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Home , T2K experiment

A brief overview of oscillaon results and future prospects

Trevor Stewart On behalf of the T2K collaboraon Rutherford Appleton Laboratory

ICNFP 2016 01/01/2015 Trevor Stewart, RAL 1 The Nobel Prize in Physics 2015 , Arthur B. McDonald

“for the discovery of neutrino oscillaons, which shows that have mass"

06/07/2016 Trevor Stewart, RAL 2 Intoducon • This talk will discuss recent neutrino oscillaon results and how they contribute to our overall understanding of the physics of neutrinos • Will present results from current experiments such as T2K, NOνA, Daya Bay, RENO, and Double • Discuss future experiments such as Hyper- Kamiokande, DUNE, and JUNO • If I do not menon your favourite experiment then please forgive me, it is for the sake of brevity

01/01/2015 Trevor Stewart, RAL 3 Two-flavour neutrino oscillaons

⌫ cos✓ sin✓ ⌫ • e = 1 Two sets of eigenstates for ⌫µ sin✓ cos✓ ⌫2 neutrinos ✓ ◆ ✓ ◆✓ 2 ◆ - Flavour states which 2 2 ⎛ Δm L ⎞ P(ν →ν ) = sin (2θ )sin ⎜ ⎟ interact µ e ⎜ 4E ⎟ m2 = m2 m2 ⎝ ⎠ - Mass states which 2 1 propagate ⌫µ ⌫1, ⌫2 ⌫µ or ⌫e

• Measure • Result probabilies – Mixing angle(s) – Disappearance – Mass differences – Appearance 01/01/2015 Trevor Stewart, RAL 4 The Pontecorvo-Maki-Nakagawa-Sakata (PMNS) mixing matrix

⌫e ⌫1 • Unfortunately things are not as ⌫ = U ⌫ 0 µ1 0 21 simple as the 2-flavour mixing ⌫⌧ ⌫3 shown on the previous slide @ A @ A • 3-flavour mixing Flavour eigenstates Mass eigenstates - Three independent mixing (coupling to the W, Z) (definite masses) angles and CP violang phase

i 10 0 cos✓13 0 sin✓13e cos✓12 sin✓12 0 10 0 U = 0 cos✓ sin✓ 010 sin✓ cos✓ 0 0 ei2 0 0 23 23 1 0 1 0 12 12 1 0 1 0 sin✓ cos✓ sin✓ ei 0 cos✓ 00100ei3 23 23 13 13 @ A @ A @ A @ A Appearance Neutrino-less Reactor measurements Atmospheric and long- measurements double beta baseline disappearance disappearance decay measurements measurements

01/01/2015 Trevor Stewart, RAL 5 Open quesons o • Is θ23 = 45 ? Which octant? • The large value of θ13 allows for large CP-violaon effects

- what is δCP? • Oscillaon experiments can only probe the squared differences between the neutrino masses:

- m2 > m1 - Sll unknown if m3 > m2 m3 > m2: normal hierarchy m2 > m3: inverted hierarchy • Precision tests of the PMNS framework are sll needed

06/07/2016 Trevor Stewart, RAL 6 Accelerator measurements

06/07/2016 Trevor Stewart, RAL 7 Oscillaon probabilies

νμ disappearance m2 L P (⌫ ⌫ ) 1 (cos4✓ sin22✓ +sin2✓ sin22✓ )sin2 31 µ ! µ ⇡ 13 23 23 13 4E

νe appearance 2 2 2 2 2 2 m31L sin2✓12sin2✓23 2 m21L 2 2 m31L P (⌫µ ⌫e) sin 2✓13sin ✓23sin sin sin 2✓13sin sinCP ! ⇡ 4E 2sin✓13 4E 4E

• νμ disappearance: Sensive to θ23 and o o its octant (θ23 > 45 ? or θ23 < 45 ) PDG 2014 • ν appearance: Sensive to θ and δ e 13 CP o θ23 = 45.8 ± 3.2 • Dependence on L/E (distance o θ12 = 33.4 ± 0.85 travelled/Energy of neutrino) o θ13 = 8.88 ± 0.39 2 -5 2 Δm 21 = (7.53 ± 0.18) x 10 eV 2 -3 2 |Δm 32| = (2.44 ± 0.06) x 10 eV

