Recent T2K Neutrino Oscillation Results Artur Sztuc - PowerPoint PPT Presentation

Recent T2K Neutrino Oscillation Results Artur Sztuc a.sztuc16@imperial.ac.uk On behalf of the T2K collaboration TAUP 2019

Neutrino Mass Mixing Normal Hierarchy (NH) Inverted Hierarchy (IH) ν 3 • Flavour eigenstates; ν e , ν µ and ν τ (interact) • Mass eigenstates; ν 1 , ν 2 ν 2 and ν 3 (propagate) ν 1       � ν e � s 13 e − i δ CP � ν 1 � 1 0 0 0 0 c 13 c 12 s 12 = ν µ ν 2 0 c 23 s 23 0 1 0 − s 12 c 12 0       ν τ ν 3 0 − s 13 e δ CP 0 0 1 − s 23 c 23 0 c 13 � �� � � �� � � �� � atmospheric, beam solar, reactor reactor, beam Super-K, T2K, NO ν A, Double Super-K, s ij = sin θ ij IceCube, T2K, Chooz, Daya Bay, KamLAND, c ij = cos θ ij NO ν A, Opera RENO SNO Artur Sztuc TAUP, Sep 2019 2

The T2K experiment • Around 500 people from 68 institutions, 12 countries • ∼ 0.6 GeV narrow beam from J-PARC ( ν and ¯ ν mode) • Near detector; ND280, 280 m from beam target, measures unoscillated spectrum • Far detector; Super-Kamiokande, 295 km from the ν source, measures oscillated spectrum Artur Sztuc TAUP, Sep 2019 3

Long baseline oscillations (@T2K) ν µ disappearance ν e appearance Number of events per bin Number of events per bin 20 300 Unoscillated Prediction Unoscillated Prediction 18 Oscillated with Reactor Constraint Oscillated with Reactor Constraint Oscillated without Reactor Constraint 250 Oscillated without Reactor Constraint 16 Data Data 14 T2K Run 1-9d Preliminary T2K Run 1-9d Preliminary 200 12 10 150 8 100 6 4 50 2 0 0 Ratio 20 2 Ratio 10 1 0 0 0 0.2 0.4 0.6 0.8 1 1.2 0 1 2 3 4 5 6 7 Reconstructed Neutrino Energy (GeV) Reconstructed Neutrino Energy (GeV) Location of the dip: | ∆ m 2 Magnitude of the peak; 32 | sin 2 ( θ 23 ), sin 2 ( θ 13 ), δ CP (does not depend on the sign) Depth of the dip: sin 2 ( θ 23 ) Small dependence on the sign of ∆ m 2 32 Channel for CP violation detection Difficult to separate θ 23 > 45 and θ 23 < 45 32 | , sin 2 θ 23 , sin 2 θ 13 First-order sensitivity: | ∆ m 2 32 , sin 2 θ 23 octant, δ CP Second-order sensitivity: sign of ∆ m 2 Artur Sztuc TAUP, Sep 2019 4

The T2K neutrino beam 1 ) µ ν θ 2 → sin 2 = 1.0 0.5 23 2 θ µ sin 2 = 0.1 ν 13 P( ∆ × -3 2 2 m = 2.4 10 eV 32 0 1 2 3 0.1 δ δ ) NH, = 0 IH, = 0 e CP CP ν δ π δ π NH, = /2 IH, = /2 CP CP → 0.05 µ ν P( 0 1 2 3 ° 1 OA 0.0 𝝃 ° OA 2.0 (A.U.) The latest result includes 𝜉̅ ° OA 2.5 combined run 1–9 data 295km 0.5 • ν µ : 1 . 51 × 10 21 POT µ ν Φ ν µ : 1 . 65 × 10 21 POT • ¯ 0 0 1 2 3 E (GeV) ν (POT; Protons on target) Off-axis beam angle tuned for maximal ν µ disappearance Beam operating near 500kW Artur Sztuc TAUP, Sep 2019 5

T2K near detectors ND280 • Off-axis, 280 m from beam target • Measures unoscillated ν spectrum • Neutrino cross-section measurements (T2K cross-sections results talk) INGRID • On-axis, 280 m from beam target • Measures beam direction and stability • Also contributes to cross-sections • Different flux spectrum Artur Sztuc TAUP, Sep 2019 6

Analysis strategy ND280 INGRID/ ND280 External Data Beam detector Cross- monitor model section NA61 data data SHINE Data Cross- section model Flux model Oscillation Fit Super-K Super-K data detector model Oscillation parameters Artur Sztuc TAUP, Sep 2019 7

ND280 Data selection ND280 data constrains the neutrino flux and cross-section systematics at Super-K Data samples for two FGD targets (CH and H 2 O); • 3 × 2 samples for ν beam mode • ν µ CC0 π (primary in the analysis) • ν µ CC1 π (shown on right) • CCOther • 4 × 2 samples for ¯ ν beam mode • ¯ ν µ CC1Track • ¯ ν µ CCNTrack • ν µ CC1Track • ν µ CCNTrack Two Fine Grid Detectors (FGD), event display shows FGD1 producing µ + and π − H 2 O samples constrain water interactions at Super-K Data are binned in outgoing µ momentum and angle Artur Sztuc TAUP, Sep 2019 8

