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ニュートリノ物理 発展と動向

ニュートリノ物理 発展と動向. What do we know today? Solar Neutrino results (SK & SNO) First direct observation of oscillation in solar n Atmospheric neutrino results Atmospheric n deficiency : n m n t LSND and KARMEN More than 3 neutrinos? Present status of K2K What should be (shall be) done next

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ニュートリノ物理 発展と動向

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  1. ニュートリノ物理発展と動向 • What do we know today? • Solar Neutrino results (SK & SNO) • First direct observation of oscillationin solar n • Atmospheric neutrino results • Atmospheric n deficiency : nmnt • LSND and KARMEN • More than 3 neutrinos? • Present status of K2K • What should be (shall be) done next • Conclusion ２００２年１月１６日 ＠国際高等研究所 京都大学大学院理学研究科 西川公一郎

  2. 3 GenerationsMNS matrix • 3 angles and 1 phase propagation solar ne : Dm2 <10-4eV2no n3 reactor ne : (Chooze, Pal-Verde) Ue3 ~ small atm. nm : Dm2 >10-3eV2n3and n1, n2

  3. Measurements at Dm2>10-3eV2(L/E ~ several 100 (km/GeV)) q23, q13, Dm223~Dm213>>Dm212 Three generation ? mixing angle mass difference

  4. Solar neutrinone = n1, n2  nm, nt ? • Standard Solar Model (SSM) and experiments • New SNO results • Super-Kamiokande update to 1286 days • Summary of the status

  5. http://www.sns.ias.edu/~jnb/ Sources of Solar Neutrinos SNO Each experimentis seeing different sources Standard Solar Modelrelates different kinds of experiments

  6. Solar Neutrino Experiments(as ofn2000) +1.4 8.1 -1.1 +8 75 -7 Target Data / SSM (BP2000) ・ Homestake 37Cl 0.32±0.03 ・ Kamiokande e- (water) 0.54±0.07 ・ SAGE 71Ga 0.58±0.06 ・ GALLEX+GNO 71Ga 0.57±0.05 ・ SK e- (water) 0.465±0.015 Be  0 B  0.5 then….no need of osc. +9 +0.20 129 1.0 SNU SNU -7 -0.16 74 ±7 0.54±0.07 0.47±0.02 2.56 ±0.23 Homestake SuperK Kamioka SAGE GALLEX (+GNO) 37Cl H2O Ga 7Be pp, pep Experiments Theory CNO 8B

  7. Measurement of 8B (SK and SNO) • SK ne + e  ne + e CC : NC =6:1 (1) • forward peaked • SNO ne + d  e + p + p CC (2) ne + e ne + e CC : NC =6:1 • (1)-(2) NC event rate due to 8B • should be constant for oscillation among active neutrinos • 8B Flux measurement with neutral current interaction • Confirm SSM (Be, B  pp chain = solarluminescence) • Flux (deduced from NC) – Flux (deduced from CC) • = Non ne components • SSM independent evidence of oscillation

  8. New SNO results • Teff=6.75 Mev • No large spectrum distortion • Charged current : ( Q=1.44MeV) ne + D p + p + e (CC) • electron scattering : n+ e  e + n (ES)

  9. SK + SNO combined [x106/cm2/s] SNO CC = 1.750.15 SK ES = 2.320.09 CC =e ES =e +0.154, , = 3.691.13 X = 5.440.99(total active 8B neutrino flux) (SSM = 5.05+1.01/-0.81) SK

  10. 1km(2700mwe) 3km 2km Mozumi Atotsu Super Kamiokande 41.4m Outer detector 1867 of 8” PMT Ikeno-yama Kamioka, Gifu 50kton stainless steel tank 39.3m Inner detector 11146 of 20” PMT

  11. Direction to the Sun n e- qsun May 31, 1996 - Oct.6, 2000 1258 days Ee = 5.0 - 20 MeV ~18500 solarn events (14.7 events/day) COSqsun +0.08 8B flux : 2.32  0.03 [x 106 /cm2/sec] -0.07 Data 0.005 +0.016 = 0.451 SSM(BP2000) -0.013 (using Ortiz et al. spectrum shape(nucl-ex/0003006))

  12. Oscillation parameters based on flux ofHomestake, GALLEX, SAGE and SK only ne has n+e CC ne n2 ne→nm(nt ) 99% C.L. n1 r rc

