Considering the test beam experiment as an initial
step in a staged approach building E61.
• Populated with initial production of around 150
multi-PMT modules.
• A 3 – 4 m diameter tank accepts particle tracks
with length equivalent to those in the middle of
the full scale detector.
• Expect similar reconstruction performance.
• Require tertiary beam lines with momenta ranging
from 140 MeV/c to 1200 MeV/c.
• 𝑒, 𝜇± , 𝜋±, 𝐾± and 𝑝
• Options at Fermilab and CERN under
consideration.
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SCHEDULE
September 20, 2018C. Vilela TMEX 19
• Construction schedule is driven by multi-PMT module production.
• Aim to run the test beam experiment for two years starting in 2021.
• Full-scale detector construction concurrent with test experiment operation.
• Aim for full-scale experiment to be taking neutrino data in 2025, one year
before the start of Hyper-K.
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SUMMARY
• Long-baseline oscillation experiments are entering an era where
neutrino interaction and detector uncertainties will become
significant.
• Poorly understood feed-down effects can bias measurements and are
difficult to constrain with traditional near detectors as they are exposed to
a different flux.
• Significant improvements from current levels of detector systematic
uncertainties are required for the next generation experiments and subtle
detector mis-modelling can lead to large biases in oscillation parameter
estimation.
• The E61 off-axis angle spanning technique gives a data-driven
method to convert Erec to Etrue, decoupling the flux shape from
interaction models.
• In an initial phase of the experiment, a test beam setup is proposed
which will allow for precise characterisation of water Cherenkov
detectors response to charged particles.
September 20, 2018C. Vilela TMEX 20
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THANK YOU!
September 20, 2018C. Vilela TMEX 21
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GADOLINIUM LOADING
• Program to load Super-K water with Gadolinium is now
well established.
• Required tank liner refurbishment work ongoing.
• Aside from IBD, Gd will be useful for higher energy
physics at Super-K:
• Statistical separation of ν/anti-ν interactions in the
atmospheric samples, as well as wrong-sign background
reduction in beam samples.
• Significant background reduction for proton decay searches.
• However, large uncertainties on neutron multiplicity
lead to background uncertainties on the above.
• Near detector measurements with Gd critical for the
precise use of neutron capture information.
• Option to load E61 water with Gd provides an
opportunity to measure neutron emission rates and
capture on Gd as a function of Eν.
September 20, 2018C. Vilela TMEX 22
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MULTI-PMT MODULES
• Modules contain 3″ PMTs facing both the inner and outer detector volumes.
• Aluminium reflectors give an effective increase in photosensor area of ~20%.
• Modules contain integrated HV and read-out electronics.
• Expected Physics benefits:
• Improved time resolution: particularly important for resolving inter-bunch pileup.
• Finer granularity allows Cherenkov rings to be imaged with a better resolution:
expected reconstruction improvements.
• Reflectors and PMT orientation might provide additional directional information.
• Extensive R&D programme with significant international collaboration:
• Photosensor testing and characterization.
• Development of integrated electronics.
• Optical testing of materials: acrylic, silicon gel, …
• Mechanical modelling and prototyping.
September 20, 2018C. Vilela TMEX 23
• The E61 baseline design has the detector populated with multi-PMT modules.
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PROPOSED EXTENDED RUN OF T2K (T2K-II)
September 20, 2018C. Vilela TMEX 24
50 kton Main ring upgradeProposed ND upgrade
• Proposal to extend T2K run from 7.8x1021 to
20x1021 POT.
• Benefit from:
• Accelerator upgrade to 800 kW (and then 1.3 MW).
• Proposed near detector upgrade.
• Proposed intermediate water Cherenkov detector: E61
• 3σ sensitivity to maximal CP violation.
K. Abe et al, arXiv:1609.04111
Super-Kamiokande J-PARCNear Detectors
Neutrino Beam
295 km
Mt. Noguchi-Goro2,924 mMt. Ikeno-Yama
1,360 m
1,700 m below sea level
Detectors 2.5° away from beam axis.