ν ν ν ν ν ν ν ν Tokai Super ‐ Kamiokande R OBERT J. W ILSON FOR THE T2K C OLLABORATION 15 D ECEMBER 2010 NNN2010 – T OYAMA , J APAN
T2K Goals � Measure last unknown mixing angle θ 13 using ν μ ➞ ν e appearance � Precise measurement of the atmospheric parameters θ 23 and Δ m 322 using ν μ ➞ ν μ disappearance R.J.Wilson/Colorado State University 4
ν e Appearance in a ν μ Beam Approximation to 3 ‐ flavor vacuum 0.16 0.08 sin 2 2 θ 13 =0.15 2 << Δ m 32 mixing with Δ m 21 2 0.14 0.07 sin 2 θ 23 =0.5 0.06 0.12 � Effectively 2 ‐ flavor mixing 0.05 0.10 � Amplitude proportional to sin 2 2 θ 13 0.04 0.08 0.03 0.06 � No evident CP phase δ dependence 0.02 0.04 � L/E chosen for oscillation maxima 0.01 0.02 0.00 0.00 Pmax ≈ 0.6 GeV 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 T2K L = 295 km ⇒ E ν E(GeV) R.J.Wilson/Colorado State University 5
Neutrino Cross Sections � Charged ‐ Current Quasi ‐ Elastic (CCQE) dominant near 1 st oscillation max � Good efficiency and energy resolution in Super ‐ K � Major Backgrounds at Super ‐ K � ν μ disappearance: CC π + is comparable size to CCQE in ν μ measurement � ν e appearance: NC π 0 , since γ and e indistinguishable in Super ‐ K � These factors guided the beam and near detector design R.J.Wilson/Colorado State University 6
Neutrino Beam Flux ν flux – 30 GeV p MR ON ‐ AXIS � On ‐ axis beam spectrum peaks ~2 GeV � Want to maximize neutrino flux at the appearance probability peak � Narrow spectrum to reduce backgrounds from higher energy processes R.J.Wilson/Colorado State University 7
Off ‐ Axis Beam Flux ν flux – 30 GeV p MR ν μ − 2 2 m m π μ = θ E ν − θ π μ 2 ( E p cos ) π π ON ‐ AXIS � Correlation between neutrino energy and direction with pion energy � Optimum for 1 st max flux and background reduction at ~2.5 ° off ‐ axis R.J.Wilson/Colorado State University 8
T2K Schematic J-PARC ND280 π ν Far Detector Off-axis detector p (SK) Target 2.5º μ (INGRID) &Horns On-axis detector Decay pipe Muon monitor Near Detector 0 m 120 m 280 m 295 km � Beam monitoring � Primary beam monitors (intensity, position, profile) � Muon monitor after the decay pipe � On ‐ axis detector (INGRID) at 280 m from the target � Beam characterization and cross section measurements � Near Detector at 280 m (ND280) 2.5 ° off ‐ axis from the beam � Far detector neutrino flavor and flux measurement � Super ‐ K 2.5 ° off ‐ axis from the beam R.J.Wilson/Colorado State University 9
Unoscillated flux at Super ‐ K MC ~0.5% ν e contamination at the peak � Almost pure ν μ beam � ν e contamination ~1% R.J.Wilson/Colorado State University 10
Oscillation Physics Sensitivity R.J.Wilson/Colorado State University 11
δ CP Dependence 3 ‐ flavor mixing in vacuum (matter effect is small for T2K baseline) J. Boehm � Effect of CP on the phase term is δ→−δ hence the nomenclature δ CP � Oscillation measurement, and measurement of sin 2 2 θ 13 , depends on δ CP � If any angle is zero oscillation measurement is not sensitive to δ CP ⇒ measurement of θ 13 is critical for future CPV experiments R.J.Wilson/Colorado State University 12
T2K θ 13 sensitivity (normal hierarchy) MINOS – Nu2010 23 = 2.4 x 10 ‐ 3 eV 2 Δ m 2 sin 2 θ 12 = 0.8704 Δ m 2 12 = 7.6 x 10 ‐ 5 eV 2 sin 2 θ 23 = 1.0 Exposure: 750 kW X 5 X 10 7 s X 22.5 kt fid. mass � sin 2 θ 13 sensitivity depends on unknown δ CP ; usually given for δ CP =0 13
Systematics: ν μ → ν e � Expected backgrounds at Super ‐ K � Intrinsic ν e in beam, ~60% � False e ‐ candidates, e.g. from NC π 0 , ~40% ⇒ important to understand systematics on these backgrounds � Analysis goal is to keep fractional uncertainty on each background source to < 10% R.J.Wilson/Colorado State University 14
ν μ → ν e appearance sensitivity δ CP = 0, Δ m 223 = 2.5 x 10 ‐ 3 eV 2 Effect of systematics Design Goal: 3.75 MW × 10 7 s � Sensitivity goal : 0.006 (0.008) for normal (inverted) hierarchy (~1/20 CHOOZ limit) 15
ν μ disappearance ( ) ν → ν = ≈ θ Δ obs null 2 2 2 P ( ) N / N ( E ) sin 2 sin m L / 4 E μ ν ν ν ν x 23 32 Measured by Super-K obs N ν Δ m 32 2 sin 2 2 θ 23 sin 2 2 θ = 1.0 Δ m 2 = 2.7 x 10 –3 eV 2 ( ) x Φ ν x σ ν ND water R Far/Near Near detector Measured by flux near detectors Extrapolated from 16 MC verified by NA61
Systematics: ν μ → ν μ δ (sin 2 2 θ 23 ) � Estimated Systematics uncertainties � Normalization – 10% � Non ‐ QE/QE ratio – 20% � Energy scale – 4% δ ( Δ m 2 23 ) � Spectrum width – 10% R.J.Wilson/Colorado State University 17
