April 26, McGrew 1 Goals of the Near Detector Complex at T2K Clark McGrew Stony Brook University Road Map The Requirements The Technique Muon Neutrino Disappearance Electron Neutrino Appearance Our solutions ISS Meeting – RAL

April 26, McGrew 2 T2K is Easy You only need to build A neutrino beam A far detector And compare The near neutrino fluxes The far neutrino fluxes It is just a counting experiment Or at most, a spectral measurement By the same measure, all physics is easy

April 26, McGrew 3 Super-Kamiokande III 40 m Restored to original configuration Start taking data in June 2006 Preliminary runs from 8:07 pm April 23rd 40% PMT Coverage New Acrylic PMT covers 5% light loss (i.e. “38%” PMT coverage) Solar Neutrino Trigger to 4.5 MeV Reduced “Radon” Contamination VERY A VERY well understood detector

April 26, McGrew 4 Measuring ν μ Disappearance w/ SK Measure E ν with 1-ring mu-like events in SK QE events (black) Backgrounds CC single pion (red) NC single pion (yellow) CC+NC multi pion (other)

April 26, McGrew 5 Measuring ν e Appearance w/ SK Measure with 1-ring electron-like events Backgrounds intrinsic ν e (60%) NC single π° (40%) other (negligible)

April 26, McGrew 6 Ratio of Far to Near Fluxes SK/ND280 varies by “large factors” SK/ND2k remains almost constant. However, cannot use ratio of event rates because oscillations distorts the shape of the neutrino spectra. Must use neutrino flux vs neutrino energy. CCQE Other

April 26, McGrew 7 Predicting Event Rates at SK Measure ν-flux at ND280 off-axis Quasielastic events (assume shape of QE cross-section!) Measure charge current cross-sections at ND280 CC quasi-elastic, CC single π +, &c (relative to QE) Understand pion kinematics in decay tunnel HARP, ND280 on-axis, CCQE at ND280 off-axis, &c Use to extrapolate flux to SK Use ND280 cross sections to predict events at SK Only need systematic comparable to statistics -- “Easy” with K2K, “Harder” with T2K

April 26, McGrew 8 Predicting the SK π° Background Measure ν μ N -> π°ν μ N vs. π° momentum Determine P π° /P ν vs P ν Measure ν μ N -> π + μ - N Measure ν μ n -> π°μ - p Measure φ 280 (E ν ) Determine φ SK /φ 280 (E ν ) We want to estimate without depending on MC cross-section information We can measure Assume At “fixed P ν ” Case Study

April 26, McGrew 9 Determining P π° / P ν vs P ν -Q 2 Hadronic part of interaction is the “same” so expect fraction of Q passing to π° to be the “same” Hadronic part different, but can be “related” by an isospin rotation Still need dσ/dE ν dQ 2 no Pauli blocking

April 26, McGrew 10 Internal Cross Checks ν μ N -> π + μ - N ν μ N -> π°ν μ N φ 280 (E ν ) φ SK /φ 280 (E ν ) ν μ n -> π°μ - p φ SK (E ν ) ν μ N -> μ - N Measurement vs “Cross Section” MC Measurement vs “Beam” MC to get 14% need ~8%

April 26, McGrew 11 Goals of the T2K Near Detectors Measure the ν μ and ν e flux going to Super-Kamiokande Determine ν μ spectrum and normalization using quasielastic interactions. Determine intrinsic ν e content of beam Predict the far/near ratio. Determine the ν-Oxygen cross sections Use to predict event rates at SK CC: Understand SK single ring muons NC: Understand SK single ring elec.

