Recent Results from Super-K Kate Scholberg, Duke University June 7, 2005 Delphi, Greece

OUTLINE Super-K Status Atmospheric Neutrino Results -Two-flavor Analyses SK I 'Combined' Analysis L/E Analysis New Combined Finer-Binned Analysis Sterile, Tau Analyses -Three-flavor Analyses Dominant Mass Scale Analysis Analysis with Solar Terms The Future Summary

Super-Kamiokande ~140 collaborators 34 institutions 4 countries

Super-K II: 2003-present Super-K I: ,146 inner (ID)/ 1885 outer(OD) PMTs; 22.5 kt fiducial volume - Solar, atmospheric, proton decay results; K2K I target - Returned to action with 47% ID coverage (acrylic shields), full OD - Nearly same sensitivity as SK I; K2K II target - To turn off October 2005 for full reconstruction Super-K III: Will turn on in April 2006 with full ID PMT coverage - Ready for T2K off-axis beam from J-PARC in 2009

Solar neutrinos with Super-K See Y. Takeuchi's talk in astrophysics session for details of solar oscillation results

Atmospheric Neutrinos: parent energies for subsamples single ring multi ring Fully-contained e-like  -like Partially-contained Upward-going muons stopping throughgoing

Zenith angle distributions SK I Combined 2-Flavor Analysis hep-ex/ downgoing upgoing 1489 live-days, 100 yr MC, 15,000 neutrino events

'Standard' Oscillation Analysis Total 180 bins in zenith angle, momentum Minimizing  2 is equivalent to solving 'Pull method', Fogli et al, hep-ph/ oscillated expectation observed events in bin systematic parameters (36 based on flux, x-scn, selection, reconstruction) fractional change in event rate due to systematic MC statistical and systematic uncertainties estimated uncertainty in  j

Allowed Oscillation Parameters SK I standard combined analysis Best Fit Results:  m 2 = 2.1 x eV 2 sin 2 (2  ) = 1.0 (constrained to physical region)  2 min = 174.8/177 DOF

Resolving the "wiggle" with SK atm 's Poor resolution in L/E (~10's of %) washes it out   hard to distinguish oscillation from more exotic kinds of disappearance (decoherence, decay,..) FC/PC events hep-ex/

Select events for which resolution in L/E is good: (<70%): exclude horizontal, low E, poorly contained, very high E FC single ring  -like FC multi ring  -like PC OD stopping PC OD through-going

"the dip" decoherence Seems to be really wiggling! Similar plot with this selected subset: (~2700 events) Preliminary best-fit osc (favored by >3  ) decay

Best fit using the high-resolution L/E data sample Improves  m 2 resolution a little Best Fit Results:  m 2 = 2.4 x eV 2 sin 2 (2  ) = 1.0 (constrained to physical region)  2 min = 37.9/40 DOF

Single-ring  -like events Results from K2K long-baseline expt Total 107 beam events observed; expect Best Fit Results:  m 2 = 2.8 x eV 2 sin 2 (2  ) = 1.0 (constrained to physical region) Consistent with SK atmospheric  's No-oscillation excluded at >4 

Finer-Binned 2-Flavor Analysis Preliminary - PC events divided into OD stop/OD through-going  2 incorporates Poissonian uncertainties Total of 370 bins in zenith angle, momentum - Finer  -like momentum binning; coarser e-like momentum binning - New FC multi-ring e-like category Combine advantages of standard and L/E analyses

Zenith angle distributions Preliminary

New allowed region with finer-binned analysis Preliminary Best Fit Results:  m 2 = 2.5 x eV 2 sin 2 (2  ) = 1.0 (constrained to physical region)  2 min = 375.2/367 DOF Comparison with 180 bin analysis

Preliminary Allowed regions for the various subsamples 370 bin analysis 180 bin analysis Finer binning for multi-GeV, PC, multi-ring improves the  m 2 constraint

Super-K II results: 1.72 live-years FC/PC 1.67 live-years upmu 60 yr SK II MC Zenith angle distributions Preliminary

Super-K II Oscillation Analysis Preliminary Best Fit Results:  m 2 = 3.1 x eV 2 sin 2 (2  ) = 0.98 (constrained to physical region)  2 min = 395.5/367 DOF L/E Analysis 370 bin combined analysis Best Fit Results:  m 2 = 2.6 x eV 2 sin 2 (2  ) = 1.0 (constrained to physical region)  2 min = 54.8/40 DOF

● NOT pure   e : no up-going e-like excess ● NOT pure   sterile : would expect * up-going NC excess * angular distortion of high E events } not seen Can we see tau appearance explicitly? What flavors are involved in this 2-flavor   x disappearance? (assumed to be    ) Still thinking in 2D:

Tau Appearance in Super-K e or or hadrons Energy Threshold: 3.5 GeV According to MC, expect about 80  's in current sample... but they are hard to distinguish from other multi-ring interaction events Typical MC  event

Select  -like events: (energy, shape, rings, decay electrons) 2 analyses (likelihood and neural network) yield consistent answers Consistent with (expected) slight excess of upgoing  's MC expectation: 79  31  's Neural Network (36%efficiency) From fit to  -like sample: (red hatched) osc param  's

Now, start thinking in 3D... -K MNS mixing matrix atmospheric solar ??? What can we say about the oscillation parameters in a 3-flavor context?

