Recent results from the T2K experiment
Kamil Porwit for the T2K Collaboration
University of Silesia, Katowice, Poland
XVIII International Workshop on Neutrino Telescopes, Venice, 19.03.2019
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 1 / 38 Outline
1 Neutrino mixing
2 The T2K Experiment
3 Oscillation analysis method
4 T2K results
5 Future perspectives
6 Summary
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 2 / 38 Neutrino Mixing Neutrino Oscillations
There are three types of neutrinos: νe, νµ, ντ , −6 ν’s are very light: ∼ 4 × 10 me, neutrino of definite flavour is a linear superposition of mass eigenstates: X ∗ |νl i = Uli |νi i i
UPMNS =
τ 3 −iδ 1 0 0 c13 0 s13e c12 s12 0 0 c s 0 1 0 −s c 0 23 23 12 12 iδ 0 −s23 c23 −s13e 0 c13 0 0 1 e
1
2
µ
cij = cos(θij ), sij = sin(θij )
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 3 / 38 Neutrino Mixing Oscillation probabilities
Probability of flavour change:
2 ! ( ) ( ) ∆m L P(ν− → ν− ) = δ − 4 X Re(U∗ U U U∗ )sin2 ij α β αβ αi αj βi βi 4E i>j 2 ! (−) ∆m L +2 X Im(U∗ U U U∗ )sin2 ij αi αj βi βi 4E i>j
δαβ- Kronecker delta,
2 2 2 ∆mij = mi − mj , i, j = 1, 2, 3, α, β = e, µ, τ L - baseline, E - ν energy
P(να → νβ) 6= P(¯να → ν¯β) will violate CP invariance!
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 4 / 38 Neutrino Mixing Long baseline neutrino oscillations
Disappearance of νµ/ν¯µ :
(−) (−) 2 2 P(νµ → νµ) = 1 − 4cos (θ13)sin (θ23) ! h i ∆m2 L × 1 − cos2(θ )sin2(θ ) sin2 32 13 23 4E + (solar, matter effect terms)
2 location of dip:∆ m32 2 depth of dip: sin (θ23)
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 5 / 38 Neutrino Mixing Long baseline neutrino oscillations
Appearance of νe/ν¯e :
(−) (−) P(νµ → νµ) = ! ∆m2 L sin2(θ )sin2(2θ )sin2 32 23 13 4E
(+) h 2 2 − sin(2θ12)sin (2θ23)sin (2θ13)cos(θ13) ! ! ∆m2 L ∆m2 L × sin 21 sin2 32 sin(δ ) 4E 4E CP + (CP-even, solar, matter effect terms)
magnitude of the peak: 2 2 sin (θ23), sin (2θ13), δCP
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 6 / 38 Neutrino Mixing Current knowledge of oscillation parameters
To understand ν oscillations we need to measure all parameters: ◦ ◦ θ12 = 33.6 ± 0.8 - solar ν’s ◦ ◦ θ23 = 45.6 ± 2.3 - is θ23 maximal? ◦ ◦ θ13 = 8.3 ± 0.2 - recent reactorν ¯e disappearance measurements
δCP unknown → possibility of CP violation in the lepton sector mass hierarchy unknown:
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 7 / 38 The T2K experiment T2K overview
∼500 people from 12 countries, 66 institutes high intensity beam produced at J-PARC with νµ andν ¯µ mode off-axis technique to get narrower energy spectrum
main goals:
estimate δCP through νe appearance 2 measure θ23, |∆m32|, through νµ disappearance
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 8 / 38 The T2K experiment Beam production
30 GeV proton beam delivered by Linac→RCS→MR High intensity p+ beam hits the carbon target, magnetic horns focusing outgoing hadrons, ± ± (−) π decays to µ and νµ in 100m long decay volume, beam dump stops almost all µ particles, number of (ν−) ’s is proportional to number of p+ (% beam power ∼ % (ν−) flux)
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 9 / 38 The T2K experiment Off-axis beam properties
narrowed energy spectrum peaks at 0.6GeV
νµ flux peaked at maximum disappearance and appearance off-axis technique used in the experiment for the first time
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 10 / 38 The T2K experiment INGRID
On-axis beam detector: 16 modules (iron/scintillator sandwich) additional module with scintillators only
count νµ by reconstructing µ from interactions
goal: monitor beam rate, direction and stability
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 11 / 38 The T2K experiment ND280
Off-axis beam detector: sub-detectors in 0.2T field: P0D - π0, TPC - PID, track particles, FGD - target, vertex info., ECAL - PID for particles exiting ND280 (γ’s, π0’s) (ν−) cross-section measurements (−) measure νe contamination in the beam
goal: measure (ν−) event spectrum before oscillation occurs
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 12 / 38 The T2K experiment Far detector - Super-Kamiokande
SK far detector: ∼ 1km of screening rocks (2700 meter water equivalent) 50kt water Cherenkov technology > 11000 PMT’s excellent e/µ separation
