T2K Oscillation Strategies Kevin McFarland (University of Rochester) on behalf of the T2K Collaboration Neutrino Factories 2010 October 24 th 2010

24 October 2010K. McFarland, T2K Oscillation Strategy2 The T2K Experiment

24 October 2010K. McFarland, T2K Oscillation Strategy3 The T2K (Tokai to Kamioka) Experiment 2.5˚  beam  beam TokaiKamioka Tokai Kamioka 295 km Super-K The Super-Kamiokande detector JPARC Japan Proton Accelerator Research Complex

24 October 2010K. McFarland, T2K Oscillation Strategy4 Characteristics of T2K ● High intensity beam ● Off-axis detectors: ● The detectors are at 2.5 ° off-axis from the beam, which tunes the energy and shape. ● A massive, well understood, far detector SK. ● A complex suite of near detectors: ● INGRID is on-axis for beam direction monitoring. ● ND280 has multiple sub-detectors and regions, focused on specific backgrounds at SK.

24 October 2010K. McFarland, T2K Oscillation Strategy5 JPARC Beam Facility Jul. 16, 2009 LINAC RCS Main Ring 30 GeV TS ND280 Super-K Muon monitor Beam dump

24 October 2010K. McFarland, T2K Oscillation Strategy6 JPARC Beam ● Protons collide with a graphite target, producing charged pions. ● Design 30 GeV, 750 kW ● The positive pions are focused by horns, and enter the decay volume. ● The decay produces  and  + ● The length is tuned, to minimize the number of  + that decay, producing anti- . Target & horns p Super-K 2.5˚ ND m~280 m Beam dump  monitor INGRID Decay Volume Side view ( beamline) Top view ( beamline) INGRID ND280 Beam dump  monitor Target & horns Main Ring

24 October 2010K. McFarland, T2K Oscillation Strategy7 Off-axis Design ● The detectors are placed off-axis from the beam. ● 1 st oscillation E ~ 0.6 GeV. ● Beam peak ~ 0.7 GeV, CCQE interaction dominates, allows E reconstruction. ● The angle can be varied from 2.5 ° to 2.0 ° off-axis.   

24 October 2010K. McFarland, T2K Oscillation Strategy8 Goals of T2K

24 October 2010K. McFarland, T2K Oscillation Strategy9 Oscillation Goals ● T2K will make two oscillation measurements ●  disappearance: ● Observe a deficit of  in the beam at Super-K. ● Improved measurements on  23 and  m ● e appearance: ● Search for increased e in the beam at Super-K ● If found, would establish non-zero  13 ● With other measurements, may probe mass hierarchy and δ

24 October 2010K. McFarland, T2K Oscillation Strategy10 Conceptual Measurement of   →  e ● # of observed SK N e SK = P(   e )   SK (  )   ( int. water ) ●  SK (  )   (  int.)= R( SK/ND )   ND (  )   (  int. water ) = R( SK/ND )  N  ND ● R( SK/ND ) : Far to Near flux ratio ● Estimated from simulation, using measurements from beam monitors and CERN NA61. Near Detector Measurement 0 m~280 m295 km Target ND280Super-K N e SK N  ND R(SK/ND)

24 October 2010K. McFarland, T2K Oscillation Strategy11 Conceptual Measurement of   →  x ● Disappearance measurement gives  23,  m 2 32 N null = R x  ND x  water R(Far/Near) Extrapolated from MC, verified by NA61  water Measured by near detectors  ND Measured by near detectors (8.3 x GeV) N obs Measured by Super-K P(   x ) sin 2 2  = 1.0  m 2 = 2.7 x 10 –3 eV 2 sin 2 2  m2m2m2m2

24 October 2010K. McFarland, T2K Oscillation Strategy12 Eventual e Appearance Sensitivity sin 2  23 = 1.0 is assumed 8x10 21 POT ~ kW sin 2  13 = 0.1 # of events in 0.35 ~ 0.85 GeV Signal… 143 Beam e BG… 16 BG from  … 10  m 2 13 =2.4  10-3 eV 2,  =0 (OA2.5° )

24 October 2010K. McFarland, T2K Oscillation Strategy13 e Appearance Sensitivity: Effect of  sin 2  23 = 1.0 is assumed 8x10 21 POT ~ kW

24 October 2010K. McFarland, T2K Oscillation Strategy14 Detectors

24 October 2010K. McFarland, T2K Oscillation Strategy15 Super-Kamiokande ● 50 kt water Cherenkov (fid. volume: 22.5 kt) ● 11k 20-inch PMTs (inner detector) ● Been running stably with full coverage and new electronics since summer ● T2K beam is triggered in real time, minimizing atmospheric and cosmic ray backgrounds.

