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

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

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

4. 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. 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

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

7. 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

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

9. T. Nakaya9 (5.8  significance) Puzzle

10. 0 1 2 3 4 5 6 7 8 10 1.3mm # photons HAMAMATSU MPPCBig TPC w/ MicroMegas T2K-ND280OA

11. 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 2010~2015 2015~ 2020~ TN personal view

12. 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. 13 295km water C v Hyper-K @ Kamioka CP sensitivity sin 2 2  13  Discovery potential of ＣＰ V phase  in 20° ～ 160° 、 200° ～ 340°

14. Okinoshima 658km 0.8deg. Off-axis 100 kt Lq. Ar δ =0 ° ν e Spectrum Beam ν e Background CP Measurement Potential NP08, arXiv:0804.2111 δ =90 ° δ =180 °δ =270 ° sin 2 2 θ 13 =0.03,Normal Hierarchy 33 14 @ 658km beam only sin 2 2  13 

15. expected event rate @ Mton Water Cherenkov detectorexpected event rate @ 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. Kaneyuki @ NP08

16.  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

17. 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

18.  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

19.  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. 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, 2004 @ T2K meeting Realization/Operation in 2010

21. 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. 26 signalbackground  =0  =  /2 total   e e   e 5361809133706645026   e 5368301782399657297430 Better with antineutrinos How correct they are?

27. 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) 72982751187095285548905556756 FC, in Fid. vol. Evis>100MeV 51698 (71%) 18245 (24%) 4783 (67%) 1307 (46%) 4007 (82%) 437 (79%) 6529 (97%) 1ring 27596 (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 0.35-0.85 28 (0.04 %) 1008 (1.3%) 0.9 (0.01 %) 70 (2%) 455 (9.3%) 20 (4%) 3991 (59%) cos  <0.9 22 (0.03 %) 713 (1.0%) 0.249 (2%) 394 (8%) 12 (2%) 3513 (52%) M  0 <100MeV 14 (0.02 %) 340 (0.5%) 0.225 (0.9%) 358 (7%) 10 (2%) 3279 (49%)

28. 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) 89052430535871972428644643895526 FC, in Fid. vol. Evis>100MeV 65825 (74%) 20041 (47%) 41435 (71%) 16659 (23%) 5498 (85%) 3333 (76%) 5302 (96%) 1ring 27443 (31%) 4878 (11%) 30652 (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 0.35-0.85 24 (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%)

29. signalbackgroud  =0  =  /2   e e  32792429354263589  32644065443610229391 (sin 2 2  13 =0.1) reconstructed E distribution    =0  =  /2 E rec  +  BG  +  e  e BG signal+BG

30. signalbackgroud  =0  =  /2   e e  10495793542637910  10501493443610241415 (sin 2 2  13 =0.03) reconstructed E distribution    =0  =  /2 E rec  +  BG  +  e  e BG signal+BG

31.  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%

32. 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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34. A.Bueno et al NP08 (@Mito) on Mar-6-2008 34  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 00 00 44 44 45 25 40 60

35. A.Bueno et al NP08 (@Mito) on Mar-6-2008 35  No oscillation case  e appearance signal at various  cp  e  e 5 years 82000750146035  cp (deg)  cp (deg)090180270 sin 2 2 13 =0.1 2867206226593464 sin 2 2 13 =0.05 1489111913421908 sin 2 2 13 =0.03 9425068291266

36. A.Bueno et alNP08 (@Mito) on Mar-6-200836  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.

37. A.Bueno et al NP08 (@Mito) on Mar-6-2008 37  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

38. A.Bueno et alNP08 (@Mito) on Mar-6-200838  “ 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

39. A.Bueno et alNP08 (@Mito) on Mar-6-200839 200MeV 100MeV perfect 0 deg90 deg 180 deg 270 deg Assuming constant Gaussian resolution independent on energy Looks resolution is crucial (100MeV at most) 0 5 05 05 05 40 20 40 60

40. A.Bueno et alNP08 (@Mito) on Mar-6-200840 200MeV 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 ”