goal: measure (ν−) event spectrum after oscillations occured
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 13 / 38 The T2K experiment
νµ disappearance signal νe appearance signal (µ-like) (e-like)
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 14 / 38 The T2K experiment T2K Data-Taking status
3.16 × 1021 Protons On Target (POT) latest oscillation results based on: 3.13 × 1021 =∼ 1.49 × 1021ν+ ∼ 1.63 × 1021ν¯ POT 40% of the total approved T2K statistics (7.8 × 1021 POT)
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 15 / 38 Oscillation analysis method Oscillation Analysis method
Number of ν events observed:
Eν bins flavours far X X far far far far N = Pνj →νk φj σk Mdet i j
Eν bins flavours near X X near near near near N = φj σk Mdet i j
compare observed rates at far detector constrain by observed rates at near detector depends on: Oscillation probabilities Neutrino flux Neutrino interaction cross section detection efficiency detector resolution
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 16 / 38 Oscillation analysis method Oscillation Analysis method
NA61/SHINE data ν flux ND280 data model INGRID/Beam ND280 model monitor data ND280 fit External cross section data ν cross SK data section model
ν oscillation SK model Oscillation fit model
Oscillation parameters
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 17 / 38 Oscillation analysis method T2K flux prediction
Predicted fluxes at SK: Simulations takes into account: hadron interactions: simulated by: Fluka + GEANT3 tuned to: NA61/SHINE data beam parameters horns parameters Largest uncertainties comes from: hadron interactions p+ beam profile + off-axis angle
Analysis improvements to include NA61/SHINE replica target data will significantly reduce hadron interaction errors
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 18 / 38 Oscillation analysis method Oscillation Analysis method
NA61/SHINE data ν flux ND280 data model INGRID/Beam ND280 model monitor data ND280 fit External cross section data ν cross SK data section model
ν oscillation SK model Oscillation fit model
Oscillation parameters
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 19 / 38 Oscillation analysis method Neutrino Cross Section Model
Main interaction at T2K ν energy is Charged Current Quasi-Elastic (CCQE): − νµ + n → µ + p
can reconstruct Eν using: m, E, ~p, θµ Charged Current single pion (CC1π): − + νµ + n/p → µ + π + n/p Neutral Current (NC) and Deep Inelastic Scattering (DIS) can be additional backgrounds
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 20 / 38 Oscillation analysis method Oscillation Analysis method
NA61/SHINE data ν flux ND280 data model INGRID/Beam ND280 model monitor data ND280 fit External cross section data ν cross SK data section model
ν oscillation SK model Oscillation fit model
Oscillation parameters
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 21 / 38 Oscillation analysis method ND280 role
Multiple data samples in ND280 are fitted to constrain the combination of flux and ν interaction systematics at SK
2 × 3 samples (C + H2O) for ν mode: νµCC0π, νµCC1π, CCOther
2 × 4 samples (C + H2O) forν ¯µ mode: ν¯µCC1Track, ν¯µCCNTrack, νµCC1Track, νµCCNTrack Data on carbon and oxygen targets are binned in outgoing µ momentum and angle
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 22 / 38 Oscillation analysis method ND280 fit
Before analysis: After analysis:
Data/Sim. ratio is closer to one after fit result of data fit reduces interaction and flux model uncertainties! Errors on SK reduced from: ∼ 15% to ∼ 5%
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 23 / 38 Oscillation analysis method Oscillation Analysis method
NA61/SHINE data ν flux ND280 data model INGRID/Beam ND280 model monitor data ND280 fit External cross section data ν cross SK data section model
ν oscillation SK model Oscillation fit model
Oscillation parameters
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 24 / 38 Oscillation analysis method SK data sample with fit
1-r CCQE-µ-like 1-r CCQE-e-like 1-r CC1π+-e-like
ν
MC assumption: ν¯ δCP = −π/2 Normal Hierarchy 2 sin (θ23) = 0.528 2 sin (θ13) = 0.0219
Fit is done simultaneously to all five data samples
