SciBooNE experiment （実験の意義・目的と現状など） Y.Hayato

1. Neutrino – nucleus scattering experiment ニュートリノ振動実験 ニュートリノと電子や核子散乱により生成した 　　　　　　　荷電粒子(など)を観測することで行う。 シミュレーションプログラムを用いて期待される分布を求め、 データと比較することで振動パラメータを決定する。 できるだけ「正しい」シミュレーションプログラムが必要 反応標的として酸素や炭素などを用いる場合、 原子核であることの影響が大きい。 正確なモデル化を行うことも非常に難しい。 反応の詳細を実験データから知ることが必要 １）散乱断面積 a)反応の全散乱断面積 b)微分散乱断面積 ２）生成粒子とそれらの運動量分布

2. Neutrino interactions above 100MeV Charged current quasi-elastic scattering m+ n →m- + p Neutral current elastic scattering m+ N →n + N Single p,h,K resonance productions nm+ N →l + N’ + p (h,K) Coherent pion productions nm+ X →l + X’ + p Deep inelastic scattering nm+ N →l + N’ + mp(h,K) n cross-sections (l : lepton, N,N’ : nucleon, m : integer) n cross-sections Total (NC+CC) CC Total CC Total s/E (10-38cm2/GeV) CC quasi-elastic DIS DIS (CC) CC single p NC single p0 En (GeV)

3. Existing n – nucleus scattering data Mainly from the bubble chamber experiments Bubble chamber is a very powerful detector. High efficiency in detecting even for low momentum charged particles. Limited by statistics. ( Scanned by eye, basically. ) 　　　A few tens to hundreds events. A few thousands events at most. m / charged p separation was rather difficult. p0 detection efficiency was not high. (ANL) (ANL) Also, the flux estimation has large uncertainties. Still, there seems to exist quite large uncertainties even in the current running experiments. Determination of the “absolute” cross-section is difficult.

3. Existing n – nucleus scattering data Recent experiments 1) K2K Water Cherenkov detector SciFi detector SciBar detector 2) MiniBooNE Mineral oil detector ( Mainly Cherenkov ) Ring imaging Cherenkov detector Large fiducial volume High efficiency for low momentum p0 Threshold for protons are so high. ( ~ GeV/c ) SciFi Water target tracking detector. Passive ( non-active ) volume is fairly large pions/protons stop in the passive region. High statistics & precise measurement is very important.

4.Existing neutrino beam line FNAL 8GeV Booster neutrino beam line Intense low energy neutrino beam Mean energy of neutrino flux 0.7GeV ( peak at 0.6GeV ) Neutrino beam flux @ SciBooNE hall (Neutrino flux) x (cross-section) nm: 92.9 % nm: 6.5 % ne: 0.6 % ne: 0.05% Mean En 1.1 GeV Peak En 0.8 GeV

4. Existing neutrino beam line FNAL 8GeV Booster neutrino beam line Possible to deliver both neutrino and anti-neutrino beams. There are only a few low energy anti-neutrino data available. Mean En ~ 0.6 GeV ( Peak En ~ 0.45 GeV ) Anti neutrino beam flux @ SciBooNE hall (Anti neutrino flux) x (cross-section) nm ~83% nm ~16% ne ~0.2% ne ~0.4% Average energy : 1.0GeV (nm + nm) 0.9GeV (nm only) nm ~63% nm ~36% ne ~0.4% ne ~0.6% Averaged r<2m 0.5 1 1.5 2 1 2 3 (GeV) (GeV)

4. Existing neutrino beam line FNAL 8GeV Booster neutrino beam line Energy spectrum is quite similar to the T2K neutrino beam. Precise study of neutrino interactions with this beam is expected to provide important information for the T2K experiment. Full active scintillator detector similar to SciBar will be used as a near detector of the T2K experiment. T2K FNAL 8GeV Booster delivers ~ 2 x 1020 protons to the target in a year of running. Flux (normalized by area) SciBooNE K2K 0.5 1 1.5 2 En (GeV)

