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Results from Super Kamiokande

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Results from Super Kamiokande !!""##$$%%&&##''(())**++'',,$$--""))''..//++00**11//2233"" !!""##$$%%&&""''(())$$**$$%% $$''%%++,,##""--..%%$$..%%//0011,,22%%33""))(($$44""''55,,%%66$$----""++$$22""**$$2277 880044,,%%99''((::,,2277((**;; <<1122((--%%==>>??%%@@AAAABB <<CC//%%)),,,,**((''DD%%""**%%EE""664477$$''::((----,,%%((''%%FFGG Super-Kamiokande Collaboration 140 collaborators from 35 institutes of 5 countries 45675899: Naho Tanimoto 2 Contents Introduction of Super-Kamiokande detector Atmospheric neutrino flavor mixing Nucleon decay search Solar neutrino oscillations Conclusion 45675899: Naho Tanimoto 3 Super-Kamiokande Experiment A 50 kton Water Cherenkov detector 1000m rock overburden (2600m w.e.) 22.5 kton fiducial mass Inner Detector (ID) : 11146 20-inch PMT tubes Outer Detector(OD) : 1885 8-inch PMT tubes Optical separation between inner and outer detector 45675899: Naho Tanimoto 4 More than a Decade of SK SK1 (1996-2001) 11146 inner(ID)/ 1885 outer(OD) PMT's; 40% of ID coverage AApprriill,, 22000066 Solar ν, atmospheric ν, proton decay results; K2K I target SK2 (2003-2005) Recovered 2001 accident with 19% ID coverage (shielded by SSKK33 SSKK22 acrylic covers), full OD Nearly same sensitivity as SK1; K2K II target SK3 (2006-present) During SK3 reconstruction Data taking since July 2006 with full coverage Ready for T2K off-axis beam from 45675899J:-PARC in 2009 Naho Tanimoto 5 SK Event Categories Neutrino observed via charged-current interactions with nuclei in water FC ~1 GeV 1. If lepton has enough energy it will make Cherenkov light FC multi ring ~3 GeV 2. Outgoing Cherenkov light is observed by the PMTs PC stop ~5 GeV 3. Energy and Position (vertex) of the event can be reconstructed PC through ~1~100 GGeeVV 4. Particle ID : e/µ like Up µ stop ~1~100 GGeeVV Up µ through ~1~10000 GGeeVV Up µ shower ~1 TeV 45675899: Naho Tanimoto 6 Atmospheric neutrino results Recent atmospheric neutrino research at SK Search for neutral Q-balls in SK II (Phys. Lett. B 647, 18 (2007)) Observation of the anisotropy of 10 TeV primary cosmic ray nuclei flux with the Super-Kamiokande-I detector (Phys. Rev. D75, 062003 (2007)) A Measurement of Atmospheric Neutrino Flux Consistent with Tau Neutrino Appearance (Phys. Rev. Lett. 97, 171801 (2006)) Search for Diffuse Astrophysical Neutrino Flux Using Ultra-High Energy Upward-Going Muons in Super-Kamiokande I (ApJ. 652,206 (2006)) Three flavor neutrino oscillation analysis of atmospheric neutrinos in Super-Kamiokande (Phys. Rev. D 74, 032002 (2006)) νµ→ντ oscillation is compared with alternative exotic models (sterile neutrino, neutrino decay and neutrino decoherence) 45675899: Naho Tanimoto 7 Atmospheric Neutrinos 1.Primary cosmic ray interaction in the atmosphere 2. Cascade of secondary π, K 3. Decay of secondaries µ Zenith angle θ µ νµ Downward (L=10~100 km) θ νµ ν, ν, Eν : 100MeV ~ 10TeV Flux up/down symmetric - differences in upward and downward going flux is a signal of neutrino Upward physics (L=up to 13000 km) 45675899: Naho Tanimoto 8 Zenith angle distributions (SK1+SK2) νµ;ντ'*#<0%%/&0*2=/&'>"#&'(0&'-*02&? 