PHYSICS AND ASTRONOMY WITH SHOWERING UPWARD MUONS IN SUPER-KAMIOKANDE

SHANTANU DESAIPh.D Final Oral Examination

December 3rd 2003

Outline of the Talk:� Super-Kamiokande detector PHYSICS � Dataset used and its classification (upward thru + stopping muons)� Subdivision of upward thrugoing muons (showering + non-showering)� Overview of algorithm used to identify upward showering muons� Energy Spectrum of all 3 categories of events� Oscillation Analayis using upward showering muons ASTRONOMY � Overview of astrophysical searches with upward muons� Gamma-ray burst (GRB) and Soft-gamma-ray repeater (SGR) searches� Diffuse flux searches� WIMP searches

~ 40m X 40 m tank containing50 kton of ultra pure water

11146 20-inch PMTs in ID

1885 8-inch PMTs in OD

Water Cherenkov detector

Located 1 km under mountainin a Zn mine in JapanPhase 1 : 1996 - 2001

Super-Kamiokande Detector

Subject of this Thesis = Upward Going Muon Events

µ

S-K

�

Earth

Background from cosmic ray interactionsin atmosphere on opposite hemisphere of earth

Search for signals from astrophysical sources in upward going muons

blown up

Need to go underground to reduce background from cosmic ray muons

10−13

10−12

10−11

10−10

10−9

10−8

10−7

10−6

10−5

10−4

10−3

0 2 4 6 8 10 12 14 16 18

Depth (10 3 hg cm −2 )

Inte

nsity

(cm

−2s−1

sr−1

)

Super−Kamiokande

Soudan 2Minos

IMB

HomestakeGran Sasso

Crouch World Survey, 1987Crookes and Rastin, 1973Bergamasco et al., 1971Stockel, 1969Castagnoli et al., 1965Avan and Avan, 1955Randall and Hazen, 1951Bollinger, 1950Clay and Van Gemert, 1939Wilson, 1938

Iνµ

π,K−muonsπ,K−muons + I

= 2.17x10 −13

νµ

cm −2s−1sr −1

At Super-K depth

µ� Fluxµ�Flux

~ 10 -5

Bugaev et al 98

Upward Going Muons In Super-K

THRU

STOP

Eυ (GeV)

dΦ/d

logE

υ( 1

0-13 c

m-2

s-1

sr-1

)

ThrugoingStopping

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

1 10 102

103

104

105

�E���100GeV

�E���10GeV

Event display of an Upstop Muon

Event Display of Upthru Muon

Upward Muons originally divided into two categories

Upward Thrugoing467 events 1892 events

Non-Showering Showering

Upward Stopping

Muon critical energy in water ~ 1 TeV

Muon energy (GeV)

< d

E/dX

(MeV

cm

2 g-1

) >

Average < dE/dX > from M.C.

Ionization LossRadiative Loss

Total Loss

1

10

10 2

1 10 102

103

104

105

Showering muons

Monte-Carlo dE/dX agrees with theoretical curves

Non-Showering muons

Muon energyloss inwater

(Groom et al 02)

Muon track

dtrack

For each PMT in cone find point of projection along muontrajectory

Calculate avg corrected charge along each 0.5 m along muon track

dtrack

�Qcorri �

For an ionizing muon

<Qcorri

> ~ constant along the

muon track

dtrack

Muon which loses energythrough radiative processesinitiates an electromagneticshower

from e+ e- pairs Extra Cerenkov light

dtrack

�Qcorri�A showering muon shouldshow huge upward spikesalong muon track

Muon track

dtrack

dtrack

Strategy : Apply corrections to PMT charge to account for:� PMT acceptance� Light scattering� Attenuation due to photon travel distance

Cherenkov light

PMT

dwatdpmt

Qcorr

_________________F ()

Qraw

dwat

exp (dwat

/Latten

)=

Latten

= Light attenuation length

The above corrections not enough

Monte-carlo

Distance travelled by light (m)

corr

ecte

d ch

arge

muon length greater than 30 mmuon length between 20 and 30 mmuon length between 10 and 20 mmuon length less than 10 m

