A brief overview of neutrino oscilla on results and future prospects
Trevor Stewart On behalf of the T2K collabora on Rutherford Appleton Laboratory
ICNFP 2016 01/01/2015 Trevor Stewart, RAL 1 The Nobel Prize in Physics 2015 Takaaki Kajita, Arthur B. McDonald
“for the discovery of neutrino oscilla ons, which shows that neutrinos have mass"
06/07/2016 Trevor Stewart, RAL 2 Intoduc on • This talk will discuss recent neutrino oscilla on 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 Chooz • Discuss future experiments such as Hyper- Kamiokande, DUNE, and JUNO • If I do not men on your favourite experiment then please forgive me, it is for the sake of brevity
01/01/2015 Trevor Stewart, RAL 3 Two-flavour neutrino oscilla ons
⌫ 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 probabili es – 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 viola ng 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 ei 2 0 0 23 23 1 0 1 0 12 12 1 0 1 0 sin✓ cos✓ sin✓ ei 0 cos✓ 00100ei 3 23 23 13 13 @ A @ A @ A @ A Appearance Solar neutrino Neutrino-less Reactor measurements Atmospheric and long- measurements double beta baseline disappearance disappearance decay measurements measurements
01/01/2015 Trevor Stewart, RAL 5 Open ques ons o • Is θ23 = 45 ? Which octant? • The large value of θ13 allows for large CP-viola on effects
- what is δCP? • Oscilla on experiments can only probe the squared differences between the neutrino masses:
- m2 > m1 - S ll unknown if m3 > m2 m3 > m2: normal hierarchy m2 > m3: inverted hierarchy • Precision tests of the PMNS framework are s ll needed
06/07/2016 Trevor Stewart, RAL 6 Accelerator measurements
06/07/2016 Trevor Stewart, RAL 7 Oscilla on probabili es
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 sin CP ! ⇡ 4E 2sin✓13 4E 4E
• νμ disappearance: Sensi ve to θ23 and o o its octant (θ23 > 45 ? or θ23 < 45 ) PDG 2014 • ν appearance: Sensi ve 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 collec ng data in 2010
Increasing beam power: currently stable running achieved at 420 kW
νe, νμ νμ, Long-baseline neutrino ντ oscilla on 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 oscilla on experiment – Similari es and differences described on next slide • Star ng taking physics data in 2014 • Func onally iden cal 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 oscilla ons to electron neutrinos are expected to be at maximum
Narrowness of the beam aids in rejec ng π0 background and νe contamina on 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 (protons 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 Run1 7b preliminary Unoscillated 14 T2K Run1 7b 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] Muon neutrino disappearance 3.5 T2K Run1 7b preliminary Unoscillated T2K Run1 7b 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 -electron neutrino 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 oscilla on parameters?
06/07/2016 Trevor Stewart, RAL 14 Oscilla on 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 Oscilla on 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 • Con nuously increasing beam power - Currently opera ng at design power of 700 kW
01/01/2015 Trevor Stewart, RAL 17 Oscilla on 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 oscilla on 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 sensi ve to δCP • Both reactor and accelerator measurements needed
Look for small rate devia on from 1/r2 measured at near and far detectors
Will discuss results from 3 reactor neutrino experiments: Double Chooz RENO DAYA Bay
01/01/2015 Trevor Stewart, RAL 20 Measuring θ13