Y Itow Atmospheric neutrino results from SuperKamiokande TAUP

Y. Itow, Atmospheric neutrino results from Super-Kamiokande TAUP 07 13/09/2007 Atmospheric neutrino results from Super-Kamiokande Yoshitaka Itow Solar-Terrestrial Environment Laboratory, Nagoya University for Super-Kamiokande Collaboration

Y. Itow, Atmospheric neutrino results from Super-Kamiokande TAUP 07 13/09/2007 Menu Introduction l Standard neutrino oscillation analysis l ¡ ¡ ¡ l Exploring exotic mode ¡ ¡ ¡ l 2 flavor oscillation results in zenith angle nt appearance results Subdominant oscillation driven by solar terms Ma. Va. N (Mass Varying Neutrino) scenario Neutrino decay / decoherence in L/E Sterile neutrino admixture Status of SK-Ⅲ and future

Y. Itow, Atmospheric neutrino results from Super-Kamiokande TAUP 07 13/09/2007 Super-Kamiokande detector 42 m Ø 50 kt water Cherenkov Ø 1000 m underground Ø ID viewd by 11176 PMT Ø 2 m thick OD for veto Ø Fiducial mass 22. 5 kt Operation since Apr 1996 39. 3 m

Y. Itow, Atmospheric neutrino results from Super-Kamiokande 10 years of Super-Kamiokande 1996. 4 Start data taking 1998 Evidence of atmospheric n oscillation (SK) SK-I 1999. 6 K 2 K started 2001 Evidence of solar n oscillation (SNO+SK) 2001. 7 data taking was stopped for detector upgrade 2001. 11 Accident partial reconstruction 2002. 10 data taking was resumed SK-II 2005 Confirm n oscillation by accelerator n (K 2 K) 2005. 10 data taking was stopped for full reconstruction SK-III 2006. 7 data taking was resumed TAUP 07 13/09/2007

Y. Itow, Atmospheric neutrino results from Super-Kamiokande nm-nt oscillation results TAUP 07 13/09/2007

Atmospheric n categories at SK Y. Itow, Atmospheric neutrino results from Super-Kamiokande n FC n Stopping m PC m TAUP 07 13/09/2007 Through going m m n Energy spectrum of n for each event category up-stop m up-thru m

Y. Itow, Atmospheric neutrino results from Super-Kamiokande TAUP 07 13/09/2007 Up-showering m l. Upgoing through muon sample is separated into “showering” or “non-showering” 68% n to thru-m res. • 1. 25 o (showering, this fig) • 1. 0 o (non-showering)

Y. Itow, Atmospheric neutrino results from Super-Kamiokande TAUP 07 13/09/2007 Zenith Angle Distributions (SK-I + SK-II) P<400 Me. V/c P>400 Me. V/c Livetime • SK-I 1489 d (FCPC) 1646 d (Upmu) • SK-II 804 d (FCPC) 828 d(Upmu) m-like e-like All distributions agree with oscillated expectations

Y. Itow, Atmospheric neutrino results from Super-Kamiokande 2 flavor oscillation analysis TAUP 07 13/09/2007 sin 22 q=1. 0 Dm 2 (e. V 2) Best Fit: Dm 2 = 2. 5 x 10 -3 e. V 2 sin 2 2 q = 1. 00 c 2 = 839. 7 / 755 dof (18%) Dm 2 =(1. 9~3. 1) x 10 -3 e. V 2 sin 2 2 q > 0. 93 @ 90% CL Dm 2=2. 5 x 10 -3 e. V 2 sin 22 q

Y. Itow, Atmospheric neutrino results from Super-Kamiokande nt appearance search t-like selection; efft=43%, S/N=5% multi ring t nt decay-e TAUP 07 13/09/2007 in cc t-enhanced sample

Y. Itow, Atmospheric neutrino results from Super-Kamiokande nt appearance search TAUP 07 13/09/2007 zenith angle distribution of t enrich sample Ntotal(cosq)=a. Ntau+b. NBKG Tau excess t enrich sample is consistent with nm-nt oscillation • a (tau normalization) = 1. 76 • b (BKG normalization) = 0. 9 • c 2/dof=7. 6/8 =16. 3/9 assuming no tau result: • 　fitted t excess 59. 6 ± 20. 7 14. 8 • 　total t excess 138 ± 48 ± 31. 6 　(signal eff. = 43. 1%) • expected 78. 4 ± 26 (syst. ) NN result • fitted t excess 52. 3 ± 18. 7 • total t excess 134 ± 48 ± (signal eff. =39. 0%) • expected 78. 4 ± 27 (syst. ) 16 27. 2