24 October 2010K. McFarland, T2K Oscillation Strategy16 Signals and Backgrounds ● There are 3 main backgrounds at Super-K: ●  mis-PID: – ~1% for CCQE ● Beam e contamination: – ~0.4 % at  spectrum peak – Measured by near detector ● Mis-reconstructed NC  0 events: – Minimized by small number of high E s in off-axis beam – Cross-section measured by near detector  Sharp edge e 'Fuzzy' ring 00

24 October 2010K. McFarland, T2K Oscillation Strategy17 T2K's 1 st SK Event 2 nd ring 3 rd ring [ 1 st ring + 2 nd ring ] Invariant mass: MeV/c 2 (close to  0 mass) Momentum: MeV/c 1 st ring 06:00 JST, Feb. 24, 2010

24 October 2010K. McFarland, T2K Oscillation Strategy18 SK Event Selection ● Beam events selected using GPS time. ● Cuts were decided and fixed before looking at data ● Will likely be tightened with higher statistics

24 October 2010K. McFarland, T2K Oscillation Strategy19 INGRID: On-axis Near Detector ● Monitors the Neutrino beam flux and direction. ● Counts CCQE neutrino events, using 14 modules arranged in a cross (7H & 7V). ● 11 scintillator planes, 9 iron layers, per module. ● ~1 day of running is sufficient statistics to monitor the beam. beam modules

24 October 2010K. McFarland, T2K Oscillation Strategy20 INGRID Data ● Select fully contained events. ● Count in 7 modules gives the beam profile. ● Stable over year run. 1 mrad

24 October 2010K. McFarland, T2K Oscillation Strategy21 ND280: Off-axis Near Detector ● 2.5 ° off-axis, to match SK. ● Inside the UA1 magnet (0.2T), for charge discrimination & momentum measurement. ● Two main regions: ● P0D upstream ● Tracker downstream Beam beam Magnet (open) Exploded detector view

24 October 2010K. McFarland, T2K Oscillation Strategy22 First ND280 Event

24 October 2010K. McFarland, T2K Oscillation Strategy23 Statistical and Systematic Uncertainties

24 October 2010K. McFarland, T2K Oscillation Strategy24 Most Important Anticipated Systematics ● Appearance   →  e ● Intrinsic e in beam ● Fake e - in far detector (e.g., NC  0 ) ● If oscillation probability is large, will eventually limited by signal eff. (fiducial volume, energy reconstruction of e events) ● Disappearance   →   ● Beam energy, normalization ● Detector fiducial volumes and energy scales ● Non-QE background in Super-K

24 October 2010K. McFarland, T2K Oscillation Strategy25 T2K Analysis Strategy ● We plan to bring overwhelming force on multiple fronts to beat down systematics, perhaps out of proportion to their actual impact ● Our tools of choice ● Experimental design: primarily off-axis beam, partial cancellations from near-to-far comparisons ● “Redundant” methods: build complete data-based models for beam, neutrino interactions, detectors to cross-compare and study systematics Systematic uncertainties place flowers in rifles of T2K Collaborators outside the US Pentagon (1967), (photo: Bernie Boston)

24 October 2010K. McFarland, T2K Oscillation Strategy26 Super-K prediction ND280 flux Transfer function Cross sections Super-K response NA61 data Geometry INGRID data Super-K atmospheric analysis ND280 data Beam Simulation Interaction models ND280 data External data ND280 response Super- Kamiokande beam data Oscillation measurements Detector simulation Super-K flux

24 October 2010K. McFarland, T2K Oscillation Strategy27 Example: Flux Tuning ● Beam simulation gives a prediction for flux ● Protons monitors provide initial proton direction ● Hadron production tuned for consistency with NA61 (T2K target replica) data ● Muon monitor crosscheck ● INGRID (on axis) detector determines beam direction ● Rate also constrains flux ● Off-axis near detector flux can be used with near/far ratio or “matrix method” ● May also be used to tune beam simulation

24 October 2010K. McFarland, T2K Oscillation Strategy28 Summary

24 October 2010K. McFarland, T2K Oscillation Strategy29 Prospects for 2011 ● Next run starts Nov 2010 ● Expect beam of 150 kW × 10 7 s by July 2011 ● Sensitivity to sin 2 2  13 ~ 0.05 ● The early results are still statistics limited ● We'll have time to explore these techniques and see which are the most effective July 2011 Target July MW × 10 7 s