ニュートリノ振動実験で測定されたニートリノ－原子核反応断面積 と

1、日本物理学会2007年春3月27日首都大学東京n nm mnpgran sassom mm mm mm mm mn n cospemmemenn 22n nm m + n m m + pm m-p(em m, pm m) m mqeinelasticcc quasi elastic (qe)cc inelasticn nm m + n m m + p + p pn nm m-p(em m, pm m) m mp psn終状態測定可能。n入射分。n終状態n準弾性散乱（50%）n非弾性散乱（50%） 各種反応理解重要。lead glass ork2k n beamm mpcc-qe candida

2、te event 422222222228nncfnqeccmusqcmusqbqaegmdqd)()()(cosn np p 2222127201)(.)(aamqqf ()a,b,cq2、f1v、 f2v、 fa関数。l絶対高精度見積困難（不可能？）ld/dq2分布形ma測定。axial-vector form factor with a dipole approximation.(only given from n scattering)not used in fit (nuclear effect) 222m mm mm mm m mpeeqqeqe cosm mm mm mm mm

3、m cospemmemennqe 22withqqe2 (gev/c) 2qqe2 (gev/c) 2one-track events.two-track qe events.(a proton with qe kinematics)prd74(2006), 052002nm nm p)neutrino energy (gev) ( 10-38cm2)k2kcc-qe cross sectionma (gev/c2)k2k result0 0.8 1 1.2 10-1 1 10 mgggg (mev/c2)not nc-1p p0nc-1p p0.)(.)(.sysstatallccnc007

4、00010064001 p p model prediction with neut: 0.065model prediction with neut: 0.065neutplb 619(2005), 255-262nmpn *nnnmpp*t 08cm) 陽子de/dx識別 high track finding efficiency (99%) clear identification of interaction processcc-qe event candidatesignal region (s/n 1).).%(.lcallcccoherentcc901060802 p p mod

5、el prediction with neut: 2.667model prediction with neut: 2.667 1010-2-2new and modified models are proposed to explain the small cross section.0.65x10-40prl95, 252301 (2006)coherent p p cross section15n*16on nn np16on nk+15n*2,200nsmcl first observation of g rays from de-excitation of nuclei induce

6、d by neutrino interactions. l good confirmation of prompt g-ray tag in the proton decay search.l good nc samples for neutrino oscillation study.l 60% nc-elasticl 80% nc interactions.nucl.phys.proc.suppl.159 (2006), 44-49 2.5deg beam center28.5mground leveloff-axis detectoron-axis detectorneutrino pr

7、ofile & the beam centermagnet: 0.2 t outer: 6.1m(h) x 5.6m(w) x 7.6m(l) inner: 3.6m x 3.5m x 7.0mneutrino beam flux & spectrumneutrino interactionssk n near detectorbeam dumpm-monitordecay volumetarget &hornextraction point280moaoa3 oa0 oa2 oa2.5 n energy spectrum (flux cross section)osc

8、illation prob. l=295kmdm2=2.5 10-3, 3.010-3ev20.1 events/ton/spillreuse of ua1 magnetmuon range detectorp0ddedicated p p0detectorecal forp p0n ne2fgd + 3tpc for n nm mw/ water targetw/ micromegas8mmua1/nomad magnet w/ 0.2t(3.5 3.6 7m3)fgd scintillator10mm1mm1mmhpk mppccpta mrs-apdw/ water target(cop

9、y from http:/cbernet.home.cern.ch/cbernet/micromegas)micromegas for tpc012345678光子計測mrs apd(russia)hpk mppc(japan)kek測定器開発室中心開発試験中測定器開発室中心開発試験中t2k実験約実験約60,000使用（使用（2007-2008年）年）1mm100m mmccqeccqeccqeppmpm0 1 2 (gev/c)0 1 2 3 4 (gev/c)0 40 80 120 160 (degree)signal region (s/n 1)(90%cl) 100.608 .)(.)

10、(.0.044 )() (2-. 233103630102910syststatcccoherentccm mn n p p p absorption in the nucleus +0.171, -0.08bg estimation from cc-1p +0.144, * nuclear effect and neutrino interaction (+0.273, -0.253)main systematic uncertainties rein & sehgal : 2.667 x 10-2 15n*16onk+nucl.phys.proc.suppl.159:44-49,2

11、006 nghithardware upgrade is necessary for 1mw.0.75 mwtarget date for new rf system installation.14 iron/sci sandwich trackers are placed with a “cross shape” around the beam axiseach tracker consists of 10 iron plates and 11 scintillator strip planes+ veto planes around each tracker10cm10cmx &

12、y viewson-axis neutrino monitor (ingrid)design-adesign-bor- extruded scintillators- photo-sensor (mppc/sipm)k2k-scibarfgdscinitillation counter: 1cm1cm( better segmentation then k2k)2300mm365mm 2iplastic fgd:15 xy modules(30 layers)iwater fgd:7 xy modules with 6 water layers (2.5cm/layer)inominal scnitillator bar:1cmx1cmx185cmtpc 31 mecalphoto-sensorfiberbarrel ecal moduleia dedicated nc p0 detector. pb(0.6mm) + scintillator (17mm thick) + waterp0dimuon range detector to catch the muon going out of the tpc acceptance. imo