  13. n oscillation in solar neutrino solar neutrino spectrum Small Mixing angle solution Spectral shape distortion P(ne → ne) Night Large Mixing solution Day/night difference Day Low Day/night in pp n Just-so Seasonal effect, spectral distortion Day/night, spectrum with higher precision

  14. Day/Night Effectregeneration through the earth nm (Night-Day) (Night+Day)/2 ne Earth density:r=5g/cm2 (average),13(at core) Affect to oscillations for Dm2 = 10-6 - 10-4 eV2 1% 2% 10% 80% slight negative N-D = 0.033 0.022(stat.)  (sys.) 0.013 0.012 (N+D)/2

  15. Spectrum shape comparison (0.75, 6.310-11eV2) Justso (6.310-3, 510-6eV2) SMA (0.8, 3.210-5eV2) LMA Bad fit for SMA and Just-so solutions. uncertainties of absolute energy scale, energy resolution, 8B spectrum shape

  16. Excluded by SK zenith angle spectrum at 95%C.L. Allowed by global fit (Cl + Ga + SK flux) at 95%C.L. • nenm(t) • LMA prefered Dm2(eV2) nenm(t) nensterile 95%CL sin22q

  17. Fogli et.al. hep-ph/0106247

  18. Time variation of the flux, seasonal c2 for eccentricity: 3.9 / 7 d.o.f. (79% C.L.) Sunspot # (c2 for flat: 8.1 / 7 d.o.f. (32% C.L.) ) No magnetic field dep. No distance dep. (Just-so)

  19. KamLAND http://www.awa.tohoku.ac.jp/KamLAND Kamioka Liquid scintillator Anti-Neutrino Detector • 1000m3 liquid scintillator • 3000m3 oil+water shield • 1300 17-inch PMTs +600 20-inch PMTs • Anti-ne from reactors (L~170km) • Detect e+ from ne + p  e+ + n (Eth = 1.8 MeV)

  20. KamLAND: sensitivity What(3) From K.Inoue (Tohoku Univ.)

  21. Conclusion on solar neutrinos • There is non-electron neutrinos in solar n - neutrino oscillation! • SSM is OK within 20% • Just-so, LOW, and SMA are disfavored • 93 % C.L. by SK zenith-spectrum analysis for ne→nm(nt ) oscillations. • Sterile is disfavored with 95% C.L. by zenith-spectrum. • Energy spectrum is consistent with flat. • day/night difference is 3.3±2.2 +1.3/-1.2 %. • Large angle solution : testable in KAMLAND • Also by Borexino

  22. Event topology FC PC Initial neutrino energy spectrum Stopping muons FC + PC Through-going muons stopping muons Interaction in the rock through-going muons

  23. Zenith angle distribution (Soudan 2) HiRes events (106.3±14.7 nm, 132.8±13.4 ne) log(L/En) Decay excluded by 2 s cos Q

  24. Zenith angle distribution No oscillation Δm2=2.5x10-3 sin22θ=1.0 (best fit)

  25. nm-nt allowed region FC + PC + up-through + up-stop + Multi-ring χ2min=142.1/152dof @(Δm2,sin22θ)=(2.5x10-3,1.0)

  26. nmnt v.s. nmns C.C. N.C. nt X ○ nsXX • NC in the earth ( matter effect ) • PC, up through μ(high energy)  FC (low energy) • ntCC interaction in SK detector t appearance

  27. matter effect in the earth sin22θ ( -cos2θ)2+sin22θ sin22θ～1, Eν>20GeV  sin22θm≪1 sin22θm = 2VEν Δm2 νμーνs νμーνs νμーντ νμーντ up through going μ <Eν>～100GeV vertical/horizontal ratio PC, Evis>5GeV <Eν>～25GeV up/down ratio

  28. nmnt v.s. nmns νμーνs νμーνs νμーντ νμーντ data νμーνs νμーντ NC enrigh multi ring event up/down ratio up through μ vertical/horizontal ratio high energy PC up/down ratio

  29. nmntappearance study CC nt interaction ντ + N → τ + N’ +π+π... mnn, enn, n+hadrons(p,p,....) Many hadrons are produced. t enriched sample Optimized by using only downward going events. compare upward going data and MC. +8 - 11 43±17 42% 103±41 # of obs. τ efficiency # of τ (eff. corrected) νμ-ντ with ντCC νμ-ντ w/o ντCC +18 - 26 • ～2σ excess of τ-like events. • Data are consistent with νμ-ντ oscillation • with ντCC.