0

5

10

15

20

25

30

35

0 5 10 15 20 25 30 35 40

Monte-carlo

Distance travelled by light (m)

corr

ecte

d ch

arge

muon length greater than 30 mmuon length between 20 and 30 mmuon length between 10 and 20 mmuon length less than 10 m

0

5

10

15

20

25

30

35

0 5 10 15 20 25 30 35 40

Light scattering into the cone increases the effective charge asmuon path length increases

Light Scattering Turned Off

Fit the mean charge of an ionizing muon to 2nd order polynomial

Generated Monte-carlo samples with differentenergies using track directions and entry points from downward muon data

Both muons have same entry point and directions

Projected Distance Along Track (m)

Mea

n co

rrec

ted

phot

o-el

ectr

ons

/ 0.5

m

0

10

20

30

40

50

60

70

80

90

0 2 4 6 8 10 12 14 16 18 20Projected Distance Along Track (m)

Mean c

orr

ect

ed p

hoto

-ele

ctro

ns

/ 0.5

m

0

10

20

30

40

50

60

70

80

90

0 2 4 6 8 10 12 14 16 18 20

Muon energy = 20 GeV

Muon energy = 10 TeV

�dE dX ��2.2 MeV cm �dE dX ��8.5 MeV cm

Show Event Display of the 20 Gev muon event with and without correctionsand same for 10 TeV muon

for a ionizing muon as a functionof path-length

For each upward muon event defined a : χ 2

�2��i�3

n 2

���Qcorri� � �Qcorr��2 �Qcorri

2 ��� �Qcorr� q �l ��2 �q �l �2 �

where � �Qcorr ���

3

n 2

�Qcorri ���Qco rr�2

�3

n 2

1��Qco rr�2

q �l ��� �Qcorr�

Event considered showering iff :

and

�2 D.O.F.�25 �� �Qcorr � q�l ���2.0 pe

{ {

Shape Comparison Normalization Comparison

and

�� �Qcorr � q�l ���4.0 peor

Consistency Check:Does the distribution of showering variables agree for data and atmospheric neutrino monte-carlo?

DataMonte-Carlo (no Osc)Monte-Carlo (Osc)

(∆m2 =0.002 sin2 2Θ =1.0)

[ mean qcorr - Q(L) ]

No

of e

vent

s

0

20

40

60

80

100

120

140

160

180

200

-4 -2 0 2 4 6 8 10

log10(χ2)

No

of

eve

nts

DataMonte-Carlo (no Osc)Monte-Carlo (Osc)

(∆m2 =0.002 sin2 2Θ =1.0)

100

200

300

400

500

600

700

800

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

Yes

superscan[shantanu] Tue Mar 25 01:23:07 2003 Showering Upward Muon

Super-KamiokandeRun 2101 Sub 3 Ev 1523996-07-05:01:46:37 0013 dee4 0606

Inner: 0 hits, 0 pE

Outer: 0 hits, 0 pE (in-time)

Trigger ID: 0x0b

D wall: 1690.0 cm

Upward-Going Muon Mode

Charge(pe) >26.723.3-26.720.2-23.317.3-20.214.7-17.312.2-14.710.0-12.2 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

0 500 1000 1500 20000

400

800

1200

1600

2000

0 500 1000 1500 20000

400

800

1200

1600

2000

Times (ns)

EVENT DISPLAY OF AN UPWARD SHOWERING MUON

Showering Detection Efficiency

Efficiency = # of events identified by algorithm as showering # of events with ∆E/∆X > 2.85 MeV/cm

where

Amount of background from non-showers ~ 5%

Ei

Ef}E/ X = (E∆ ∆

i-E

f)/L

Efficiency ~ 75 %

Total of 332 events in upthru dataset

Total of 3129 events in 40 year upthrumu monte-carlo

Lwhere E

i , E

f

are true muon energies frommonte-carlo

Eυ (GeV)

dΦ/d

logE

υ( 1

0-13 c

m-2

s-1

sr-1

)

