Upward Showering Muons
in Super-Kamiokande
Shantanu Desai /Alec Habig
ForSuper-Kamiokande Collaboration

ICRC 2005 PuneUpward Going Muons in Super-K
0.5-1Thrugoing
Stopping

0.4

0.3

0.25

dΦ/dlogEυ( 10-20.35-13-1

THRUcm s sr )

0.45

0.2

0.15

STOP

0.1

0.05
01

10102

10Eυ (GeV)

3104105

Muon Energy loss as a function of Energy
Non-Showering muon Showering Muon

< dE/dX (MeV cm2 g-1) >Total Loss

EiRadiative Loss
Ionization Loss
102Ef

Average < dE/dX > from M.C.

dE/dX = (Ei - Ef)/LDistribution
asymmetricfor each muonenergies

101L

110102103Muon energy (GeV)

104105(Groom et al 03)

Reasonably good agreement of Monte-Carlo with PDG
Aim of this analysis is only to separate a given muon into
showering/non-showering

Corrections to raw PMT charge
Muon track
dwat
PMT

Apply following correction for every PMT in Cherenkov Coneqcorr = qraw dwat exp(dwat/Latten)-------------------------F(θ)

where Latten= Water attenuation length,
dwat = Distance from PMT to point ofprojection to µ track
F(θ) = PMT acceptance + shadowing

Divide the muon track into 50 cm bins. For each bin, calculate
average corrected charge and its statistical error as follows:

Qicorr2i
Q corrN pmt
1q corr
N pmt

N pmt

2q1corr
N 2pmt 1 qraw

where Npmt = No of pmts within the given
projected distance corresponding to each binMuon Energy = 20 GeV
90
80
7060
5040302010002468 10 12 14 16 18 20

Projected Distance Along Track (m)dE/dX = 2.16 MeV/cm

Mean corrected photo-electrons / 0.5 m

Mean corrected photo-electrons / 0.5 m

Corrected Charge Distribution Comparison of ionizing vs showering muon
Muon Energy = 10 TeV
90807060
50403020
10002468 10 12 14 16 18 20

Projected Distance Along Track (m)dE/dX = 8.5 MeV/cm

Both simulated muons have same entry point and direction

Variables used for showering/non-showering separationi 3

Qicorr2Q corr

2Qicorr{2n 2Shape Comparisonn 3

whereQ corr

Qicorr

4n 31and4q l2iQ corr

(Average correctedcharge averaged overentire muon length)

for a ionizing muon as a functionof path-length

Q corrq l{Q corr

2Q icorr

Absolute Corrected Charge Comparison

Difference in averagecorrected charge ofgiven muon – samefor ionzing muon

300

Variables when applied
to 100yr upmu NEUT
Monte-Carloχ2 comparison

200

for data and monte-carlo

Data
M.C.

600

No of events

500
400

100
000.5

11.5

22.5

23log10 (Σ {(dE/dX)i- mean} /dof)

200

3.5

Data
Monte-Carlo180
160
140No of events

12010080∆ comparison

6040for data and monte-carlo

200-4-20246[ mean qcorr - Q(L) ]810

SHOWERING CUT USED
χ2/DOF >40 and ∆ >1.0
2
χOR /DOF>20 and ∆>2.5

2OR χ /DOF >30 and ∆ >2.0

OR χ2 /DOF>50 and ∆>0.5

OR ∆> 4.5
Total no of showering events = 5575 (out of 37301)
in 100 year upmu NEUT Monte-carlo
Efficiency = 71 % where,
Efficiency = No of events Identified by algorithm--------------------------------------------No of events with ∆ E / ∆ X > 2.85 MeV/cm∆ E = Energy deposited by muon in inner detector∆ X = Length of muon in inner detector

NEUTRINO ENERGY SPECTRA
0.5Showering
Non-showering
Stopping

0.4

0.35
0.3

<Eυ> ~ 10 GeV<Eυ> ~ 100 GeV

0.25dΦ/dlogEυ( 10-13-2 -1-1cm s sr )

0.45

0.2

<Eυ> ~ 1 TeV

0.15
0.1

0.05
01

1010210Eυ (GeV)