06/07/2016 Trevor Stewart, RAL 8 The T2K experiment Started collecng data in 2010

Increasing beam power: currently stable running achieved at 420 kW

νe, νμ νμ, Long-baseline neutrino ντ oscillaon experiment

Primarily studies νμ ND280 +INGRID disappearance and

νμèνe appearance to measure 2 θ13, θ23 (and its octant), Δm 32 and δcp

06/07/2016 Trevor Stewart, RAL 9 NOνA experiment

• Like T2K, a long- baseline neutrino oscillaon experiment – Similaries and differences described on next slide • Starng taking physics data in 2014 • Funconally idencal near and far detectors

01/01/2015 Trevor Stewart, RAL 10 T2K and NOνA

Off-axis beam allows one to have a larger flux at the energy where oscillaons to neutrinos are expected to be at maximum

Narrowness of the beam aids in rejecng π0 background and νe contaminaon of the νμ beam

T2K NOνA

01/01/2015 Trevor Stewart, RAL 11 T2K beam

2011 2012 2013 2014 2015 2016

27 May 2016 !-mode POT: 7.57×1020 (50.14%) POT total: 1.510×1021 !-mode POT: 7.53×1020 (49.86%) • First data useable for physics analysis in 2010 • Steady rise in beam power from • Run 1 ≈ 50 kW • Run 7 420 kW • Total of 15.1 x 1020 POT ( on target) accumulated by 27 May 2016 06/07/2016 Trevor Stewart, RAL 12 T2K beam

See Andrea Longhin2011 2012 talk 2013Recent results 2014 2015 2016

from the T2K experiment 27 May 2016 !-mode POT: 7.57×1020 (50.14%) th POT total: 1.510×1021 !-mode POT: 7.53×1020 (49.86%) • First data useable for physics analysis in 2010 July 13 @ 09:00 for more details • Steady rise in beam power from • Run 1 ≈ 50 kW • Run 7 420 kW • Total of 15.1 x 1020 POT (protons on target) accumulated by 27 May 2016 06/07/2016 Trevor Stewart, RAL 13 Where are we?: T2K 80 T2K Run17b preliminary Unoscillated 14 T2K Run17b preliminary Unoscillated Prediction Prediction 70 Events Best-Fit Events 12 Best-Fit 60 10 Data ⌫ Data 50 e New results, presented 8 40 ⌫ 6 30 µ 2 days ago at Neutrino 20 4 10 2 2016 0 0 o 4 -1 o 150 200 400 600 800 1000 1200 1400 103 1 Rati Rati 10 2 1 5 0 0 10-1 2×10-1 1 2 3 4 5 6 7 8 0 200 400 600 800 1000 1200 1400 Reconstructed Energy [GeV] Reconstructed Momentum [MeV/c] neutrino disappearance 3.5 T2K Run17b preliminary Unoscillated T2K Run17b preliminary Unoscillated 25 Prediction 3 Prediction Events Best-Fit Events Best-Fit observed in both 20 2.5 Data Data 2 ⌫¯ 15 e neutrino and an- ⌫¯ 1.5 10 µ 1 neutrino beams 5 0.5 0 0 o 4 o -1 80 200 400 600 800 1000 1200 1400 103 1

Rati Rati 6 2 4 1 2 An- 0 0 10-1 2×10-1 1 2 3 4 5 6 7 8 0 200 400 600 800 1000 1200 1400 Reconstructed Energy [MeV] Reconstructed Momentum [MeV/c] appearance (4 events) How about measurements of the oscillaon parameters?

06/07/2016 Trevor Stewart, RAL 14 Oscillaon measurements: T2K 3 25 T2K Run1-7b preliminary T2K Run1-7b preliminary -2lnL 2 68%CL (-2ln L = 2.3) 20

(radians) Normal Hierarchy 90%CL (-2ln Lcrit = 4.61)

CP T2K only crit δ 1 Best-fit Inverted Hierarchy PDG 2015 15 0 Normal Hierarchy 10 -1 Inverted Hierarchy -2 5 Fixed Mass Hierarchy -3 0 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 -3 -2 -1 0 1 2 3 2 (radians) sin θ13 δCP

