Takaaki Kajita, ICRR, Univ. of Tokyo NOW2004, Sep 2004

Outline SK Atmospheric neutrino results   , L/E, and 3 flavor analysis K2K    from K2K-I and -II T2K (Future long baseline experiment) Summary Only 2 and 3 flavor neutrino oscillations

SK collaboration: Japan, USA, Korea, Poland

Event classification and statistics Fully Contained (FC) (E ~1GeV) (12180) Partially Contained (PC) (E ~10GeV) (911) Through-going  (E  ~100GeV) (1842) Stopping  (E  ~10GeV) (418) Red: observed number of events in SK-1 (total number = 15351)

Recent improvements New flux based on the 3 dimensional calculation Tuned neutrino interaction MC based on the K2K data 15  37 systematic error terms (S.Moriyama’s talk) 3D 1D   (deg)

Super-K atmospheric neutrino data 1489day FC+PC data day upward going muon data CC e CC 

Binning for 2 flavor oscillation analysis E Single- Ring  Multi- Ring  Up-stop Up-through 18 momentum bins x 10 zenith bins = 180 bins in total Single- Ring e PC Each box has 10 zenith bins Multi- GeV Sub- GeV CC e CC 

Neutrino oscillation parameters 90%C.L.     2  m2=2.1x10 -3,sin 2 2  =1.00 (full paper will be published soon)

oscillation decoherence decay  Further evidence for oscillations  Strong constraint on oscillation parameters, especially  m 2  -like multi-GeV + PC Should observe this dip! SK collab. hep-ex/

Selection criteria Following events are not used: ★ horizontally going events ★ low energy events Select events with high L/E resolution (  (L/E) < 70%) FC single-ring  -like Full oscillation 1/2 oscillation  (L/E)=70% Similar cut for: FC multi-ring  -like, OD stopping PC, and OD through-going PC 2121 FC  -like and 605 PC

L/E distribution MC (no osc.) 1489 days FC+PC  Evidence for oscillatory signature Mostly down-going Mostly up-going Osc. Decay Decoh. Decay and decoherence disfavored at 3.4 and 3.8  levels, respectively.

Allowed neutrino oscillation parameters  2 min =37.9/40  m 2 =2.4x10 -3,sin 2 2  =1.00 (sin 2 2  =1.02,  2 min =37.8/40 d.o.f) 1.9x10 -3 <  m 23 2 < 3.0x10 -3 eV < sin 2 2  23 (90% C.L.)  Stronger constraint on  m 2  Consistent with that of the standard zenith angle analysis

Search for non-zero  13 Electron appearance in the 5 – 10GeV(E ) upward going events. s 2 13=0.05 s 2 13=0.00 null oscillation MC, SK 20yrs Electron appearance 1+multi-ring, e-like, GeV cos  E (GeV) cos  Matter effect (  m 12 2 =0 assumed)

Super-K e-like data Multi-GeV, single-ring e-like Multi-GeV, multi-ring e-like (special) No evidence for excess of upward-going e-like events

Binning for 3flavor analysis E Single- Ring  Multi- Ring  Up-stop Up-through 37 momentum bins x 10 zenith bins = 370 bins in total Multi- Ring e Single- Ring e PC- stop PC- through Same as 2 flavor analysis Different binning from 2 flavor Special in the 3 flavor ana. Fewer number of events per bin Poisson statistics to claculate  2 Multi- GeV Sub- GeV CC e CC 

3 flavor analysis from Super-K Normal prelim. sin 2  13 sin 2  23 sin 2  13 m2m2

3 flavor analysis from Super-K Inverted prelim. sin 2  13 m2m2 sin 2  23 sin 2  13 No evidence for non-zero  13 (No information on the mass hierarchy)

Studies in progress…. Search for tau neutrino interactions Oscillation analysis with the solar terms Simulated  interaction Event rate = 1/kton/year Only upward going Statistical estimate of the  interactions P.Lipari NOON sub-GeV e-like events Peres, Smirnov NPB 680 (2004) 479 Also, M.Maltoni, this meeting, hep-ph/

SK-II atmospheric neutrino data DATA MC (no oscillation, normalized by live time) Live time FC + PC days Upward going  days MC (oscillation,  m 2 =2.1×10 -3 eV 2, normalized by live time) SK-II event Preliminary!

K2K Collaboration 250km JAPAN, KOREA, U.S.A., POLAND, CANADA, ITALY, FRANCE, SPAIN, SWITZERLAND, RUSSIA More details: K.Kaneyuki’s talk

K2K Analysis Overview Near detectors #, p  and    (E )near KEK Observation # and E  rec. Expectation # and E  rec. (sin 2 2 ,  m 2 ) SK Far/Near Ratio  (E )far int. MC Far/Near Ratio E  (GeV) beam MC w/ PION Monitor 12GeV PS (8.9×10 19 POT for Analysis)

Near detectors 1KT Water Cherenkov Detector (1KT) Scintillating-fiber/Water sandwich Detector (SciFi) Scintillator Bar Detector (SciBar) after 2003 Muon Range Detector (MRD) Muon range detector

Front detector measurements:  momentum and angular distributions   (deg.) 090 p  (MeV/c) kton water Cherenkov Also, measurements by SciFi, SciBar and MRD detectors. Prediction of the number of events( ) and spectrum at SK. QE 11 NC Dis Coh 