ShoweringNon-showeringStopping

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

1 10 102

103

104

105

Applied Showering Algorithm to 40 yr. Monte-Carlo

�E���10 GeV

�E���100 GeV

�E���1TeV

3 categories of upward muons seenin Super-K

Angular resolution of Showering thrumus

Angle between precision fit and truth fit

No

of e

vent

s

0

25

50

75

100

125

150

175

200

225

0 1 2 3 4 5 6 7 8 9 10

Angular resolution = 1.3 degrees

�true

� fit

Corresponds to 68 % of total area

Stops : 1.5 degrees Thrugoing: 1.0 degrees

Downward � near horizon could multiple-scatterand appear as upward �

This background from horizontal muons needs to be subtracted from the upward showeringmuon dataset

Muon direction

Our sample not completely background free

MtIkenoyama

Super-K

Mt. Ikenoyama not homogenous and isotropic contamination from thin parts of mountain in datasetPlotted the azimuthal distribution of upward +downward showering muons near horizon

Azimuth distribution of all showering muons

Φ (degrees)

No o

f E

vents

(1) (2) (1)

1

10

10 2

10 3

0 50 100 150 200 250 300 350

Zenith vs Azimuth for showering muons (641.4 days)

Φ (degrees)

cos

Θ

-1

-0.8

-0.6

-0.4

-0.2

0

0 50 100 150 200 250 300 350

60 < � < 240°

23.38 / 15P1 1.785 0.7645P2 1.594 0.7109P3 67.23 10.81

cosΘ

Num

ber o

f Eve

nts Region (1) Φ < 60 , Φ > 240

Region (2) 60 < Φ < 240

10-1

1

10

10 2

10 3

-0.1 -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08

Estimation of Background Subtraction

Nbkgd

= 8 �7 for cos� > -0.1 out of 80 events

Oscillation Probability for a 2-neutrino beam

P(����

������sin�(2)�sin2 [1.27 m2 (eV2) L(km)/E (GeV)]

�������������������������

m2 = m12 - m

22�

sin2(2) = Mixing angle

First smoking gun evidence for neutrino oscillation discoveredin Super-K with m���0.002�sin�!2���1�(Messier 1999)

All upthrumus

cos Θ

Flu

x (

10

-13 c

m-2

s-1

sr-1

)

Observed FluxNull Oscillation

0

0.5

1

1.5

2

2.5

3

3.5

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

Upward Showering Thumus

cos Θ

Flu

x (

10

-13 c

m-2

s-1

sr-1

)

Observed FluxNull Oscillation

0

0.2

0.4

0.6

0.8

1

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

Zenith Angle Distribution of Upward Showering Muons

"Zenith angle distribution of upward showering muonsconsistent with no oscillation as expected

�2 dof �10.8 10�2 dof �23.1 10

10-4

10-3

10-2

10-1

0 0.2 0.4 0.6 0.8 1

68%CL90%CL99%CL

sin22θ

∆m2 (e

V2 )

10-4

10-3

10-2

10-1

0 0.2 0.4 0.6 0.8 1

68%CL90%CL99%CL

sin22θ

∆m2 (e

V2 )

All upthrumusupstopmus

10-4

10-3

10-2

10-1

0 0.2 0.4 0.6 0.8 1

68%CL90%CL99%CL

sin22θ

∆m2 (e

V2 )

showeringupthrumus

Oscillation Analysis with all 3 Datasets

Weights applied to monte-carlo events : Non -Showering Upthrumus : (1+#) Fnonshower

Showering Upthrumus : (1+#) (1+$) Fshower

Stopping Upmus : (1+#) (1+%) Fstop

#, %, $ kept as free parameters

Following terms added to �2

�#�#�2��%�%�

2��$�$�2

where �#�0.22 �%�0.14 �$�0.08

�2��j�1

3

�i�1

10

��F data F MC ���2

10-4

10-3

10-2

10-1

0 0.2 0.4 0.6 0.8 1

68%CL90%CL99%CL

sin22θ

∆m2 (e

V2 )