3 T2K Run1-7b preliminary • δCP vs. θ13 (le) 2 T2K + reactor

(radians) 68%CL (-2ln L = 2.3) • Data @ 90% CL

CP θ13 crit δ 1 90%CL (-2ln L = 4.61) crit - δ = [-3.02, -0.49] for NH Best-fit CP 0 - δCP = [-1.87, -0.98] for IH Normal Hierarchy -1 Inverted Hierarchy -2 Fixed Mass Hierarchy -3 0.0160.018 0.02 0.0220.0240.0260.028 0.03 0.0320.0340.036 sin2 θ 06/07/2016 13 Trevor Stewart, RAL 15 Oscillaon measurements: T2K

) 3.6 4

/c 68%CL 2 3.4 90%CL Normal Hierarchy

eV 3.2 T2K best-fit • Results consistent with -3 3 maximal mixing | (10 2 32 2.8 • 2016: m Δ | 2.6 - A new joint analysis using 2.4 neutrino and an- 2.2 2 IceCube Super-K neutrino disappearance 1.8 T2K Run1-7b preliminary NOvA (2015) MINOS+ and appearance 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 measurements (le) sin2 θ 23

01/01/2015 Trevor Stewart, RAL 16 NuMI beam

• Data taken 6th Feb. 2014 to 2 May 2016 - 6.05 x 1020 POT

• NuMI beamline provides neutrino beams to a number of different experiments • MINOS, MicroBooNE, ICARUS, SBND, MINERvA • Connuously increasing beam power - Currently operang at design power of 700 kW

01/01/2015 Trevor Stewart, RAL 17 Oscillaon measurements: NOνA νμ disappearance

ν appearance • New results, presented 2 days ago at Neutrino e 2016

• νμ disappearance - Results already in good agreement with other oscillaon experiments - Maximal mixing excluded at 2.5σ

• νe appearance - 33 events observed - >8σ significance 01/01/2015 Trevor Stewart, RAL 18 Reactor measurements

01/01/2015 Trevor Stewart, RAL 19 Reactor experiments

• Nuclear reactors provide very intense sources of with a well understood spectrum ⌫¯e - @ 3 GW – 6 x 1020 ⌫¯e /s - Spectrum peaks at 3.7 MeV (low energy compared to accelerator experiments) - Energy not sufficient to create νμ or ντ • No appearance measurements, only νe disappearance - Not sensive to δCP • Both reactor and accelerator measurements needed

Look for small rate deviaon from 1/r2 measured at near and far detectors

Will discuss results from 3 reactor neutrino experiments: RENO DAYA Bay

01/01/2015 Trevor Stewart, RAL 20 Measuring θ13

m2 L m2 L P (¯⌫ ⌫¯ ) 1 sin22✓ sin2 ee cos4✓ sin22✓ sin2 21 e ! e ⇡ 13 4E 13 12 4E m2 = cos2✓ m2 +sin2✓ m2 | ee| 12| 31| 12| 32|

Reactor oscillaon experiments provide a straighorward way to measure θ13 with no dependence on δCP or maer effects

• θ13 measurements affect θ12, θ23, and δCP measurements at long-baseline accelerator experiments - Thus, the need to measure it as precisely as possible at reactor experiments

01/01/2015 Trevor Stewart, RAL 21 Current experiments

Daya Bay @ Daya Bay, China

Double Chooz @ Chooz, France

RENO @ Yonggwang, Korea

01/01/2015 Trevor Stewart, RAL 22 θ13 Double Chooz Moriond 2016

2 2 Best-fit value for sin 2θ13 = 0.111 ± 0.018 (stat. + syst.) χ /dof = 128.8/120

01/01/2015 Trevor Stewart, RAL 23 θ RENO 13 PRL 116, 211801 (2016)

2 Best-fit value for sin 2θ13 = 0.082 ± 0.009 (stat.) + 0.006 (syst.)

01/01/2015 Trevor Stewart, RAL 24 θ Daya Bay 13 PRL 115, 111802 (2015)

2 Best-fit value for sin 2θ13 = 0.084 ± 0.005

01/01/2015 Trevor Stewart, RAL 25 Reactor neutrino disappearance L/E Daya Bay PRL 115, 111802 (2015) RENO PRL 116, 211801 (2016)

m2 L m2 L P (¯⌫ ⌫¯ ) 1 sin22✓ sin2 ee cos4✓ sin22✓ sin2 21 e ! e ⇡ 13 4E 13 12 4E Recall from slide 21: L/E dependence to disappearance probability