Fermilab Visual Media Services 5. SciBooNE Experiment Bring the K2K-SciBar detector to the FNAL Booster neutrino beamline Booster Fermilab Visual Media Services SciBooNE Detector Target & Horn

5. Detectors of the SciBooNE experiment Muon Range Detector (MRD) 1) SciBar detector Neutrino interaction target Tracking detector 2) Electron catcher Spaghetti calorimeter Lead as converter 3) Muon range detector Sampling calorimeter Measure muon momentum SciBar n beam Electron Catcher (EC)

n 5. The SciBar detector Extruded scintillator 3m reconstruct vertex Full Active tracking detector Extruded scintillator with WLS fiber readout Cell size : 2.5 x 1.3 x 300cm3 Light yield :7~20p.e. /MIP/cm (2 MeV) reconstruct vertex identify the interaction Extruded scintillator (15t) 3m n Multi-anode PMT (64 ch.) 3m High efficiency even for the short tracks Can identify low momentum protons above ~ 450 MeV/c. 1.7m Wave-length shifting fiber PID (p/p) & momentum measurement by dE/dx.

5. The Electron Catcher “spaghetti” calorimeter used in CHORUS Fibers 1mm diameter fibers in the grooves of lead foils Readout Cell PMTs Each 4 x 4cm2 cell is read out from both ends 8 cm 4 cm 2 planes (11X0) Horizontal: 32 modules Vertical : 32 modules 262 cm n Beam Total 256 readout channels Expected energy resolution 14%/√E

5. Muon Range Detector (MRD) MRD built with used scintillators, iron plates and PMTs to measure the muon momentum up to 1.2 GeV/c. Iron Plates 305 x 274 x 5 cm3 Total 12 layers Scintillator Planes Alternating horizontal and vertical planes. Total 362 channels.

6. Expected interaction rates ( neutrino mode ) Beam time June 2007 ~ Summer 2008. Protons on target 1 x 1020 for neutrino 1 x 1020 for anti neutrino # of nm events [/10tons/1E20POT] Fraction CC-QE 41,100 41.0% CC-1pi 23,500 23.5% CC-coherent 1,500 1.5% CC-other 5,500 5.5% NC-1pi 8,500 8.5% NC-coherent 900 0.9% NC-other 1,700 1.7% NC-elastic 17,400 17.4% Dominant DIS etc. Small fraction

Neutrino interaction studies at SciBooNE 1. n quasi-elastic scattering (n + n -> m-+p) Dominant interaction mode 41K events (41%) 2 tracks 1 MIP and 1 large dE/dx tracks p Basically 2 body interaction m Incoming n direction is fixed. Real n event in K2K Expected direction of proton is calculated from observed m. Real SciBooNE Data

Neutrino interaction studies at SciBooNE 2. n quasi-elastic scattering ( n + p -> m+ + n ) Free proton scattering check of nuclear model Detected as a 1-track event in SciBar Excellent n energy and q2 resolution Expect ~9,000 CCQE events after cuts, 80% purity No data anti-nm CC-QE candidate (nm + p  m + n) Real SciBooNE Data

Neutrino interaction studies at SciBooNE 3. Single p production ( n + n -> m- + p + p+ etc ) Dominant background for nm disappearance At BNB energies Second dominant : CC1p+ T2K needs to reduce uncertainty of non-QE/QE ratio Currently ~20% Try to reduce less than 10%. p m nm disappearance measurement error (90%CL) d(sin2 2q) d(Dm2) stat. only d(nQE/QE)= 5% d(nQE/QE)=20%

Statistics : Sufficient for ~ 5% measurement Neutrino interaction studies at SciBooNE 3. CC Single p production ( n + n -> m- + p + p+ etc ) Expect ~2,800 CC-1p+ events after cuts m p m p p m 3 tracks 2 MIPs 1 large dE/dx 2 tracks 2 MIPs 2 tracks 1 MIP 1 large dE/dx Vertex activity cuts separate n+pm-pp+ from n+nm+np+ Statistics : Sufficient for ~ 5% measurement

