Near detectors for long baseline neutrino experiments T. Nakaya (Kyoto) 1T. Nakaya

2 For the T2K collaboration The detector is working inside of the UA/NOMAD magnet. Thanks to CERN.

T. Nakaya3 Near detector Far Detector Decay region MiniBooN E DetectorSciBooNE MiniBooNE beamline 100 m 440 m MINOS

Functions of Near Detectors 1. Measure the neutrino flux times cross section for the normalization of the neutrino event rate at the far detector. 1. (Data/MC) #  events = 0.8 ~ 1.8 ??? (10~20% error for  and 10~20% error for hadron production) 2. Beam e event rate for e appearance search 3. Background estimation. 2. Monitor the neutrino beam itself for the long life of the neutrino experiment. 1. Running for ~5 years or longer. 3. Study the neutrino cross sections. 1. Low energy nuclear physics: not well understood nor not well modeled. 4. Play ground of the new technologies for experimentalists. 1. MPPC, TPC w/ Micromegas in T2K, etc.. Challenge new ideas, new designs, etc.. T. Nakaya 4

5 protons Measurement of the event rateMeasurement of the event rate   Hadron Production  (E)   Intense beam Far detector Near: Far: R(E ): Far/Near Flux ratio  beam MC, hadron production P(E ): Neutrino Oscillation Probability Near detector

T. Nakaya6  event rate (1KT)  beam direction (MRD)  energy in interactions(MRD)

7 NC  0 candidate +N  +N+  0 e CCQE candidate CCQE candidate ( +n  +p) 3track event CC-1  (  +p+  ) candidate 1.3x2.5 cm 2 segmentation size

T. Nakaya8 m  Vertex Activity (VA) w/ VA (> 2MeV) w/o VA (< 2MeV)

T. Nakaya9 (5.8  significance) Puzzle

mm # photons HAMAMATSU MPPCBig TPC w/ MicroMegas T2K-ND280OA

T. Nakaya11 e appearance YES NO Big CPV & suppress e app. YES NO Tiny  13 New Idea Anti- measurement Build a gigantic detector. and anti- two osci. peak T2K/JPARC 2010~ ~ 2020~ TN personal view

water C v 12 J-PARC Power Upgrade KEK Roadmap →1.66MW Gigantic detector Water Cherenkov Liquid Ar. TPC O (~100k)ton Liq. Ar GUT Proton Decay Study Symmetry Violation between and

13 295km water C v Kamioka CP sensitivity sin 2 2  13  Discovery potential of ＣＰ V phase  in 20° ～ 160° 、 200° ～ 340°

Okinoshima 658km 0.8deg. Off-axis 100 kt Lq. Ar δ =0 ° ν e Spectrum Beam ν e Background CP Measurement Potential NP08, arXiv: δ =90 ° δ =180 °δ =270 ° sin 2 2 θ 13 =0.03,Normal Hierarchy 33 658km beam only sin 2 2  13 

expected event Mton Water Cherenkov detectorexpected event Mton Water Cherenkov detector expected events w/o oscillation  beam expected events with oscillation  beam  CC  NC  CC  NC  CC  NC beam  e  CC  NC  CC  NC beam  e E (GeV) events/Mton/1MW/yr/50MeV  and e in  beam should be carefully considered. K. NP08

 beam E rec after all cuts reconstructed E distribution  beam : 1.66MW 2.2yr  beam : 1.66MW 7.8yr sin 2 2  13 =0.1 E rec e signal  NC e beam  NC e signal  NC

Why a near detector?Why a near detector?  Water Cherenkov  Better understanding of the anti- beam.  Improve the knowledge of neutrino interactions, especially for anti-.  Liq. Ar. TPC  Resolution of the neutrino energy reconstruction including the effect of the feed- down from the high energy part.  Detector Performance  Neutrino Interactions Study and demonstrate the above physics&effects in the near detectors. T. Nakaya17

 SciBooNE  beam ~ 1GeV  2D view × 2  Segmentation: 2.5×1.3 cm 2 (effectively 2.5 × 1.3 )  Note: T2K-FGD 1×1 cm 2 (effectively 1× 2 ) T. Nakaya18 SciBooNE (Internal) MeV/c cm ignore

 SciBooNE (~10 cm tracking capability)  beam ~ 1GeV  2D view × 2  Segmentation: 2.5×1.3 cm 2 (effectively 2.5 × 2.6 )  Note: T2K-FGD 1×1 cm 2 (effectively 1× 2 ) T. Nakaya19 #tracks Aim a few mm segmentation ~1cm tracking and patter recognition capability (3D view)

20 Magnet (and side MRD) Electron calorimeter Fine Grained detector w/ or w/o water target Scintillator Tracker (TPC or chambers) Iron shield for  -ID T. Nakaya August 25, T2K meeting Realization/Operation in 2010

21 Magnet (and side MRD) Electron calorimeter Fine Grained detector Lq. Ar TPC Gas TPC One vague idea of TN Idea (2010?) ➝ Realization/Operation 2016?~ Scintillating fiber camera (1~2mm fiber) FGD w/ water scintillator

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26 signalbackground  =0  =  /2 total   e e   e   e Better with antineutrinos How correct they are?