Detectors at a mulple baselines, a variety of neutrino energies

Good agreement between data and predicon

06/07/2016 Trevor Stewart, RAL 26 Future prospects

01/01/2015 Trevor Stewart, RAL 27 T2K and “T2K-II”

• T2K has accumulated 1.510 x 1021 POT as of May 27th 2016 • Approved T2K stascs 7.8 x 1021 POT – 1st stage of J-PARC main ring power supply upgrade approved – > 1 MW beam power (currently 420 kW)

• Hyper-Kamiokande and DUNE are expected to come online around 2026 – “T2K-II” extension of run unl JF2026 to accumulate 20 x 1021 POT – Will require accelerator and beamline upgrades to allow operaon at 1.3 MW – Increase horn current from 250 kA to 320 kA • Increased neutrino flux • Reducon of wrong-sign background

01/01/2015 Trevor Stewart, RAL 28 T2K-II physics potenal

Mass hierarchy known Mass hierarchy unknown

• 3σ sensivity to δCP (% coverage) - Stascal uncertainty only (43%) - Current systemac uncertaines (20.5%) - Improve systemac uncertaines to 4% (36.1%) • θ23 resoluon of ≈1.7% 01/01/2015 Trevor Stewart, RAL 29 Hyper-Kamiokande

Super-Kamiokande 50 kT Water Cherenkov detector Hyper-Kamiokande 520 kT Water Cherenkov detector Will ulize the same baseline as T2K/T2K-II and accelerator infrastructure based in Tokai at J-PARC

The far detector, Hyper-Kamiokande, will have a far greater water volume. Much larger stascs!

Begin operaon in 2026 01/01/2015 Trevor Stewart, RAL 30 Hyper-Kamiokande physics potenal

2 • Precision Δm 23/θ23 measurements - ~1.4 x 10-5 eV2 - Mass hierarchy sensivity with reactor constraint • Sensive to CP violaon - 3σ for 78% of δCP - 5σ for 62% of δCP o - ≈7 precision on δCP measurement possible Normal mass hierarchy 12 σ

10 2 sin θ23=0.50 8

6 5σ 4 2 3σ sin ✓23 =0.45 2

0 -150 -100 -50 0 50 100 150

δCP 06/07/2016 Trevor Stewart, RAL 31 DUNE

• 1300 km baseline • A large 40 kT high resoluon far detector • A near detector to constrain the event rate at the far detector

01/01/2015 Trevor Stewart, RAL 32 DUNE physics potenal • Will be able to measure δCP to 5σ across most of the angular range - 6-10o resoluon aer 10 years of running - Begin operaon with 20 kT far detector in 2024 40 kT and design beam power in 2026

01/01/2015 Trevor Stewart, RAL 33 JUNO

• Being built in Kaiping, Jiangmen, China • Liquid scinllator volume: 20x that of Daya Bay • Light yield: 5x that of Daya Bay

• More stascs and beer resoluon 01/01/2015 Trevor Stewart, RAL 34 RENO-50 Near Courtesy by YoshitaroTakaesu Detector (Tokyo) • Wide ranging physics goals - Mass hierarchy - Oscillaon parameters - Supernova neutrinos - Geo-neutrinos Far - Solar neutrinos Detector - Sterile neutrinos - Detecon of J-PARC beam neutrinos • Same beam as T2K/HK • Proposed date to come online RENO-50 2022 18 kton LS Detector ~47 km from YG reactors Mt. Guemseong (450 m) ~900 m.w.e. overburden

06/07/2016 Trevor Stewart, RAL 35 Conclusions

• Neutrino oscillaon measurements have provided a number of surprising discoveries over the last 2 decades – The three-neutrino mixing scheme has been established, implying physics beyond the standard model • Most of the oscillaon parameters have been measured, but … • … there sll exist open quesons

– mass hierarchy and value of δCP – The interplay between accelerator and reactor based experiments is crucial • Major efforts are currently underway to answer these open quesons with both exisng and future experiments

01/01/2015 Trevor Stewart, RAL 36