The T2K experiment Results and Perspectives. PPC2017 Corpus Christi Mai 2017 Michel Gonin On behalf of the T2K collaboration

Transcription

1 The T2K experiment Results and Perspectives PPC2017 Corpus Christi Mai 2017 Michel Gonin On behalf of the T2K collaboration 1

2 Overview Neutrino oscillations The T2K off-axis experiment Oscillation results T2K perspectives Summary 2

3 Neutrino oscillations Production Neutrino Mixing μ + e - Detection Interaction : flavor states Propagation : mass states Interaction : flavor states Still missing 1) Mass ordering, m 3 > m 2 and m 1? 2) CP Phase, δ = 0? 3) Precision on mixing angles 3

4 Neutrino oscillations J.I. NNN2016 4

5 Neutrino oscillations 5

6 The T2K off-axis experiment ~ 500 members, 62 Institutes, 11 countries 6

7 The T2K off-axis experiment Off-axis beam (muon neutrinos) with 295 km baseline 7

8 The T2K off-axis experiment Pure μ and μ beams Easy to switch from neutrino beams to antineutrino beams (horn polarities) Narrow-band beam peaked around 600 MeV (maximum oscillation) Reduced intrinsic e contamination 8

9 The T2K off-axis experiment Neutrino beam Antineutrino beam The two modes are not equivalent in terms of signal and background Wrong sign component contaminating the beam 9

10 The T2K off-axis experiment 0 Iron and scintillators tracking calorimetry Counting muon neutrinos Monitoring beam direction Monitoring beam stability Constraint systematic errors 2.5, Magnet 0.2 T In the direction of SK detector Scintillator and water targets Good tracking capabilities Cross-section measurements Constraint systematic errors Near 280 meters 10

11 Oscillation results The data set Presented data μ mode : 7.57 x protons on target μ mode : 7.53 x protons on target (About 19% of the expected T2K total data taking) Beam power reaches 450 KW (design power ~ 750 KW) 11

12 INGRID detector (on-axis) Stability monitoring Intensity Directions 12

13 T2K Systematic errors Oscillation results ND280 off-axis 2.5 measurements reduce significantly T2K systematic uncertainties Beam mode Sample type w/o ND280 w/ ND280 ND280 data constrains flux and cross-section errors propagated to the SK detector Wrong sign effects in the antineutrino mode constraint also by ND280 data An overall reduction of 50% for T2K oscillation systematic uncertainties 13

14 Oscillation results ---- New T2K analyses since summer

15 135 events Oscillation results Disappearance 66 events μ μ 32 events Appearance 4 events e e 15

16 Oscillation results Mixing angle θ 23 T2K disappearance measurements consistent with maximal mixing Compatible with other experiments Small preference for octant > π/4 T2K and NOνA prefer slightly different values 16

17 Oscillation results Mixing angle θ 23 Neutrino / Anti-Neutrino comparison No discrepancy between the two kind of measurements No sign for CPT violation Compatible with other results (Minos & Super-K) 17

18 Oscillation results Mixing angle θ 13 Change in scale Combined disappearance data T2K alone measurement consistent with reactor data Small preference for large CP violation 18

19 Oscillation results CP (matter antimatter) Violation Search δ Expected number of events (MC, Normal Hierarchy) Observed data e e More ν e appearance events than expected Fewer ν e appearance events than expected Data prefer δ = - π/2 and Normal Hierarchy CP conservation δ = 0,π is excluded at 90% CL N.H. δ = [-179,-22 ] at 90% C.L. (over 360 ) I.H δ = [-120,-42 ] at 90% C.L. 19

20 New Analysis CC non QE event : CC1π 5 events observed Available for complete T2K analysis 20

21 T2K perspectives Near Future Analysis improvements to reduce systematic errors from ~ 6% ~ 4% Sample selection improvements to increase statistics a) Super-K fiducial expansion b) Multi-ring analysis c) CC non QE events (and more) Anticipate 750 KW Beam power (~ 450 KW today) 21

22 T2K perspectives Medium term Beam Upgrades (MR power supply, upgrade MR RF, ) PHASE II Step by step Decrease bunch intervals from 2.48 sec to 1.3 sec, then 1.16 sec 450 Increase protons/bunch from to Increase horn current form 250 ka to 320 ka Proposal for T2K phase 1.3 MW Increase total delivered protons from 7.8 x (T2K) to 20.0 x

23 Medium term Near Detector 280 meters In the INGRID-ND280 pit Build new horizontal TPCs to detect high-angle tracks Build new active targets (WAGASCI detector like) Goals : better efficiency for low momenta π and p, 4π acceptance similar to Super-K and increase water target mass 23

24 Medium term Opportunities to exclude CP conservation at 3σ around 2025 with T2K phase II 24

25 Summary T2K has analyzed 15 x protons on target (accumulated 22.5 x ) which represents ~ 20% of the total approved value Combined analysis of disappearance and appearance samples in neutrino and antineutrino modes for oscillations results Disappearance measurements compatible with θ 23 maximal mixing T2K alone compatible with θ 13 measurements by reactor experiments Appearance measurement favors δ = - π/2 and Normal Hierarchy CP conservation outside our 90% confidence level interval Proposal to extend T2K to phase II with 20x10 21 P.O.T. Accelerator, beamline and detector upgrades foreseen 25