Y. Itow, Atmospheric neutrino results from Super-Kamiokande Oscillation with solar term and determination of octant of q 23 TAUP 07 13/09/2007

Y. Itow, Atmospheric neutrino results from Super-Kamiokande TAUP 07 13/09/2007 Subdominant oscillation w/ solar term in e-like events O. L. G. Peres and A. Yu. Smirnov, hep-ph/0309312 Since simple two flavor oscillations depend on sin 22 q 23. octant of q 23 ( q 23 < 45 o or > 45 o ) degenerates. l LMA parameters , i. e. , (Dm 212 =(7. 4~9. 2)× 10 -5 , tan 2 q 12 =0. 28 -0. 58) can contribute to low energy atmospheric ne in subdominant oscillations l P(ne ne) P(ne nm) = P(nm P(ne nt) = P(nt = 1 – P 2 ne) = cos 2 q 23 P 2 sin 2 ne) = q 23 P 2 c 223 : s 223 n 2 s 212 : n 1 ne c 212 Dm 212 nm nt P 2 : 2 n transition prob. ne nm , t in matter driven by Dm 212 P 2 = r cos 2 q 23 P 2 ne decrease rate by ne oscillation : 1 – P(ne ne) = ne increase rate by nm oscillation : r P(nm ne) cos 2 q 23 = 0. 5 @ q 23=45 o , r = F 0(nm) / F 0(ne) ~ 2 (for low energy n)

Y. Itow, Atmospheric neutrino results from Super-Kamiokande TAUP 07 13/09/2007 Sub-Ge. V e-like zenith angle X : zenith angle Y : N_e (3 flavor) / N_e (2 flavor full-mixing) Sub-Ge. V e-like Pe : 100~400 Me. V/c cos q sin 2 q 23 = 0. 4 sin 2 q 23 = 0. 5 sin 2 q 23 = 0. 6 Pe : 400~1330 Me. V/c cos q Dm 212 = 8. 3 x 10 -5 e. V 2 Dm 223 = 2. 5 x 10 -3 e. V 2 sin 2 2 q 12 = 0. 83

Y. Itow, Atmospheric neutrino results from Super-Kamiokande TAUP 07 13/09/2007 Result of sin 2 q 23 determination (SK-I + SK-II) Assuming sin 2 q 13 = 0 c 2 – c 2 min distribution as a function of sin 2 q 23 where the other oscillation parameters are chosen to minimize c 2 Solar terms off : The 1 -2 parameters (Dm 212 , sin 2 q 12) are fixed at zero. best-fit : sin 2 q 23 = 0. 50 Solar terms on : Pr eli mi na The 1 -2 parameters are scanned. best-fit : sin 2 q 23 = 0. 52 (sin 2 2 q 23 = 0. 9984) ry w/o 1 -2 parameters w 1 -2 parameters No evidence for the deviation of sin 2 q 23 from 0. 5.

Y. Itow, Atmospheric neutrino results from Super-Kamiokande TAUP 07 13/09/2007 Constraint for exotic scenarios

Y. Itow, Atmospheric neutrino results from Super-Kamiokande TAUP 07 13/09/2007 Ma. Va. N (Mass Varying Neutrino) model Neutrino dark energy scenario l Relic neutrinos of which masses varied by ambient neutrino density (A. Nelson et al. 2004) l Possibly their masses also varied by matter density or electron density beyond the MSW effect Check additional matter effect in atmospheric data • Dm 2→Dm 2×(re/r 0)n (r 0=1. 0 mol/cm 3) mass varying with electron denstiy • 2 flavor Zenith angle analysis • assuming sin 22 q=1. 0 • SK-I dataset

Y. Itow, Atmospheric neutrino results from Super-Kamiokande Result for Ma. Va. N-type matter effect n vs Dm 2 for Ma. Va. N model TAUP 07 13/09/2007 Dm 2 c 2 -c 2 min (Dm 2=1. 95 x 10 -3) n Best fit : Dm 2=1. 95× 10 -3 e. V 2 n=-0. 03 c 2=172. 2/178 dof c 2 -c 2 min n c 2 -c 2 min (n=-0. 03) Ma. Va. N type models tested are disfavored Dm 2

Y. Itow, Atmospheric neutrino results from Super-Kamiokande L/E oscillation analysis Neutrino oscillation : Neutrino decay : Neutrino decoherence : TAUP 07 13/09/2007 Dm 2 L d. o. f 2( Pmm == 183. 9/82 – sin 22 qsin ) osc E m L 2 q x exp(– c 2 dcy d. o. f, Dc 2 = 23. 2 (4. 8σ) Pmm ==107. 1/82 (cos 2 q + sin ))2 SK-I+II 2 t E 2 22 q x (1 L )) c dec Dc– 2 exp(–g = 27. 6 (5. 3σ) Pmm= =112. 5/82 1 – 1 sind. o. f, 0 2 E c 2 survival probability data decoherence decay oscillation