Atmospheric parameters summary MI NOS & Supe r-K pre limina ry @ Nu10 � Narrow beam spectrum centered on oscillation maximum ⇒ good sensitivity to atmospheric parameters 90% c .l. T 2K � Expected sensitivity w/ 3.75 MW×10 7 s � Δ sin 2 2 θ 23 ≈ 0.01 MINOS � Δ m 2 23 < 1.0 x 10 ‐ 4 eV 2 R.J.Wilson/Colorado State University 18
T2K Beam & Near Detectors R.J.Wilson/Colorado State University 19
181 MeV Linac The JPARC Facility ND280 Neutrino Beamline (6 bunch Jan ‐ June 2010) 30 GeV Proton 3 GeV RCS ~ Synchrotron 20 Nakadaira ‐ san talk for more details R.J.Wilson/Colorado State University 20
Accumulated Protons Summer Shutdown 6 → 8 bunches Rep. 3.6 → 3.2 sec � First T2K run (January to June 2010) � ~50 kW stable operation; 3.23 ×10 19 protons for analysis � Second run started Nov. 16 – rapid ramp up to current 115 kW 21
Neutrino Monitor Near Detector at 280 m Off ‐ Axis Side Muon Range Detector ND280 Detector On ‐ Axis Monitor (INGRID) Barrel ECAL installation finished Oct 2010 Completes ND280! R.J.Wilson/Colorado State University 22
INGRID On ‐ axis monitor First e ve nt Beam Profile X Beam Profile Center X � Monitor beam direction, intensity and mean energy � Off ‐ axis angle measurement accuracy goal 1 mrad (< 15 MeV on off ‐ axis peak energy) � Beam position resolution ~ 7 cm ⇒ ~3 mm shift at proton target � ~ 10k ν interactions per day at full power � Six bunch beam structure R.J.Wilson/Colorado State University 23
ND280 off ‐ axis neutrino events Event Rates (P0D+FGD)/10 21 PoT : 600k μ ‐ only 300k μ ‐ p 40k μ ‐ π 0 8k e ‐ only 5k e ‐ p 0.8k e ‐ π 0 R.J.Wilson/Colorado State University 24
Off ‐ axis Detector Interaction Vertices P0D � Contained vertices reconstructed in P0D and FGD � Lines show (approximate) iso ‐ contours of off ‐ axis angle � Outer corner is roughly 20% further off ‐ axis than inner corner R.J.Wilson/Colorado State University 25
Far Detector : Super Kamiokande IV � More details in Roger Wendell’s Talk � 50 kt (22.5 kt fid.) Water Cherenkov detector: 11,129 20” PMTS in inner detector (ID) and 1885 8” PMTS in outer detector (OD) � T2K � Dead ‐ timeless read out electronics and DAQ upgrade in 2008 � GPS system used to select time arrival of beam events R.J.Wilson/Colorado State University 26
Unbiased event selection ν μ disappearance analysis E vis > 30 MeV n o of rings =1 μ ‐ like ring Timing coincident w/ beam time (+TOF) ν e appearance search Fully contained (No OD activity) E vis > 100 MeV Vertex in fiducial volume n o of rings =1 (vertex > 2 m from wall) e ‐ like ring No decay electron Inv. mass w/ forced ‐ found 2 nd ring < 105 MeV rec < 1250 MeV E ν � SK event selection decided before the run � Possible because SK is a mature & well understood detector 27
T2K Events in Super ‐ K p μ = 1438 MeV/c p μ = 1061 MeV/c 2 decay ‐ electrons 1 decay ‐ electron Jan ‐ June 2010 # of events 33 Fully ‐ Contained (FC) + fiducial volume cut 23 + visible E > 30 MeV (FCFV) 28
Super ‐ K Time Distribution Jan ‐ June Nov. ‐ Dec. � GPS works well ‐ very good time synchronization between T2K beam and Super ‐ K � Change 6 ‐ >8 bunches since Nov. evident ∆ T 0 = SK trig time -T2K beam trigger time 29
2010/2011 Run � Started Nov. 18 th � ~50% increase in data in 3 weeks � Current beam power ~115 kW � Aim for 150 kW × 10 7 s by July 2011 � 10x 1 st run data July 2011 goal � sensitivity to sin 2 2 θ 13 ≈ 0.05 Design Goal: 3.75 MW × 10 7 s R.J.Wilson/Colorado State University 30
Summary � 1 st run January–June 2010 � Continuous beam at ~50 kW, accumulated 3.23 x 10 19 PoT � Good overall stability of beam and detector performance � Measured 23 neutrino beam events (FCFV) at Super ‐ K � Expect first results by winter 2011 conferences � Summer/fall shutdown � New kicker magnet & power supplies installed � INGRID modules assembly and installation � Calorimeter modules installation completed ‐ full coverage at ND280 � 2 nd run November 2010 – Summer 2011 � Aim for 150 kW x 10 7 s by July 2011; currently > 110 kW � 90% c.l. sensitivity sin 2 2 θ 13 ~ 0.05 R.J.Wilson/Colorado State University 31
Supplementary R.J.Wilson/Colorado State University 32
T2K θ 13 sensitivity (inverted hierarchy) MINOS – Nu2010 � Similar to normal hierarchy � T2K insensitive to matter effects R.J.Wilson/Colorado State University 33
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