number of events on each step (  beam 1.66MW 2.2yr sin 2 2  13 =0.1)   e e signal e CC (sin 2 2  13 =0.1) CC NCCCNC in Fid. (vector) FC, in Fid. vol. Evis>100MeV (71%) (24%) 4783 (67%) 1307 (46%) 4007 (82%) 437 (79%) 6529 (97%) 1ring (38%) 4316 (5.7%) 3005 (42%) 354 (12%) 2171 (44%) 277 (50%) 5779 (86%) e-like 1053 (1.4%) 3254 (4.3%) 85 (1.2%) 245 (8.6%) 2112 (43%) 271 (49%) 5685 (84%) no  -e decay 373 (0.5%) 2912 (3.9%) 33 (0.5%) 220 (7.7%) 1807 (37%) 259 (47%) 5248 (78%) E rec (0.04 %) 1008 (1.3%) 0.9 (0.01 %) 70 (2%) 455 (9.3%) 20 (4%) 3991 (59%) cos  < (0.03 %) 713 (1.0%) (2%) 394 (8%) 12 (2%) 3513 (52%) M  0 <100MeV 14 (0.02 %) 340 (0.5%) (0.9%) 358 (7%) 10 (2%) 3279 (49%)

number of events on each step (  beam 1.66MW 7.8yr sin 2 2  13 =0.1)   e e signal e CC (sin 2 2  13 =0.1) CC NCCCNC in Fid. (vector) FC, in Fid. vol. Evis>100MeV (74%) (47%) (71%) (23%) 5498 (85%) 3333 (76%) 5302 (96%) 1ring (31%) 4878 (11%) (52%) 4249 (5.9%) 2589 (40%) 2293 (52%) 4783 (87%) e-like 1486 (1.7%) 3355 (7.8%) 562 (1%) 3319 (8.6%) 2514 (40%) 2247 (51%) 4717 (85%) no  -e decay 586 (0.7%) 2801 (6.5%) 209 (0.4%) 3163 (4.5%) 2076 (32%) 2169 (49%) 4701 (85%) E rec (0.03 %) 885 (2%) 17 (0.02 %) 1154 (2%) 268 (4%) 449 (10%) 3568 (65%) M  0 <100MeV 9 (0.01 %) 433 (1%) 12 (0.02 %) 598 (0.8%) 229 (4%) 391 (9%) 3265 (59%)

signalbackgroud  =0  =  /2   e e   (sin 2 2  13 =0.1) reconstructed E distribution    =0  =  /2 E rec  +  BG  +  e  e BG signal+BG

signalbackgroud  =0  =  /2   e e   (sin 2 2  13 =0.03) reconstructed E distribution    =0  =  /2 E rec  +  BG  +  e  e BG signal+BG

 beam uncertainty for e ( e ) signal QE+nonQE nonQE reconstructed E distribution Uncertainty  flux  (  ) →  ( e )  (  ) →  ( e ) non-QE/QE Far/near efficiency energy scale ND FD cancelation between  and  beam is expected NA61 K2K  (N int 1kt )=4.1%  (nonQE/QE)=~6%  (NC/CC)=5%  (F/N)=3%  (E scale)=~2%  (eff)=~5%

background from  and   beam   CC QE 10%7%3% CC 1  0 6%1% CC 1   2%1%2% CC  →  N 0.8%0.3%0% CC n  0.6%0%0.5% NC elastic 0.2%0.3%2% NC 1  0 61%76%68% NC 1   4% 6% NC  →  N 6%5% NC n  10%6%13% mis PID 00 00 →N→N →N→N or  0

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A.Bueno et al NP08 on Mar  Shaded is beam e background, while histogram shows the osc ’ d signal.   cp effects are seen in 1 st and 2 nd osc. Maxima. (perfect resolution case) 0 deg90 deg 180 deg 270 deg

A.Bueno et al NP08 on Mar  No oscillation case  e appearance signal at various  cp  e  e 5 years  cp (deg)  cp (deg) sin 2 2 13 = sin 2 2 13 = sin 2 2 13 =

A.Bueno et alNP08 on Mar  The spectrum is fit by varying free parameters. (  CP and  13 )  Fit is based on Poisson probability of bin by bin. (binned likelihood)  right plot  True  CP =0, sin 2  13 =0.03  Best fit  CP =-0.5, sin 2  13 =0.031 Example of Fit (1 Pseudo-data) Neutrino Energy (GeV) Number of events Best fit data (50MeV bin) Perfect resol.

A.Bueno et al NP08 on Mar  This is perfect energy spectrum case  Cases at  cp =0,90,180,270 and sin 2 2  13 =0.1,0.05,0. 03 are overlaid.  Each point has 67,95,99.7% C.L contours Perfect resolution case

A.Bueno et alNP08 on Mar  “ Resolution ” includes;  neutrino interaction  Fermi motion  Nuclear interaction for final state particles.  Vertex nuclear activities (e.g. nuclear break up signal)  NC  0 event shape including vertex activity  detector medium  Ionization  Scintillation  Charge/light correlation  Signal quenching (amount of ionization charge/scinti. light is non-linear to dE/dx. E.g.including recombination )  hadron transport  Signal diffusion and attenuation  readout system including electronics  Signal and Noise Ratio  Signal amplification  Signal shaping  reconstruction  Pattern recognition   0 event shape  Particle ID We assume these effects causes Gaussian resolution, then see the results

A.Bueno et alNP08 on Mar MeV 100MeV perfect 0 deg90 deg 180 deg 270 deg Assuming constant Gaussian resolution independent on energy Looks resolution is crucial (100MeV at most)

A.Bueno et alNP08 on Mar MeV 100MeV perfect 200MeV resolution can still make some results, however, 100MeV is really preferable to see the 2 nd oscillation maximum visually. “” robustness of the result ”