Y. Itow, Atmospheric neutrino results from Super-Kamiokande 1 sin 22 q x (1 – exp(–g 0 L ) E 2 Dm 2 L 　　　×cos( )) 2 E Pmm = 1 – TAUP 07 13/09/2007 Pmm = sin 4 q + cos 4 q x exp(– m L ) t E m L) 2 t E +2 sin 2 q cos 2 q x exp(– Dm 2 L ×cos( ) oscillation+decay 2 E Dm 2 (e. V 2) oscillation+decoherence g 0 (× 10 -21 Ge. V) c 2 min = 83. 8/81 d. o. f (g 0, Dm 2, sin 22 q)= (0 Ge. V, 2. 4 x 10 -3 e. V 2, 1. 0) g 0 <1. 4 x 10 -22 Ge. V (90%C. L. ) m/t (Ge. V/km) c 2 min = 83. 8/81 d. o. f (m/t, Dm 2, cos 2 q) = (0 Ge. V/km, 2. 4 x 10 -3 e. V 2, 0. 5) m/t <3. 2 x 10 -5 Ge. V/km (90%C. L. )

Y. Itow, Atmospheric neutrino results from Super-Kamiokande Sterile neutrino admixture TAUP 07 13/09/2007 Based on Fogli et al PRD 63 (2001) 053008 for 2+2 mass hierarchy, 4 flavor mixing can be converted into two 2 -flavor mixings sin 2 x vs Dm 2 24. 5% of sterile neutrino admixture is allowed at 90% C. L.

Y. Itow, Atmospheric neutrino results from Super-Kamiokande SK-Ⅲ　status and future TAUP 07 13/09/2007

Y. Itow, Atmospheric neutrino results from Super-Kamiokande Super. Kamiokande-III • Full 20”PMT with acrylic cover and FRP case • Top and bottom outer detector (OD) is optically separated from barrel OD • Calibration system and sources are improved. TAUP 07 13/09/2007

Y. Itow, Atmospheric neutrino results from Super-Kamiokande Zenith angle distribution @ SK-III Pr Sub-Ge. V e-like p<400 Me. V/c Sub-Ge. V m-like p<400 Me. V/c eli TAUP 07 13/09/2007 data : Aug/2006 -Mar/2007 ina 166 days ry m MC w/o oscillation SK-III data Sub-Ge. V e-like p>400 Me. V/c Sub-Ge. V m-like p>400 Me. V/c Multi-Ge. V e-like Multi-Ge. V m-like +PC events/day SK-III FC 8. 31± 0. 22 PC 0. 57± 0. 06 SK-III start the data taking and analysis. zenith angle dependence is also observed in SK-III SK-II 8. 22± 0. 10 0. 54± 0. 03

Y. Itow, Atmospheric neutrino results from Super-Kamiokande TAUP 07 13/09/2007 New feature of SK-III : Outer Detector (OD) segmentation Wall and endcaps of OD are optically separated. less light creeps around the detector corner Easy reduction of “Conner Clipper muons ” Benefit for PC and upgoing muon analyses

Y. Itow, Atmospheric neutrino results from Super-Kamiokande TAUP 07 13/09/2007 Toward SK-Ⅳ　New electronics development Will be installed in 2008 (before T 2 K) ¡ Based on QTC + TDC chip ¡ “Record all hits” policy ¡ Wide dynamic range (<1000 p. e. ) ¡ Via fast Ethernet readout ¡ Possible complicated and intelligent trigger l Impact for atm n physics ¡ increased m-e decay tagging efficiency ¡ challenge for neutron tagging (2. 2 Me. V g) l Ethernet daughter board QTC TDC

Y. Itow, Atmospheric neutrino results from Super-Kamiokande Summary TAUP 07 13/09/2007 l 2 flavor zenith angle analysis Best fit: (Dm 2, sin 22 q)=(2. 5 x 10 -3 e. V 2, 1. 00) 1. 9 x 10 -3<Dm 2<3. 1 x 10 -3 e. V 2, sin 22 q>0. 93 at 90%C. L. l t appearance t enriched sample is consistent with nm-nt oscillation excess 138± 48± 14. 8 31. 6 expected 78. 4± 26 (syst. ) l Subdominant oscillation w/ solar term So far no measurable deviation of sin 2 q 23 from 0. 5 l Survey of exotic modes No Ma. Va. Ns, n decay, decoherence or sterile scenarios l SK-III status and future Analysis started well. New electronics coming next year before T 2 K !