  30. Summary of atmospheric neutrino observation • Oscillation parameters for nm nt : Dm2 = 1.6 ~ 3.6 x 10-3 eV2, sin22q > 0.90 (90%CL) • Decay scenario is disfavored with > 2sfor ldcy>>losc and ldcy<<losc • nm ns is strongly disfavored • Excess from t leptons: 1.5 ~ 2s • Future • Implement 3D flux calculations • Study more on t-lepton production • Study on the mixed final state nt+ ns

  31. LSND and KARMEN Stopping p only p+decay p-absorbed in nuclei ne+p→e++n n+A→A’+g 

  32. LSND-Karmen-Nomad comparison Small Dm2 region remains

  33. n mass - oscillationsallowed regions LSND, if true, more than 3 neutrinos ? No sign in solar and atmospheric neutrino obs.

  34. K2K( Testing atmospheric observation with accelerator neutrino beam) • Distance and direction fixed neutrino energy (En) • Neutrino beam just after birth • 99%nm (decay volume) L=250km

  35. Bird’s Eye Neutrino Beam Line

  36. Spectrum Distortion at Off axis(4 mrad) (MC) 1 mradian accuracy is more than enough

  37. stability pm＋n m-monitor ２００ｍ １ｃｈ＝５ｃｍ 　　＝０．２５ mrad. <1mrad. +1mrad. -1mrad.

  38. 300m from target Fine Grained Detector Near neutrino detector

  39. Neutrino Beam Direction(MRDprofile) Fitted center x: 1±5cm y: －10±4cm Centered within sys. err. of 20cm SK direction (0.7mrad). 400cm near det. 標的 300m x, x q

  40. Stability of Spectrum Muon Energy of MRD events Muon Energy of 1kton events

  41. K2K Results(June ‘99 – July ‘01) • Number of events • 1 kton water Chrenkov detector  SK almost counting experiment • NC/CC, spectrum shape, interaction model errors almost cancell • Spectrum distortion • non-QE , NC must be subtracted

  42. GPS SK Events Tspill TSK TOF~1msec No Decay-e HE Trig. Evis cut (30MeV) No act. in OD(fully contained) Exp’ed Atm n BG <10-3 in 1.5ms window 56 in fid. vol. -0.2<TSK-TSpill-TOF<1.3msec 1msec

  43. Dominant Systematic Errors • uncertainty of far-near ratio (~7%) and • uncertainty of 1kt fiducial volume (~4%).

  44. MC w/o osc. Reconstructed En and muon directionFully contained 1-ring m-like (22.5kt) Note: Dm2=310-3 eV2 corresponds to 600 MeV En Need to estimate syst. err.

  45. Summary of K2K • Accumulated 4.5x1019POT @ SK from Jun ’99 to July ’01. (1.0 1020 protons in 2004) • Neutrino beam is well under control Can extrapolate spectrum and flux from Near to Far • # of fully contained events in fiducial volume @ SK Observed: 56, Expected with null oscillation 80 Probability of null oscillation < 3% • Spectrum analysis, especially improving low energy region, just started • Pion production measurements @ CERN (HARP) • Upgrade in summer 2003 +7.3 -8.0

  46. Atmospheric neutrinos • Where (m2 =1.6·10-3 ~ 4·10-3 eV2 ,sin22q >0.89) • Most likely nmnt • Solar neutrinos • LMA likely Large q12 ,Dm212 ~10-5: CPV asym. can be large • Reactor neutrinos • sin22q13<0.1 for atmospheric Dm2 region • K2K • Decrease over 250km of ~1GeV neutrino • Spectrum distortion • Minos, MiniBooNE, CGN, Kamland • Oscillation pattern, ntappearance, LSND, LMA • What is the best bet for the next step ?

  47. Final goal (my own view) • Our own existence ? • (near) GUTs scale physics • Mass-Interaction : mixing (q13<<q12,q23or q13<q12,q23?) • Small neutrino mass • Existence of CP-violation in lepton sector (lepto-genesis) • Baryon number non-conservation • Very massive detector

  48. CPV in Kaon system was discovered just below Adair’s measurement • CP phase is large in K,B (Jarlskog factor is small) • No theorist predicted large mixing q23 • No strict prediction on q13 , d • 14 order of magnitude extrapolation for proton decay prediction • One order of magnitude improvements are worth the effort ! • Major discoveries may be around the corner

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