First, consider dominant mass difference scale,  (and  =0) In this approximation, oscillation probabilities described by 3 parameters: m2m2 m3m3 m1m1 m2m2 m1m1 m3m3 solar atmospheric } { Normal Inverted

P(   e ) Normal hierarchy: resonance for neutrinos matter enhancement P(   e ) P(    ) P(    ) P(    ) GeV Look for signature of non-zero  13 in (e.g.) enhancement of e for certain angles and energies

For example: enhancement of upgoing multi-GeV single ring electrons Positive  m 2 Negative  m 2 Null oscillation  m 2 = eV 2 sin 2  23 = 0.5 sin 2  13 = 0.05 SK 20 years Single-ring electrons (2.5<P<5.0GeV) cos 

We can also, in principle, learn about the mass hierarchy by exploiting differences between nus and antinus: For inverted hierarchy, the resonance happens for antineutrinos, not neutrinos Inverted hierarchy: resonance for antineutrinos P(   e )

Multi-ring e-like In water Cherenkov, it's very hard to differentiate between nus & antinus event-by-event... BUT: there are nu vs antinu differences in  and d  /dy, and relative fraction of nus and antinus is different for different subsamples NC + others CC e higher e / e ratio CC e NC + others Single-ring e-like

For example: more enhancement of upgoing multi-GeV e-like multi vs single rings for normal hierarchy Positive  m 2 Negative  m 2 Null oscillation  m 2 = eV 2 sin 2  23 = 0.5 sin 2  13 = 0.05 SK 20 years Single-ring e-like (2.5<P<5.0GeV) Multi-ring e- like(2.5<P<5.0GeV) cos  higher e / e ratio

What do the data show? - use the fine-binned analysis, Poisson-style likelihood - treat inverted and normal hierarchy cases separately Basically, no suspicious looking excesses seen... Multi-GeV e-like events single-ringmulti-ring cos 

Limits Normal hierarchy Inverted hierarchy Best Fit:  2 min = /368 DOF  m 2 =2.5 x eV 2,sin 2   = 0.5, sin 2   = 0.0 Best Fit:  2 min = /368 DOF  m 2 =2.5 x eV 2,sin 2   = 0.525, sin 2   =

Previous analysis ignored 1-2 oscillation parameters... now look at effect of solar oscillation parameters on atm 's at lower energy: (Note: poor pointing) solar : on sin 2  13 = 0 P(   e )

sin 2  23 = 0.5 sin 2  13 = 0.03 solar : on e.g. Peres & Smirnov, hep-ph/ solar interference  13 Consider solar and  13 effects:

sin 2  23 = 0.4 sin 2  23 = 0.5 sin 2  23 = 0.6 m 2 12 = 8.3 x eV 2 m 2 23 = 2.5 x eV 2 sin 2 2 12 = 0.83 sub-GeV e-like Considering just the solar term:  13 =0 Since r~2, get info about octant of  23 in the sub-GeV e flux cos  Example: e.g. Gonzalez-Garcia et al., hep-ph/

Adding solar terms to the 3-flavor analysis  2 –  2 min distribution as a function of sin 2  23 where the other oscillation parameters are chosen to minimize  2 Best-fit : m 2 12 = 8.3 x eV 2 sin 2  12 = 0.29 m 2 23 = 2.5 x eV 2 sin 2  23 = 0.51 (sin 2 2 23 = ) No evidence for deviation from maximal 2-3 mixing Preliminary

T2K: "Tokai to Kamioka" 295 km, <1 GeV 0.75 MW beam, 2.5 degrees off-axis Start 2009 The Future p  140m0m280m2 km295 km on-axis off-axis Near (280m) + Intermediate (2km) detectors + SK

Future: upgraded T2K beam (4MW) and Hyper-K detector

Summary - Atmospheric neutrinos are still oscillating; confirmed by K2K beam; consistent with  appearance - High-resolution L/E analysis gives tighter  m 2 region, confirms sinusoidal oscillation - New combined 2-flavor fine-binned analysis gives best of both worlds: tighter  m 2 and sin 2 2  - SK II results are consistent with SK I - 3-flavor limits: consistent with  13 =0, less stringent than CHOOZ - With solar terms in 3-flavor fit, consistent with maximal 2-3 mixing - Full reconstruction winter 05/06; T2K beam starts 2009 Preliminary

Limit on admixture of sterile