Presented at ICRR annual review

1. S. Cao (IPNS, KEK)
on behalf of T2K Collaboration
08/12/17 ICRR Annual Review 2017
T2K Status in 2017
² The T2K experiment
² Neutrino beam status
² Detector status
² Highlight of latest results
² Future plans

2. The T2K experiment
08/12/17 ICRR Annual Review 2017 2
~500 researchers from 64 institutions in 12 countries
² Long-baseline neutrino experiment
² Neutrino produced at J-PARC & detected at T2K far detector, Super-Kamiokande
² Off-axis technique to optimize neutrino oscillation measurement.
² Near detectors to constrain flux & neutrino interaction model
² Discovered appearance of (2013)
² Leading effort of CP violation search
² Vibrant programs of non-standard physics & neutrino interactions
⌫µ ! ⌫e

3. J-PARC neutrino beam status
08/12/17 ICRR Annual Review 2017 3
AccumulatedPOT
0
5
10
15
20
25
2010 2011 2012 2013 2014 2015 2016
Run1 Run2 Run3 Run4 Run5 Run6 Run7 Run8
BeamPower(kW)
0
100
200
300
400
500
20
10×
Total Accumulated POT for Physics
-Mode Beam Powerν
-Mode Beam Powerν
23 January 2010 – 12 April 2017
Total POT: 22.54 x 1020
ν mode POT: 14.93 x 1020 (66.2%)
ν mode POT: 7.62 x 1020 (33.8%)
_
² Stable operation with 470kW beam power
² Double neutrino data in 1 year!
² Totally 22.50 x 1020 POT collected, ~30% of currently approved exposure

4. J-PARC neutrino beam status (cont’d)
08/12/17 ICRR Annual Review 2017 4
² Stability of 𝜈 production rate monitored by T2K on-axis INGRID detector
² Stability of 𝜈 beam direction monitored by INGRID and MUMON
(1mrad shift corresponds to 2% shift in 𝜈 peak energy)
Day
[events/1e14POT]
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
Event rate Horn250kA
Horn205kA
Horn-250kA
[mrad]
1−
0.5−
0
0.5
Horizontal beam direction INGRID
MUMON
Day
[mrad]
1−
0.5−
0
0.5
1
Vertical beam direction INGRID
MUMON
T2K Run1
Jan.2010-Jun.2010
T2K Run2
Nov.2010-Mar.2011
T2K Run3
Mar.2012-Jun.2012
T2K Run4
Oct.2012-May.2013
T2K Run5
May.2014
-Jun.2014
T2K Run6
Oct.2014-June.2015
T2K Run7
Feb.2016-May.2016
T2K Run8
Oct.2016-Apr.2017

5. T2K far detector status
08/12/17 ICRR Annual Review 2017 5
² Super-K performs stably
² Data taking efficiency of 98.8% for T2K run8
Super-Kamiokande
(41.4 m tall x 39.3m diameter)
22.5 ktons fiducial volume
1000m underground
2.5
12/31
2008
12/31
2009
12/31
2010
12/31
2011
12/31
2012
12/31
2013
12/31
2014
12/31
2015
12/31
2016Event/day
0
2
4
6
8
10
12
attenuationlength[m]
date
using bottom PMT
60
65
70
75
80
85
90
95
100
105
110
01/01/09 01/01/10 01/01/11 01/01/12 01/01/13 01/01/14 01/01/15 01/01/16 01/01/17
Atmospheric 𝜈 FCFV events

6. Analysis improvements
08/12/17 ICRR Annual Review 2017 6
² Super-K event selection & new data sample
² Use fiTQun algorithm (complete charge & time information) à enable to
extend detector fiducial volume, lead to 20% effectively statistic increases in
selecting e-like events
² Add CC1𝜋 e-like sample à increase 10% for neutrino mode e-like
² Usage of ND280 data
² Include FGD2 (water targets) to include interactions on water
² Interaction model improvements in NEUT (neutrino event
generator)
² Improve pion production model
² Include a model for multi-nucleon scattering
² Improve CCQE model by including effect of long-range correlations in nucleus

7. Far detector data samples with fit
08/12/17 ICRR Annual Review 2017 7
Reconstructed Energy (GeV)ν
0 0.2 0.4 0.6 0.8 1 1.2NumberofEvents
0
2
4
6
8
10
12
eν→µν
eν→µν
NC
intrinsiceν/eν
intrinsicµν
intrinsicµν
T2K Run1-8 PreliminaryFinal systematics pending
Reconstructed Energy (GeV)ν
0 0.2 0.4 0.6 0.8 1 1.2
NumberofEvents
0
0.5
1
1.5
2
2.5
3
3.5 eν→µν
eν→µν
NC
intrinsiceν/eν
intrinsicµν
intrinsicµν
T2K Run1-8 PreliminaryFinal systematics pending
Reconstructed Energy (GeV)ν
0 0.2 0.4 0.6 0.8 1 1.2
NumberofEvents
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
eν→µν
eν→µν
NC
intrinsiceν/eν
intrinsicµν
intrinsicµν
T2K Run1-8 PreliminaryFinal systematics pending
Reconstructed Energy (GeV)ν
0 0.5 1 1.5 2 2.5 3
NumberofEvents
0
5
10
15
20
25
30
eν→µν
eν→µν
NC
intrinsiceν/eν
intrinsicµν
intrinsicµν
T2K Run1-8 PreliminaryFinal systematics pending
Reconstructed Energy (GeV)ν
0 0.5 1 1.5 2 2.5 3
NumberofEvents
0
2
4
6
8
10
12
eν→µν
eν→µν
NC
intrinsiceν/eν
intrinsicµν
intrinsicµν
T2K Run1-8 PreliminaryFinal systematics pending
Neutrino mode
Anti-neutrino mode
Appearance channelDisappearance channel
CCQE 1 𝜇-like ring CCQE 1 e-like ring CC1𝜋 1 e-like ring
CCQE 1 𝜇-like ring CCQE 1 e-like ring