April 26, McGrew 12 Required Off-Axis Measurements ν μ n -> μ - p Determines neutrino flux Normalizes other cross sections ν e n -> e - p ν N -> μ - π + N : CC single pion cross section ν N -> μ - π – N: Nuclear rescattering ν n -> μ - π° p: CC single pion cross section ν N -> ν π° N: NC single pion cross section Multi pion production

April 26, McGrew 13 ND280 Detector Complex On-Axis Detector Determine Beam Profile Monitor Beam Direction Constrain π momentum distribution Off-Axis Detector Determine off-axis flux and shape Measure CC and NC Main tool to determine expectation at SK

April 26, McGrew 14 ND280 Off-Axis Detectors Positioned towards SK Measure off-axis flux Fine-grained to measure cross sections In the UA1 Magnet 0.2T transverse field

April 26, McGrew 15 Off-Axis PØD (π° detector) Forward part of Off- Axis NC interactions CC π° production ν e flux

April 26, McGrew 16 PØD Redux Active Scintillator Neutrino Target Two modules (scintillator and water + scintillator) NC π° reconstruction efficiency ~30% Expected to be higher for CC NC π° signal to noise ~2.3 E&M resolution ~15%/sqrt(GeV) Primary Goals Measure NC and CC π° production Systematics ~ 10% 440 MeV/c π˚ Activity in ECAL

April 26, McGrew 17 Anatomy of the PØD Upstream ECAL (USECAL) Central ECAL (CECAL) “Water” Target “Carbon” Target Length of ECAL is fixed (~35 cm) Preradiator: ~1 χ Radiator: ~4 χ Carbon Length ≈ ½ Water Length ~50% H 2 O by mass Fiducial Volume is ~30% H 2 O Required for “Bkgd. Sub.”

April 26, McGrew 18 P0Dule/ECal modules Use same module design for all P0D elements Differences Between P0Dules and Ecal Modules P0Dules Pb is 0.6 mm thick One Pb per two scintillator 60 P0Dules ECAL (Preshower) Pb is 2.0 mm (0.6mm) thick One Pb per scintillator 32 layers (16 PbODules) SciBars Absorber End-Caps Water Target (where required) Photosensor

April 26, McGrew 19 Off-Axis Tracker Downstream portion of PØD Determine charged particle momentum ν μ flux with QE CC single π production ν e flux with QE

April 26, McGrew 20 Tracker Redux Active Scintillator Neutrino Target Two modules (scintillator & scintillator + water) Measure activity near the neutrino vertex TPC to measure momentum and provide PID σ P /P < 10% for P < 1 GeV 3 σ e/μ separation between 300 MeV/c and 1 GeV/c Measure particle charge (μ - /π + separation) Simulated TPC track with 8mm x 8mm pads

April 26, McGrew 21 Side Muon Range Detector (SMRD) Embedded in UA1 Magnet Measure momentum of side-going muons

April 26, McGrew 22 Finally T2K Systematic Error Goals 10% on electron neutrino appearance (background) 5% on far/near events vs energy for muon neutrinos. Life is not simple We need flux, cross-section and efficiency independently BUT, measure the product Depend on external inputs to break the loop The End

April 26, McGrew 23 The End

April 26, McGrew 24 PØD Physics Goals Measure SK ν e appearance backgrounds NC π˚ (40% of background w/ large a priori uncertainty) Exclusive single π˚ production Angular and Momentum Distributions Inclusive NC and CC production Beam ν e Interactions (57% of background) Measure quasi-elastic electron neutrino production Complementary to charge particle tracker Word about Systematics: Our SK background subtraction goal is 10%. That implies the total SK systematic for ν e, and π° must each be ~14%.

April 26, McGrew 25 PØD π˚ Momentum Distribution Shape of SK/P0D π˚ momentum ratio expected to be nearly flat Background Region Don't depend on flatness in analysis, but gives hope that the systematics can be controlled! Need sensitivity to π° between 200 MeV/c < P < 800 MeV/c

April 26, McGrew 26 Anatomy of the PØD Upstream ECAL (USECAL) Central ECAL (CECAL) “Water” Target “Carbon” Target Length of ECAL is fixed (~35 cm) Preradiator: ~1 χ Radiator: ~4 χ Carbon Length ≈ ½ Water Length ~50% H 2 O by mass Fiducial Volume is ~30% H 2 O Required for “Bkgd. Sub.”

April 26, McGrew 27 P0D NC π˚ Reconstruction Basic Requirements No “upstream” activity P0D Hits in 20 ns window No μ/π track (proton OK) “Separated” Shower in P0D Projected vertex in Fid. Eff. ~ 30% above 300 MeV/c BKGD from CC events ~ 20 % 440 MeV/c π˚ Activity in ECAL 12cm – 50cm