2$%%'*#<0%%/&0*2 2 2 2 Δm L e-like µ-like Pµ→τ = sin 2θsin (1.27 ) E Sub-GeV elike Sub-GeV µlike Multi-ring elike Multi-ring µlike SK1: 1489days p<400MeV/c SK2: 804days p<400MeV/c s t 23,000 ν's n e v Sub-GeV elike Sub-GeV µlike PC stop PC through e 100MeV-10TeV f o r Upward through- e p>400MeV/c p>400MeV/c b going showering µ um Upward Upward through-going n Multi-GeV elike Multi-GeV µlike stopping µ non-showering µ New <*#θ <*#θ <*#θ <*#θ <*#θ 45675899: Excellent agreement with νµ→ντ oscillatioNnah oh Tyapnimoottho esis 9 Allowed Oscillation Parameters(SK1+SK2) νµ→ ντ 45675899: Naho Tanimoto 10 Tau neutrino appearance (SK1) SK atmospheric ν data favor νµ →ντ oscillations as a dominant source of the deficit of ν µ "# " s ! "# # hadron !"#$"! or Energy Threshold: Typical MC τ event 3.5 GeV !"#$%&' According to MC,expect about 80 τ's in current sample... but they are hard to distinguish from other multi- ring ν interaction events 45675899: Naho Tanimoto 11 Select Tau Neutrino like events (SK1) Two analyses (Likelihood and Neural Network) yield consistent answers A best fit ντ appearance signal (shaded area) 138±48(stat.) +14.8/-31.6(syst.) significance : 2.4σ Consistent with the expected number 2 -3 2 of ντ from MC (∆m =2.4x10 eV ) 78.4±26(sys) 45675899: Naho Tanimoto 12 Does it have to be tau neutrino? LEP experiments : Z decay cross section indicates there are only three active neutrino flavors, Nν=2.992±0.020 If only three flavors of neutrinos, it has to be tau neutrino νµ→νe oscillation does not explain the SK data Sterile neutrino (νs: no electric, strong or weak charge ) is a potential candidate of Atmospheric neutrino disappearance Some theoretical models predict the existence of νs So, Compare νµ→ντ oscillation and νµ→νs oscillation Inside detector : Less NC events During the propagation : Has Matter Effect (νµ→ντ doesn't have) 45675899: Naho Tanimoto 13 Tau neutrino vs Sterile neutrino Preliminary Exclusion level : 7.2σ 45675899: Naho Tanimoto 14 What about admixtures? Admixtures are model dependent SK analysis is based on Fogli et al PRD 63 (053008) 2001 A 2+2 mass hierarchy model Construct a superposition of vs and ντ states → 2 flavor mixing m ν ATM 4 s preliminary m3 ντ LSND ν m µ Solar 2 ν m1 e Sterile mixing portion m ν 4 cos2 ξ sin2 ξ 1 m3 νµ " cos$'% sin $'% " 1 & # $" % $(sin $'% cos$'%%$" % 2 s Allowed sterile neutrino admixture limit at 90% C.L. : sin2 ξ<0.23 45675899: Naho Tanimoto 15 Neutrino disappearance : L/E (SK1+SK2) Survival probability of νµ is a function of L/E for 2 flavor 2 2 2 Δm L oscillation : P(νµ→νµ) = 1 – sin 2θsin ( ) 4E preliminary preliminary MC(w/o osc) Data/MC(w/o osc) Data Best Fit Best fit: ∆m2=2.3x10-3, sin22θ=1.00 2 χ min=83.9/83 d.o.f. 45675899: Naho Tanimoto 16 Alternative models of Neutrino Disappearance What about other possibilities? Neutrino Decay Assuming the dominant component of νµ , i.e., ν2, to be the only unstable state with a lifetime τ0 m 4 4 2 L ν ≈ cosθ ν +sinθ ν , ν ≈ν Pµµ = sin θ + cos θ x exp(– ) µ 2 3 e 1 2τ E Neutrino Decoherence effect induced by new physics 2 1 2 ∆m L Pµµ = 1 – sin 2θ x(1– exp(–γ L) x cos( )) 2 0 2E Oscillation Can test the first dip in L/E Decay Decoherence 45675899: Naho Tanimoto 17 Test of other modes with L/E of SK1+SK2 The data/prediction for 3 models as a function of L/E SK1+SK2 preliminary ) 2 c χ (decoherence)=112.5/82 s Decoherence o 2 d.o.f., ∆χ =27.6 (5.3σ) o n ( 2 C Decay χ (decay)=107.1/82 d.o.f., M / l ∆χ2=23.2 (4.8σ) e d o m : o i t 2 a Oscillation χ (osc)=83.9/82 d.o.f. R Neutrino decoherence and decay models are excluded at ~5σ 45675899: Naho Tanimoto 18 ν osc. and decoherence(decay) coexistence In addition, we compared two models : 1) Neutrino Oscillation 2) Neutrino Oscillation + + Neutrino Decay Neutrino Decoherence -5 γ <1.4x10-22 GeV m/τ0 < 3.2x10 GeV 0 at 90% C.L. at 90% C.L. 99% C.L 99% C.L 90% C.L. 90% C.L. 68% C.L. 68% C.L. -21 γ0(x10 GeV) m/τ0(GeV/s) 45675899: Naho Tanimoto 19 Three flavor oscillation analysis (SK1) 3 flavor mixing looks like this : )) " * " # # $ # ' ( $"% '"% # & $+ % " " "& "& ,)- ,./ )- + " &!* + !& # $ ' # " # (' $ # % *% %& %& "% "% / &/)0$+ % $ %$ ) ) %$ % )- )- $ % $ % # (' $ ( " * %& %& '"& ( # $"& # # " & & atmospheric ??? solar In the full expression of U, we have 6 parameters 2 2 2 2 2 θ12,θ13,θ23, ∆m 12,∆m 23, where ∆m ij ≡ m j-m i, and δCP Open question in neutrino physics : θ13, δCP are nonzero? What is the mass hierarchy? m3 m3 m2 Mass Or m2 m1 m1 (Normal) (Inverted) 45675899: Naho Tanimoto 20 SK approach to these problems are νµ→νe mantle core The effect on P(νµ→νe) for nonzero θ13 can be large. We can look for extra e-like events at high energy as an indication of θ13 SK can not discriminate between ν and ν on an event-by-event basis. However, the amount of e-like excess depends on the magnitude of θ13, and on the sign of the hierarchy. For inverted hierarchy anti-ν's experience this resonance 45675899: Naho Tanimoto 21 Three flavor oscillation Results(SK1) The up-down asymmetry as a function of momentum is consistent with expectation of θ13=0. No significant e-like excess has been seen. Both normal and inverted mass hierarchy hypothesis are tested and both are consistent. Obtained upper limits on θ13 is consistent with CHOOZ limit. SK 90%C.L ∆m<0 ∆m>0 SK 99%C.L. CHOOZ 90%C.L. exclude 45675899: Naho Tanimoto 22 Nucleon Decay Search Past experiments and SK Nucleon Lifetime with have set severe constraints antilepton+meson modes (90%C.L.) on viable GUTs. Minimal SU(5), Minimal SUSY SU(5) p→e+π0 : 8.4x1033yrs are ruled out. New modes are being tested. p→K+ν : 2.3x1033yrs 45675899: Naho Tanimoto 23 n-n oscillation (SK1) Other models of GUTs predict ∆(B-L)=2 Preliminary processes, such as n-n oscillation. Signal MC nN annihilation arising from nn oscillation which occur in the H2O nuclei produce multiple particles. →multi-rings Detection efficiency = 10.4% Atm ν BG Main source of BG is from atm.ν RReejjeecctteedd Observed: 20, Expected BG: 21.31 1.77x1032 yr at 90% C.L.
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