8. Atmospheric parameter constraint
08/12/17 ICRR Annual Review 2017 8
)23θ(2
sin
0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7
)-4c2
|(eV32
2
m∆|
2.3
2.35
2.4
2.45
2.5
2.55
2.6
2.65
2.7
3−
10×
Normal - 68CL
Normal - 90CL
Inverted - 68CL
Inverted - 90CL
Best fit
T2K Run1-8 PreliminaryFinal systematics pending
² Data is fitted separately for normal
and inverted hierarchy Data fit
Final
systematic
error
pending
(Study of ND data-driven
variation show effect on
atmospheric parameters)
² Pending final systematic error, results
maybe updated in future

9. Mixing angle 𝜃13 & 𝛿CP
08/12/17 ICRR Annual Review 2017 9
)13θ(2
sin
10 15 20 25 30 35 40 45 50
3−
10×
(Radians)CPδ
3−
2−
1−
0
1
2
3 Normal - 68CL
Normal - 90CL
Inverted - 68CL
Inverted - 90CL
Best fit
PDG 2016
T2K Run1-8 PreliminaryFinal systematics pending
)13θ(2
sin
15 20 25 30 35
3−
10×
(Radians)CPδ
3−
2−
1−
0
1
2
3 Normal - 68CL
Normal - 90CL
Inverted - 68CL
Inverted - 90CL
Best fit
T2K Run1-8 PreliminaryFinal systematics pending
² T2K sin2 𝜃13 measurement is
consistent with PDG 2016 average
T2K value:
PDG 2016:
² Include the reactor constraint on 𝜃13
improves constraint on 𝛿CP
sin2
✓13 = 0.0277+0.0054
0.0047 (NH)
sin2
✓13 = 0.0210 ± 0.0011
w/ reactor constraint

10. 𝛿CP measurement
08/12/17 ICRR Annual Review 2017 10
(rad)CPδ
3− 2− 1− 0 1 2 3
ln(L)∆-2
0
5
10
15
20
25
30
Normal
Inverted
T2K Run1-8 PreliminaryFinal systematics pending
² 1𝝈 CL. confidence interval
Normal Hierarchy [-2.49, -1.23] rad.
² 2 𝝈 CL. confidence interval
Normal hierarchy [-2.91, -0.60] rad.
Inverted hierarchy [-1.54, -1.19] rad.
à CP conserving values (0, 𝜋) fall outside
of the 2𝝈 CL. confidence/credible interval
2𝝈 CL. intervals
(rad.)CPδ
3− 2− 1− 0 1 2 3
Posteriorprobabilitydensity
0
0.1
0.2
0.3
0.4
0.5
0.6 95.4% Credible Interval
90% Credible Interval
68% Credible Interval
T2K Run 1-8 preliminary
Frequentist
Bayesian
Reconstructed Energy (GeV)ν
0 0.2 0.4 0.6 0.8 1 1.2
NumberofEvents
4−
2−
0
2
4
6
8
10
12
14
16
T2K Run1-8 Preliminary
= 0CP
δ
Data

11. Future plans
08/12/17 ICRR Annual Review 2017 11
Short-term
² Requested 9x1020 POT before summer
2018 (mainly in anti-neutrino mode)
² Super-K tank open from June 2018 to
repair the leak, install a new water pipe
and replace dead PMT
Long-term
² Upgrade MR power supplies to increase
beam power
² T2K-II
² Proposal to collect 20 x 1021 by JFY2026
² Neutrino beamline upgrade & analysis
improvement to effectively add 50% statistics
² ND280 upgrade is proposed and formally
approved by T2K
JFY
2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027
MRBeamPower[kW]
0
200
400
600
800
1000
1200
1400
POT]21
IntegratedDeliveredProtons[10
0
5
10
15
20
25
30
35
40
45
POT]21
.[10July)−(Oct.DeliveredProtons/Period
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
MR Power Supply upgrade
T2K-II Protons-On-Target Request
)°(CP
δTrue
200− 100− 0 100 200
=0CPδtoexcludesin2
χ∆
0
5
10
15
20
=0.4323θ2
True sin
=0.5023θ2
True sin
=0.6023θ2
True sin
POT w/ eff. stat. & sys. improvements21
20x10
POT w/ 2016 sys. errs.21
7.8x10
90% C.L.
99% C.L.
C.L.σ3

12. Summary
08/12/17 ICRR Annual Review 2017 12
² T2K primary goal ( ) has achieved but our journey is not over.
Now is an exciting and challenging time.
² T2K is leading the effort to measure CP violation & continues to
produce high-impact results.
² T2K future plans are happening now! Physics prospects of T2K-II
and ND280 upgrades are sensational!
⌫µ ! ⌫e
⌫µ ! ⌫e

13. 1308/12/17 ICRR Annual Review 2017