Event selection in Super-Kamiokande T SK T spill GPS SK TOF=0.83msec 108 events obs’d Decay electron cut E vis > 20MeV No activity in outer detector Event vertex in fiducial volume E vis > 30MeV Analysis time window  500  sec  5  sec T DIFF. (s) events exp’d

Summary of K2K-SK events K2KDATAMC FC 22.5kt ring  -like e-like 98.8 Multi Ring preliminary K2K I+II

K2K energy spectrum (based on single-ring  -like events) MC normalization: number of events E rec [GeV] Number of events Deficit of events MC (no osc.) MC (osc.) preliminary

Best fit values. sin 2 2  1.53  m 2 = 2.12  eV 2 Best fit values in the physical region. sin 2 2  1.00  m 2 = 2.73  eV 2  logL=0.64 Best fit oscillation parameters sin 2 2  =1.53 can occurr due to a a statistical fluctuation with 14.4% probability. Toy MC sin 2 2 m2m % preliminary 1.53

Allowed parameter region m 2 [eV 2 ] sin 2 2 preliminary Best fit values (in the physical region) sin 2 2  = 1.00  m 2 [eV 2 ] = 2.7   m 2 =(1.7~3.5)×10 -3 eV 2 (90% sin 2 2  =1.0 K2K SK(zenith) SK (L/E) 90%CL

K2K Super-Kamiokande 250km J-PARC JAERI Collaboration (at present): Canada, China, France, Italy, Japan, Korea, Poland, Russia, Spain, Switzerland, UK, USA T2K

T2K main physics goals Discovery of non-zero  13 Precise measurement of sin 2 2  23 and  m 23 2 (Discovery of non maximal  23 ?) Discovery of non-zero CP phase 1st phase 2nd phase If  13 ≠0 observed

J-PARC Facility Nuclear and Particle Experimental Facility Materials and Life Science Experimental Facility Neutrino to Kamiokande Linac (350m) 3 GeV Synchrotron (25 Hz, 1MW) Nuclear Transmutation 50 GeV Synchrotron (0.75 MW) J-PARC = Japan Proton Accelerator Research Complex Under construction, expected completion (Phase-I)= end 2007 LINAC 3GeV 50GeV dipole magnets 50GeV

T2K neutrino facility Near detectors (280m, and 2km(not approved yet) To SK T2KK2K E(GeV)50 12 Int.(10 12 ppp) 3306 Rate(Hz) Power(MW) OA3° OA0° OA2° OA2.5° Off axis beam facility

Measurement of  m 2 and sin 2 2  23 Data sample: SK Monte Carlo, Fully-contained single- ring, muon-like events. Event fraction Typical JHF neutrino energy Important to run the experiment with low energy beam. π π E from E  and 

~ OA 2.5 deg. ~ Reconstructed neutrino energy distribution No oscillation reconstructed E (GeV) non-QE  m 2 = 2.5 x10 -3 eV 2 Quasi Elastic reconstructed E (GeV)

Precise measurement of  23,  m 2 23 Assumed systematic errors normalization non-qe/qe ratio E scale Spectrum shape Spectrum width ( 5%) ( 1%) (20%) ( 5%)  (  m 2 23 ) <1×10 -4 eV 2  (sin 2 2  23 )~0.01 True  m 23 2 (10 -3 eV 2 )

 13 Present status: BG (NC  0 ….) Signal for non- zero  13 (   e ) sin 2  13 Allowed

Measurement of   e sin 2 2  13  (CC+NC)Beam e Osc’d e Signal+BG Expected signal for CHOO Z limit reconstructed E (GeV) exp’d signal+BG total BG  BG Number of events  m 2 (eV 2 ) sin 2 2  13  BG=10% Updated More details: K.Kaneyuki’s talk

T2K Phase-II ★ 0.77 → 4 MW beam power ★～ 1 Mton detector (Hyper-Kamiokande) CP Violation 10 6 events (both  and anti-  )

Assumptions Solid line: w/ matter Dashed line: w/o matter (not updated to the most recent solar parameters)

sin 2 2  13 =0.1  m 31 <0  m 31 >0 90%C.L. stat only 90%C.L. stat+2% syst. 3  stat only 3  stat+2% syst. # of e - events including BG # of e + events including BG CP phase Expected CP violation signal (example) Neutrino run=2years, anti-neutrino run=6.8years, 4MW, 0.54Mton fid. Vol.

3  CP sensitivity no BG signal stat only (signal+BG) stat only stat+2%syst. stat+5%syst. stat+10%syst. CHOOZ excluded sin 2 2  13  m 31 2 ~3x10 -3 eV 2 JHF-I: No indication for sin 2 2θ 13 3  CP sensitivity : |  |>20 o for sin 2 2  13 >0.01 with 2% syst. sin 2 2  13 sin 

Beam Transfer line from 3GeV to Material and Life science Facility) Decay Volume ~110m OA2 o OA3 o Target Station ~15m Dump ~10m Neutrino facility construction Construction started Expected completion: early 2009

Present atmospheric neutrino data from SK are nicely explained by    oscillations with;  m 2 =1.9 – 3.0 × eV 2 sin 2 2  > 0.90 (SK L/E analysis) Recent L/E analysis has shown evidence for “oscillatory” signature. No sub-dominant oscillation seen yet. K2K has confirmed neutrino oscillations using the accelerator beam. Neutrino oscillation results from K2K are in good agreement with the SK results. T2K, a precision neutrino oscillation experiment, will start in If non-zero  13 is observed in T2K phase-I, we would like to proceed to T2K phase-II to measure the CP phase.

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