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Recent Results and Prospects

Alain Blondel

KoichiroNishikawa

(1949-2018)

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Idea of T2K was born 1999-2001 hep-ex/0106019 combining:-- existing SuperKamiokande detector (50kton W.Č., 22.5 kton fiducial)

excellent mu/e separation esp. in the sub-GeV region.

-- JAERI-KEK Japanese Proton Accelerator Research Complex (JPARC)at TOKAI including a high power, 0.75MW/30GeV Proton Synchrotronneutrino beam from pion decay π+ →µ+ νµ

-- baseline 295 km � neutrino energy for first maximum is ~650 MeVachievable by pion-decay beam at 2.5 degrees off-axis

-- designed for νµ→νe appearance search

(discovered in 2011-13);

now main aim is CPV

-- Off axis beam � narrow spectrum

peak energy given by off axis angle

-- Hadron production spectrum

measured at CERN (SHINE/NA61)

-- thin target (used, 10% on flux)

-- replica target (will be used, 5%)

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Knowledge of off-axis angle provides beam energy scale with % level precision

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The Off-Axis Near Detector monitors

event rates (vs flavour, kinematics, topology)

-+- *not* functionally identical to FD

-+- but covers full muon momentum

-+- and extracts details of interactions

--- mostly forward muons

Fine grain detector of light material

-- one FGD has 50%water layers

-- Scintillators with MPPC readout

(60’000 channels!)

-- TPC tracker in 0.2T magnetic field

UA1/NOMAD magnet donated by CERN

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A few ND280 neutrino interaction candidates

νµ

quasi-elastic candidate

single pion candidate DIS candidate

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1) Search for heavy neutrinos with the T2K near detector ND280 arXiv:1902.07598 [hep-ex].

2) Search for light sterile neutrinos with the T2K far detector Super-Kamiokande at a baseline of 295 km arXiv:1902.06529 [hep-ex].

3) Search for neutral-current induced single photon production at the ND280 near detector in T2KarXiv:1902.03848 [hep-ex].

4) T2K ND280 Upgrade - Technical Design Report arXiv:1901.03750 [physics.ins-det].

5) Search for CP Violation in Neutrino and Antineutrino Oscillations by the T2K Experiment with $2.2\times10^{21}$ Protons on Target arXiv:1807.07891 10.1103/PhysRevLett.121.171802. Phys.Rev.Lett. 121 (2018) no.17, 171802.

6) Characterization of nuclear effects in muon-neutrino scattering on hydrocarbon with a measurement of final-state kinematics and correlations in charged-current pionless interactions at T2KarXiv:1802.05078 [hep-ex]. 10.1103/PhysRevD.98.032003. Phys.Rev. D98 (2018) no.3, 032003.

7) Measurement of inclusive double-differential νµ charged-current cross section with improved acceptance in the T2K off-axis near detectorarXiv:1801.05148 [hep-ex]. 10.1103/PhysRevD.98.012004. Phys.Rev. D98 (2018) 012004.

8) First measurement of the νµ charged-current cross section on a water target without pions in the final statearXiv:1708.06771 [hep-ex]. 10.1103/PhysRevD.97.012001. Phys.Rev. D97 (2018) no.1, 012001.

10) Measurement of νµ andνµ charged current inclusive cross sections and their ratio with the T2K off-axis near detector arXiv:1706.04257 10.1103/PhysRevD.96.052001. Phys.Rev. D96 (2017) no.5, 052001.

11) Measurement of the single π0 production rate in neutral current neutrino interactions on waterarXiv:1704.07467 [hep-ex]. 10.1103/PhysRevD.97.032002. Phys.Rev. D97 (2018) no.3, 032002.

Recent T2K publications

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neutrino oscillations in T2K:

beam energy peaks at oscillation max.

magnitude of peak �sinδ, sin2 2θ13 x sin2θ23, MH

position of peak �cosδ , MH ν vsν � CP

Energy position of dip � ∆m223

depth of dip � sin2 2θ23

ν vsν � CPT

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sin δ term is CP violatingcos δ term is not.

sensitivity to δ (precision on δ measurement) is driven by sin δ term if δ is close to 0 or π � rate asymmetry νe vsνecos δ term if δ is close to ±π/2 � E shift, common to νe andνe

different systematics!

Beam delivery has been steadily improving to 500kW beam power.

Run started in 2009, interrupted by Giant Earthquake (2011) and rad incident (2013)

Recent run mostly in anti-neutrino (50% more statistics wrt neutrino 2018 results)

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Collider-style plot

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Latest T2K far detector data set

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Neutrino interaction model

Model of single muon events (CC0π) are constrained to data. This is very effective for νµ .

Additional errors remain for νe -- interplay of lepton mass, thresholds and nuclear effects

T2K flux + near detector event rates are used to predict the event rates at far detector

for any set of oscillation parameters within syst. errors

FHC (Forward Horn Current) � (h+ focus) � neutrino beam

RHC (Reverse Horn Current) � (h- focus) � anti-neutrino beam

1-ring = quasi-elastic interaction

1-ring + 1 decay electron = CC1π candidate)

Binding energy effect is constrained by νµ events at ND280, but not for νe

( binding energy)

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(due to a deficit of obsered νµ)

Full 3-family analysis

on all channels

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FUTURE PROSPECTS … LOTS!

T2K + Wagasci-Baby-MIND full detector to run in spring 2019

SK was open in 2018 starts again in March 2019

filling with Gd for improved ν vsν rejection (atmo, beam) 2020

ND280 upgrade construction (approved as CERN NP07)*) 2019-2021

JPARC power converter upgrade (double. rep rate) 2021

restart with high power (>750 kW) 2022

RF power upgrade power� 1.3 MW 2023-25

Also requires upgrades in neutrino beam infrastructure

aim at > 3 σ (expected, δ=-π/2) by start of HyperK

HyperK! seed-funded in 2019 pledged start of construction in 2020

Full data taking starts in ~2027

Also proposed:

New Intermediate Water Cherenkov detector

Second far detector in Korea

*) CERN will become member of T2K

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Accelerator-based neutrino program

in Japan: K2K � T2K � HyperK

Hyper-Kamiokande (260kt)

Super-Kamiokande(50kt)

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Near detector upgrade

motivations:

1. θ13 is large! � syst. dominate

2. Lots learned from running!

-- missing: good coverage of

large angle leptons

-- also e/γ separation and

PID within target

� replace upstream part of detector include large angle TPCs surrounding a 3D readout

fine grain scintillator detector SFGD (keep FGDs and forward TPCs)

� allows full scattering angle coverage with magnetic tracking

� SFGD target performance should allow e/γ separation

+ investigation of low momentum protons and neutrons

beautiful test beam in 2018�

Submitted to JPARC PAC and CERN SPSC

� approved (NP07 at CERN)

installation to start in 2021

to take data with upgraded beam in 2022. Alain Blondel T2K latest results and

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Comments: -- if 3.4σ NH evidence persists, T2K-II + NOvA will not be far from 5σ by 2026.

-- HK saturation at 8σ driven by assumptions on systematic errors.� strong effort and support to reduce these

-- ND280 upgrade, -- Further NA61 measurements-- New IWC near detector (E61)

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E61

1. By combination of fluxes taken at different angles,

generate a quasi-monochromatic beam

2. by the same combination of data generate the

Energy Response Function

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SPARES

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1.49 1021 POT ν + 1.63 1021 POTν

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A. Kabothnuphys18

Baysesian analysis (Markov Chain)

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