Neutrino interaction studies at SciBooNE 4. NC Single p production ( n + n -> m- + p + p+ etc ) Dominant background to ne appearance For the 1st phase of T2K, need to reduce systematic error down to ~10%. s(n+pn+p+p0) T2K ne appearance sensitivity plot - stat. only - dBG=10% - dBG=20% sin2 2q13 sensitivity 10-2 Projected SciBar at K2K Projected SciBar at BooNE 1 2 3 4 5 Exposure /(22.5kt x yr)

Timeline of the SciBooNE experiment 2005 Summer Collaboration formed 2005 Dec. Proposal 2006 Jul. Detectors move to FNAL 2006 Sep. Groundbreaking 2006 Nov. EC assembly 2007 Feb. SciBar assembly 2007 Mar. MRD assembly 2007 Mar. Cosmic ray data taking 2007 Apr. Detector installation 2007 May. Commissioning 2007 Jun. Anti-neutrino beam run start 2008 Oct. Neutrino beam run start 2009 Apr.(?) Anti-neutrino beam run start 2009 July.(?) End of the data taking start In total ~ 1 year of data taking

Accumulated POT ( June 2007 ~ Dec. 2007 ) n mode ( June ~ Aug. 2007 ) n mode ( Oct. 2007 ~ ) Delivered POT: 5.45x1019 Detector live time fraction ~95% Analyzed POT : 4.3x1019

SciBar event selection criteria for the event rate and the other basic studies SciBar detector More than 3 hits in each view Threshold: 2 p.e Track length > 4 layers Vertex in fiducial volume -130cm<x<130cm -130cm<y<130cm 2.62cm<z<157.2cm (2nd~60th layer) Require hit in the most downstream layer Within 2msec on-timing window Longest track vertex Fiducial volume

MRD event selection criteria for the event rate and the other basic studies Scintillator Iron plate n beam veto Require at least 4 planes Fiducial Volume(9 iron planes) muon Reconstruction Hits on 4 scintillator planes are required ( 2vertical, 2horizontal) Fiducial Volume -132cm < X < 132cm -110cm < Y < 110cm 9 iron planes (thickness of 1plane ~2inch) FV mass ~ 21.1ton Timing Cluster within 2msec time window is selected

Event displays TOP view SIDE view Real SciBooNE Data 3-track event

Event rate ( Summer 2007 anti-neutrino run ) Period: Jun. 12 - Jul. 28 +/-10% CC candidate events in SciBar ~ 5000 events (FV ~10.6 tons) CC candidate events in SciBar VERY PRELIMINARY 6/19 6/16 6/23 6/30 7/ 7 7/14 7/21 7/28 +/-10% CC candidate events in MRD ~10000 events (FV~19 tons) CC candidate events in MRD VERY PRELIMINARY 6/19 6/16 6/23 6/30 7/ 7 7/14 7/21

PRELIMINARY PRELIMINARY Event rate ( Autumn 2007 neutrino run ) CC candidate events in SciBar ~ 20000 events (FV~10 tons) CC candidate events in MRD ~ 50000 events (FV~21 tons) CC candidate events in SciBar CC candidate events in MRD c2 / ndf = 7.591 / 7 c2 / ndf = 15.4 / 7 PRELIMINARY PRELIMINARY Oct.20 Nov.03 Nov.17 Dec.01 Oct.27 Nov.10 Nov.24 Dec.8 Oct.20 Nov.03 Nov.17 Dec.01 Oct.27 Nov.10 Nov.24 Dec.8

Summary SciBooNE experiment will provide high statistics and high precision neutrino interaction data. Neutrino interaction measurement CC 1 p+ production NC p0 production ~ 10% precision Data taking was started in June 2007. Summer 2007 Anti neutrino run ~ 5 x 1019 POT Autumn 2007 Neutrino run ~ 5 x 1019 POT Data taking will complete in Summer 2008.