Null Oscillation : �2 = 47.3 for 30 dofBest fit Oscillation : �2 = 22 for 28 dof

Best fit point

∆ m2= 0.0023sin2 2 = 1

Combined flux of all 3 samples consistent with oscillations

Non-Showering Upmus

Observed FluxNull Oscillation ( α=-0.203, ε=0.069)∆m2 = 2.29e-03 sin2 2Θ =0.986

(α =-0.056 ε = 0.009)

cos Θ

Flux

( 10

-13 c

m-2

s-1

sr-1

)

0

0.5

1

1.5

2

2.5

3

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

Stopping Upmus

cos Θ

Flux

( 10

-13 c

m-2

s-1

sr-1

)Observed Flux

Null Oscillation (α=-0.203 ε=0.069 β = -0.37)

∆m2 = 2.29e-03 sin2 2Θ =0.986(α =-0.056 β = -0.09 ε = 0.009)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

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

Upward Showering Muons

Observed FluxNull Oscillation ( α=-0.203, ε=0.069 γ = 0.05)∆m2 = 2.29e-03 sin2 2Θ =0.986

(α =-0.056 γ = -0.02 ε = 0.009)

cos Θ

Flux

( 10

-13 cm

-2 s-1

sr-1

)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

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

Overview of Astrophysical Searches Done with Upward Muons

WIMP searches from center of Earth, Sun , Galactic Center

Space-time correlations with transient astrophysical sourcessuch as GRBs and SGRs

Diffuse Flux from plane of Galaxy

Point Sources Searches (both known and unknown) &

Sky map distribution of upward showering muons

Angular clustering and bootstrap techniques used to search for point sources in upward muon dataset (Washburn, Clough)

No evidence for point sources in showering upward muon dataset

Upward showering muon sample suited for high energy ν astronomybecause atmospheric neutrino background is reduced

Space-Time correlation studies with transientastrophysical sources like GRBs and SGRs

� t = � 1 day ���5 deg and look for more than 1 upward muon� No such events found

GRBs (~1600 bursts) : astro-ph/0205304

t = � 1000 sec ���5 deg.

Result : 1 event found. Expected Background = 0.9

SGRs (~150 bursts):

t = � 1 day ���5 deg.

Result : 1 event found . Expected Background = 0.7

==> Expected coincidences with SGRs and GRBs consistentwith background

Upward showering muons

Data (1679.6 days)

M.C. (no oscillations) : Normalized by livetime

M.C. with oscillations : Normalized to Data

Galactic latitude (in Degrees)

Numb

er of

Even

ts

0

10

20

30

40

50

60

70

80

90

100

-80 -60 -40 -20 0 20 40 60 80

Upward stopmus in galactic coordinates

Data (1679.6 days)

M.C. w/o oscillations

M.C. with oscillations

Galactic latitude (in Degrees)

Num

ber o

f Eve

nts

0

10

20

30

40

50

60

70

80

90

-80 -60 -40 -20 0 20 40 60 80

Look for � from cosmic rays coming from ISMUpward thru muons in galactic coordinates

Data (1679.6 days)M.C. without oscillationsM.C. with oscillations

Galactic latitude (in Degrees)

Num

ber o

f Eve

nts

0

25

50

75

100

125

150

175

200

225

250

-80 -60 -40 -20 0 20 40 60 80

Galactic Plane

Matter/ Energy Density Budget of the Universe

(WMAP Collaboration 2003)

One possibility for Cold Dark Matter are:Weakly Interacting Massive Particles (WIMPs) (Weinberg & Lee 77)

�Masses in the GeV to TeV energy range�Annihilation cross-sections ~ Electroweak scale�Exist in Supersymmetric theories beyond Standard Model

