L/E analysis and constraints on
exotics of the atmospheric
neutrino data from SuperKamiokande
I.Higuchi
for SK collaboration
ICRR
Feb/20/2007

Content• Introduction• SK experiment• L/E oscillation analysis method• L/E oscillation analysis result• L/E oscillation analysis with exotic modelmodel.
• SummaryIntroduction• We
W presentedt d SK-I+II
SK I II combined
bi d L/E νμ ™ ντoscillation analysis result.
• And
A d we presentedt d ttestt off exotic
ti modeld l ((neutrinoti
decoherence, neutrino decay) separately.
• But,
B t neutrinot i decoherencedh(d(decay)) anddoscillation can coexist. We can constrain
decoherence (decay) parameterparameter, if we test L/Eoscillation analysis with exotic models.
• We report the L/E oscillation analysis with exoticmodels.

Super Kamiokande
Super-Kamiokande
1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

SK-I

accident

SK-II reconstruction SK-III• 50kton cylindrical water
Cherenkov detector(22 5kt fiducial vol.)(22.5ktvol )• 1000m underground(2700m water equiv.)

SK-ISK-II• optically separated into
ID and OD

PMT enclosure :Acrylic (front) andFiberglass (back)

11146

Num. of inner detector PMTs

5182

40 %

Photocathod coverageg

19 %SK-I (1489days) + SK-II (804days)

SK-III physics started in July 2006.

Survive probability
N ti
Neutrinooscillation
ill ti :Pμμ

Neutrino decay :Pμμ = (cos2θ + sin2θ x exp(– m L ))22τ E
1Pμμ = 1 – sin22θ x (1 – exp(–γ0 L ))2Eνμ )

Neutrino decoherence :Proob.( νμΔm2L
22= 1 – sini 2θsin2θ i ()Use events with high resolution in L/E

1

The first dip can be observed

08
0.80.6

Æ Direct evidence for oscillations
Æ Strong constraint to oscillation
parameters, especially Δm2 value

04
0.4
0.20E

1

10102

103104L/E (km/GeV)L/E oscillation analysis method
Downward（L=10~100 km）

Zenith angle θDetector

Upwardp（L= up to 13000 km）• We use full data sety )SK-I ((1489days)
SK-II (804days)• Reconstruct flight
length and energy.
• Vary parameters(sin22θ,Δm2,γ0(orm/ )) fit each modelm/τ)),and compare the χ2

Event samples in L/E analysis
Data set:SK-I(1489)
SK-II(804)

FC (tracks are contained inside the ID)

Fully Contained(Eν ~1GeV)
1GeV)

I. Single-ring , μ-like
II. Multi-ring , μ-likePC (deposits visible energy in the OD)

Partially Contained((Eν ~10GeV))

μ-likeClassify PC events using OD charge
I. OD stopping
II OD thII.
throughh goingi

We apply resolution cut.

Reconstruction of E and L
Neutrino flight length

Neutrino energy
104103102

Flight length (km)Eν/Eobserved

2.521.5
10.50Eν
Eobserved
1log10(Eobserved)

Eobserved Æ EνNeutrino energy is reconstructedfrom observed energy using
relations based on MC simulation

10-1 -0.8 -0.6 -0.4 -0.2 00.2 0.4 0.6 0.8

1Zenith angle (cosΘ)

Zenith angle
Æ Flight length

Neutrino flight length is estimatedfrom zenith angle of particle direction

Results of L/E oscillation analysisy• SK-I+IISK I+IIAssuming νμ⇔ντχ2min = 83.9/82 d.o.fat(sin( 22θ,Δm2)=(1.00,2.3x10-3eV2 )χ2osc = 83.9/82 d.o.fχ2dcy = 107.1/82 d.o.f, Δχ2 = 23.2(4.8σ)
χ2dec = 112.5/82 d.o.f, Δχ2 = 27.6(5.3σ)
We exclude neutrino decoherece, decay about 5 σ

oscillation and exotic mode surviveprobabilityνμ⇔ν⇔ τ Oscillation
O ill ti :

Pμμ

Δm2L
2
2
= 1 – sini 2θsin
2θ i ()
EPμμ = sin4θ + cos4θ x exp(–p( m L )τ E+2sin2θ cos2θ x exp(– m L )2τ E
Δm2L×cos()
2Eνμ⇔ντ Oscillation+decoherence : Pμμ = 1 – 1 sin22θ x (1 – exp(– L2EEEγ)
Δ 2LΔmνμ⇔νντ Oscillation
Oscillation+decaydecay :0×cos( 2E ))Results of L/E oscillation analysis
withith ddecoherence
h-21022Δm (eV )• SK-I+IIχ2min = 83.8/80 d.o.f
At (γ0,Δm2,sin22θ)2θ)=(0 GeV2,2.4x10-3eV2,1.00)
35

30

30

25

25

20

20

Allowed limit at 90% C
C.L.:
L:<1.4x10-22
99% C.L.
90% C.L.
68% C.L.

SK-I+IIΔχΔχ2235-3101515101055-4010-4102-32Δm (eV )10-21010010-310-210γ0 (× 10-1-211GeV)

10-310-210γ0 (× 10-1-211GeV)

10

Compare with the published limit
P.R.L. 85.1166(2000)() E.Lisi,, A.Marrone,, D.Montanino• Effects of decoherence
90%C.L. upper
pp limiton the distributions oflepton events as aP.R.L.
This result
function of the zenith-2121 1.4x10-22220(GeV) 2.0x1020x1014x10γangle using SK-I data.

We can improve one orderResults of L/E oscillation analysis
withith ddecay
10

Allowed limit at 90% C.L.:<3 2x10-5<3.2x1022Δm (eV )• SK-I+IIχ2min = 83.8/80 d.o.f
At (m/τ,Δm(m/τ Δm2,coscos2θ)=(0 GeV/km,2.4x10-3eV2,0.5)

-2-3

10

99% C.L.
90% C.L.
68% C.L.
-4

1010-7

10-610-5

10-410m/τ (GeV/km)-310-2Local minimum due toneutrino decay

Prob.(νμ → νμ)2Contour and Δχχ distributioncos2θΔm2m/τ

Best fit

0.50

2.4x10-3

0.0

Local minimum

0.31

2.4x10-3

1.3x10-3

10.8
0.6
0.4
0.2
0110102103Local minimum

L/E (km/GeV)

35

35

ID
Entries
Mean
RMS

60

30

40
51
0.34020.1732

30

50

25

25
40
220

η

Δχ

Δη

2

2

20

30

15

20

10

10

515
10
50 -7
100

10-6

10-5

10-4

10

m/τ (GeV/km)

-3

10-2

0.2

0.3

0.4

0.5
2cos θ

0.6

0.7

0 -4
10

102-32Δm (eV )10-2Compare with the published limit
P.R.L. 82.2640(1999) V.Barger, J.G.Learned,S.Pakvasa,T.J.Wiler• Fit to the L/E
distribution modeled
neutrino decay.
SK I+II, PC• We use SK-I+II
event and highresolution sample
sample.

90%C.L. upper
pplimit
P.R.LThism/τresult
GeV/km 7.8x10
7 8x10-55 3.2x10
3 2x10-55

summary• We reported L/E oscillation analysis withexotics.
• We get chi2 minimum at νμ⇔ντ oscillation.
• SK constrainst i on exotics
ti mode.
dγ0 < 1.4x10-22 GeV at 90% C.L. for decoherecenm/τ < 3.2x10-5 GeV/km at 90% C.L. for decay