3104105

Event Display of upward showering muon
Super-Kamiokande
Run 2101 Sub 3 Ev 15239
96-07-05:01:46:370013 dee4 0606
Inner: 10877 hits, 191405 pE
Outer: 249 hits, 863 pE (in-time)
Trigger ID: 0x0b
D wall: 1690.0 cm
Upward-Going Muon Mode

Charge(pe)>26.7
23.3-26.7
20.2-23.3
17.3-20.2
14.7-17.3
12.2-14.7
10.0-12.2
8.0-10.0
6.2- 8.0
4.7- 6.2
3.3- 4.7
2.2- 3.3
1.3- 2.2
0.7- 1.3
0.2- 0.7
< 0.2
2000
1600
1200
800
400
00500

1000

Times (ns)

1500

2000

Angular Resolution of showering muons
Angular resolution of Showering thrumusµfit

350300

No of events

µtrue

400

250
200
150

Shaded region
contains 68 %of total area
Angular resolution = 1.25°

100500012345678910Angle between precision fit and truth fit

Thrugoing muons : Angular resolution ~ 1°
Stopping muons : Angular resolution ~ 1°

Zenith-angle distribution of showering muons
No Oscillation

1000∆m2 = 0.0025 sin2 2Θ =1.00

No of events

800

600

400

200

0-1-0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1

cosΘ

0Showering muons relatively insenstive to oscillation==> For this dataset chi-square for null -oscillation should bevery good fit

Background Subtraction
Applied the showering algorithm to horizontal thrugoing muonwith 0 < cos(θ)< 0.08
Azimuth distribution of all showering muons
(1)

(2)

19.48

(1)

1010

Number of Events

No of Events

10

3

2/ 14
1.702
1.728
65.17

0.88690.7089
10.86

Region (1) Φ < 60 , Φ > 240
Region (2) 60 < Φ < 240

102

10

1

10

1

3P1P2
P3

10050

100

150

200

250

Φ (degrees)

300

350

-1-0.1 -0.08 -0.06 -0.04 -0.02

0cosΘ

0.02 0.04 0.06 0.08

Fit to thin rock zenith angle distribution: f[cos(θ)] = p1+ exp [p2+p3 cos(θ)]

Nbkgd = 8.63 +12-5 for cos(θ)> -0.1

(Asymmetric distribution becauseof bump near horizon)

Showering Muon Oscillation Results
Best-fit (physical region) :χ2 = 4.68 / 7 dof for (∆m2, sin22θ) = (0.0104 eV2, 0.9)
Best-fit (null oscillation) :χ2 = 6.51/9 dof
100

No of showering muons

908070

Zenith angle comparison
at best fit point

6050
4030

Null oscillation
normalized by livetime

20100-1-0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1

cosΘ0

Projections of chi-square distributions
for showering muons
101099% C.L.
90% C.L.
68% C.L.

χ - χ min822442200
106262χ - χ min8

99% C.L.
90% C.L.
68% C.L.

-4

10-32210∆m (eV )

-2

00.2

0.4

0.6

0.8

1

1.2

1.42

sin 2θ

Null oscillation allowed even at 68 % confidence level as expected
for this high energy νµ with mean energy of ~ 1 TeV

Comparison with all upward thrugoing muons
101099% C.L.
90% C.L.
68% C.L.

8

χ - χ min6624222χ - χ min

899% C.L.
90% C.L.
68% C.L.

4

2200

10-4

10-32210-2

00.2∆m (eV )

0.4

0.6

0.8

1

1.2

1.4

2sin 2θ

Best-fit : χ2 = 7.64 / 7 dof for (∆m2, sin22θ) = (0.0024 eV2, 0.96)
Best-fit at null oscillation : χ2 = 19.6/9 dof
Upward thrugoing muons sensitive to neutrino oscillation

CONCLUSIONS
A sample of upward thrugoing muons which lose energy throughradiative processes have been identified.
Mean energy of parent neutrinos of upward showering muons~ 1 TeV.
5575 showering muons in 100yr neut Monte-carlo and 309 eventsin 1679.6 days data
Zenith angle distribution of upward showering muons consistent
with null oscillations
This dataset will now be used for oscillation analysis with all datasetsby providing an extra energy bin at highest energies.
A variety of astrophysical searches with upward showering muons done.
Nothing found. (S. Desai thesis 2003. Also A. Habig poster)