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 25 / 38 Oscillation analysis method Oscillation Analysis method
NA61/SHINE data ν flux ND280 data model INGRID/Beam ND280 model monitor data ND280 fit External cross section data ν cross SK data section model
ν oscillation SK model Oscillation fit model
Oscillation parameters
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 26 / 38 T2K results
New T2Kν ¯e appearance result
Compare consistency with PMNSν ¯e appearance (β=1) and no ν¯e 0 appearance (β=0): P (¯νµ → ν¯e) = β × P(¯νµ → ν¯e) Rate analysis: expected number ofν ¯e events with oscillation (β = 1, 17.2 events)
expected number ofν ¯e events without oscillation (β = 0, 9.4 events) data agrees with both hypotheses result is not statistically conclusive - need more data
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 27 / 38 T2K results
New T2Kν ¯e appearance result Rate + shape analysis: expected number ofν ¯e events with oscillation (β = 1, 17.2 events)
expected number ofν ¯e events without oscillation (β = 0, 9.4 events) the β = 0 hypothesis is excluded by 2σ result is not statistically conclusive - need more data
Analysis P-value for β = 1( σ excl.) P-value for β = 0( σ excl.) Rate only 0.0686 (1.82σ) 0.246 (1.16σ) Rate + shape 0.0244 (2.25σ) 0.261 (1.12σ)
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 28 / 38 T2K results 2 2 T2K results: ∆m32 vs sin (θ23)
CL counturs for νµ → νµ disappearance parameters
reactor constrains on θ13 compatible with maximal mixing
Normal Hierarchy Inverted Hierarchy 2 +0.030 +0.029 sin (θ23) 0.532−0.037 0.532−0.035 2 −3 2 +0.070 +0.069 |∆m32| × 10 eV 2.452−0.071 2.432−0.071
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 29 / 38 T2K results 2 T2K results: δCP vs sin (θ13)
Preference for values δCP ∼ −π/2 Updated the reactor constrain to match PDG2018 2 value: sin (θ13) = 0.0212 Normal Hierarchy Inverted Hierarchy 2 +0.0055 +0.0059 T2K-only sin (θ13) 0.0268−0.0043 0.0300−0.0050
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 30 / 38 T2K results T2K results: CP violation
fit with reactor constrain on θ13
δCP 2σ confidence interval: NH: [−2.966, −0.628]rad IH: [−1.799, −0.979]rad
Best fit point:
Normal Hierarchy Inverted Hierarchy
δCP rad −1.885 −1.382
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 31 / 38 T2K results T2K results: CP violation - Bayesian Analysis
Both Hierarchies:
T2K excludes CP conservation at 2σ but not 3σ
Most probable value is δCP = −1.74rad
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 32 / 38 T2K results T2K results: cross-section measurements
Rich program of non-oscillation physics: neutrino interaction cross section measurements exotic physics searches (sterile neutrinos, heavy neutrinos) Recent cross-section results: νµ CC inclusive on CH: CC-inclusive on CH, FE, H2O
CC0π, CC1π on CH, H2O NC1π0 Ongoing cross-section analyses:
CC inclusiveν ¯µ on Ar
CC0π νµ on H2O, C 0 0 NC1π , CC1π on H2O ND1γ (PRD 98, 012004 (2018)) + many more! K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 33 / 38 Future perspectives Future prospects: T2K-II
Extension of T2K running period (T2K-II): stage 1 of the proposal has been accepted by KEK/J-PARC (7.8 × 1021POT→ 20 × 1021POT) Main Ring accelerator will be upgraded to increase the beam intensity (∼ 1.3MW ) upgrade of the ND280 will happen in 2021. Plan to reduce the systematic errors down to ∼ 4% expected 3σ CP violation sensitivity
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 34 / 38 Summary Summary
T2K provided one of the world’s best θ23 measurements
Rate + Shape analysis gives hint of 2σ ν¯e appearance from aν ¯µ beam
CP conserving values of δCP falls outside 2σ CL intervals T2K is producing a lot of cross-section results Need more DATA for both beam modes Various upgrades underway for increased beam power + improved systematics
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 35 / 38 Summary
Thank You for Your attention!
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 36 / 38 Summary Backup
Flux and errors for antineutrino mode:
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 37 / 38 Summary Backup
Flux after ND280 fit:
K. Porwit@NuTelescopes 2019 Recent results from the T2K experiment 38 / 38