ND280 data fit effect Prefit CC0 π Postfit CC0 π ν ν -mode -mode Events/(100 MeV/c) Events/(100 MeV/c) 2500 2500 Data Data ν ν CCQE CCQE 2000 ν 2000 ν CC 2p-2h CC 2p-2h ν π ν π CC Res 1 CC Res 1 1500 1500 ν π ν π CC Coh 1 CC Coh 1 ν ν CC Other CC Other 1000 1000 ν ν NC modes NC modes ν ν modes modes 500 500 Data / Sim. 0 Data / Sim. 0 1.2 1.2 1.1 1.1 1.0 1.0 0.9 0.9 0.8 0.8 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 Reconstructed muon momentum (MeV/c) Reconstructed muon momentum (MeV/c) PRELIMINARY PRELIMINARY • The prediction agrees much better with the data after the ND280 fit • This is true for all the data samples Artur Sztuc TAUP, Sep 2019 9

ND280 data fit effect ND280 ν µ beam flux ND280 FHC Flux ν µ 1.3 1.2 1.1 1.0 0.9 • Constraining both flux and 0.8 Prior to ND280 constraint 0.7 cross-section systematics After ND280 constraint 0.6 0.5 (See T2K cross-sections results talk -1 10 1 10 Neutrino Energy (GeV) by Callum Wilkinson) Super-K event rates systematic errors • The effect is large Super-K Without With ← Systematic errors on Super-K sample ND280 ND280 event rates reduced ν -beam 1-Ring- µ 14.6% 5.1% ν -beam 1-Ring-e 16.9% 8.8% ν -beam 1-Ring- µ ¯ 12.5% 4.5% ν -beam 1-Ring-e ¯ 14.4% 7.1% Artur Sztuc TAUP, Sep 2019 10

Super-K Data T2K Run 1-9 preliminary Antineutrino mode 1Re candidates 24 ν -beam 1-Ring-e ¯ 22 20 18 θ 16 2 sin = 0.50 , 0.45 , 0.55 23 ∆ × -3 2 2 4 m = 2.45 10 eV /c 32 ∆ 2 × -3 4 14 m = -2.43 10 eV 2 /c 31 δ π = CP δ π 12 = + /2 CP δ = 0 CP δ π 10 = - /2 CP Data (stat. errors only) 8 30 40 50 60 70 80 90 100 110 Neutrino mode 1Re candidates Sample δ CP = − π/ 2 δ CP = 0 δ CP = π/ 2 δ CP = π Observed ν -beam 1-Ring- µ 272.4 272.0 272.4 272.8 243 ¯ ν -beam 1-Ring- µ 139.5 139.2 139.5 139.9 140 ν -beam 1-Ring-e 74.4 62.2 50.6 62.7 75 ν -beam 1-Ring-e ¯ 17.1 19.4 21.7 19.3 15 ν -beam 1-Ring-e 7.0 6.1 4.9 5.9 15 P-value + π + ∼ 0.07 sin 2 θ 13 =0.0212, sin 2 θ 23 =0.528, ∆ m 2 32 =2.51 × 10 − 3 , rest fixed to 2018 PDG values Artur Sztuc TAUP, Sep 2019 11

Appearance results NH Both Hierarches IH • T2K excludes CP conservation at 2 σ • Best-fit δ CP , marginalized over both MH, is -1.74 rad • Constraints tighter than in the expected sensitivity • Best-fit sin 2 ( θ 13 ) = 0 . 0214 Artur Sztuc TAUP, Sep 2019 12

Disappearance results Both Hierarchies NH • Bayes factor of 8.0 for NH/IH • Considered “significant” by the Jeffrey’s scale • NH 8 times more probable than IH • Best-fit sin 2 ( θ 23 ) = 0 . 537 • Best-fit ∆ m 2 32 = 2 . 46 × 10 − 3 Artur Sztuc TAUP, Sep 2019 13

Conclusions • CP conserving values ( δ CP = 0 , π ) comfortably excluded at 2 σ • Best-fit δ CP value: -1.74 rad • Data prefers Normal Hierarchy ( ∼ 89%) • Preference for the upper octant of sin 2 θ 23 ( ∼ 80%) • More talks and posters from T2K! Artur Sztuc TAUP, Sep 2019 14

BACKUPS Artur Sztuc TAUP, Sep 2019 15

Beam flux Neutrino Mode Flux at ND280 Antineutrino Mode Flux at ND280 p.o.t) p.o.t) 12 10 12 21 10 21 ν ν ν ν /50MeV/10 /50MeV/10 µ µ e e ν ν ν ν µ µ e e 11 10 11 10 2 2 Flux (/cm Flux (/cm Beam flux composition at 10 10 ND280 10 10 9 10 9 10 8 10 0 2 4 6 8 10 0 2 4 6 8 10 E (GeV) E (GeV) ν ν Neutrino Mode Flux at the far detector Antineutrino Mode Flux at the far detector p.o.t) p.o.t) 6 10 6 10 21 21 ν ν ν ν /50MeV/10 /50MeV/10 µ µ e e ν ν ν ν 5 µ 10 µ e e 5 10 Beam flux composition at 2 2 Flux (/cm Flux (/cm 4 10 Super-K 10 4 3 10 3 10 2 10 0 2 4 6 8 10 0 2 4 6 8 10 E (GeV) E (GeV) ν ν Artur Sztuc TAUP, Sep 2019 16

Neutrino interactions Charged Current Quasi Charged Current Resonant Charged Current Deep Elastic (CCQE) Inelastic Scattering (CCDIS) Pion (CCRES) ν l − l ν l − ν l − l l π + W W W u N d N d u d d u p u u ++ u p p Δ n d d hadrons u u u u u • CCQE dominant interaction mode for T2K • Interactions with nucleon inside a nucleus • Nuclear model dependent • Nuclear effects can bias interaction mode and energy reconstruction • Interaction and Nuclear models tuned to external data Artur Sztuc TAUP, Sep 2019 17