INDIRECT WIMP SEARCHES

WIMPs orbiting galactic halo

Potential Sources of WIMP annihilation

Earth : Only sensitive to WIMPs with scalar interactionsSun : Mainly sensitive to WIMPs with spin interactionsGalactic Center : WIMP annihilation dueto spike in density distribution near centralblack hole (Gondolo & Silk 99)

� Detector

�+ � � cc , bb, HH, ZZ , tt. W+ W- , �'�(�- - - -

Neutrinos

WIMP speed ~ 220 km/sec WIMP Density ~ 0.3 GeV/cc

Cone half-angle (degrees)

Numb

er of

even

ts

0

5

10

15

20

25

30

35

40

45

50

0 5 10 15 20 25 30

Cone Half-Angle (degrees)

Num

ber o

f eve

nts

0

10

20

30

40

50

60

0 5 10 15 20 25 30

Cone Half-angle (degrees)

Numb

er of

even

ts

0

10

20

30

40

50

60

70

80

0 5 10 15 20 25 30

WIMP Searches with all upward thrugoing muons

Earth Sun

Galactic Center No signaturesof WIMP annihilation

no osc

with osc

data

WIMP Search with Upward Showering Muons

Looked for excess in direction of Earth , Sun and Galactic Center

Earth SunCone Data

0 0.300 0.402 2.10

Atm ν Bgd

3°5°

10°

Cone Data

0 0.10 5° 0 0.30

2 2.30

Atm ν Bkgd

3°

10°

Cone Data

0 0.500 1.202 3.30

Atm ν Bgd

3°5°

10°

Galactic Center No possible signatures of WIMP-induced upward showering muons from Earth, Sun or Galactic Center

Upward Showering muons sensitive to high mass WIMPs

Super-K (all upthrumus)

Super-K (showering upthrums)

Mass of Neutralino (GeV)

Lim

it on

WIM

P-in

duce

d up

war

d m

uons

(cm

-2 s

ec-1

)

10-16

10-15

10-14

10-13

10-12

10-11

10 102

103

104

Super-K (all upthrumus)Super-K (showering upthrumus)

Mass of Neutralino (GeV)

Limits

on

WIM

P-ind

uced

upw

ard

muo

ns (

cm-2

sec-1

)

10-16

10-15

10-14

10-13

10-12

10-11

10 102

103

104

EarthSuper-K (all upthrumus)

Super-K (showering upthrumus)

Mass of Neutralino (GeV)

Lim

it on

WIM

P-in

duce

d up

war

d m

uons

(cm

-2 s

ec-1

)

10-16

10-15

10-14

10-13

10-12

10-11

10 102

103

104

Sun

Galactic Center

Using the flux limits from the Sun and Earth and resultsfrom from Kamionkowski et. al. (1994) allows to compare our results with direct detection WIMP searches using Si, Ge, NaI etc

101 102 10310−43

10−42

10−41

10−40

WIMP Mass (GeV)

WIM

P−

nucl

eon C

ross

−se

ctio

n (

cm2)

Super−KEdelweissCDMSZEPLINDAMA

101 102 10310−39

10−38

10−37

10−36

10−35

10−34

WIMP Mass (GeV)

WIM

P−

Pro

ton C

ross−

Section (

cm

2)

Super−K (1679.6 days)UKDMC NaI from combined Na and IElegant V

We partially rule out the DAMA allowed region Our limits on WIMP-proton spin cross-section ~ 100 times more sensitive than direct detection experiments

Scalar CouplingAxial Vector Coupling

CONCLUSIONS

� A sample of upward through-going muons which loseenergy through bremsstrahlung and other radiative processes has been isolated

� Mean energy of parent neutrinos of upward showering muons ~ 1 TeV

� Zenith angle distribution of only upward showering muonsconsistent with null oscillations. However combination ofall 3 datasets consistent with oscillations

�Tried all possible tricks to search for signatures of highenergy GeV neutrinos from astrophysical sources. Unfortunately no sources found