Neutrino Mass Hierarchy Determination with...

Neutrino Mass Hierarchy Determination with PINGU

Ken ClarkUniversity of Toronto

K Clark - NuFACT 2013

IceCube

AMANDA

DeepCore

scattering

DOM: Digital Optical Module

• First need to introduce IceCube

• Instrumented ~1km3 of ice with ~5000 DOMs

• 78 vertical strings, 60 DOMs per string

2


IceCube Events

3


IceCube

X (m)-100 -50 0 50 100 150 200

Y (m

)

-150

-100

-50

0

50

100 IceCube

PINGU Geometry - 26m String Spacing

125m

• 78 Strings

• 125m string spacing

• 17m DOM spacing

• Add 8 strings


• 7m DOM spacing

• Add 20 strings


• 5m DOM spacing10 TeV 1 EeV1 TeV100 GeV10 GeV1 GeV100 MeV

IceCube

10 MeV

4


IceCube Results

• Designed to look for high energy (TeV - PeV) events

• Much success in recent studies at these energies

1.04 + 0.16 PeV 1.14 + 0.17 PeV

5


IceCube

X (m)-100 -50 0 50 100 150 200

Y (m

)

-150

-100

-50

0

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100 IceCube


• 78 Strings


• 17m DOM spacing

• Add 8 strings


• 7m DOM spacing

• Add 20 strings


• 5m DOM spacing10 TeV 1 EeV1 TeV100 GeV10 GeV1 GeV100 MeV

IceCube

10 MeV

6

125m


IceCube + DeepCore

• 78 Strings


• 17m DOM spacing

• Add 8 strings


• 7m DOM spacing

• Add 20 strings


• 5m DOM spacing

X (m)-100 -50 0 50 100 150 200

Y (m

)

-150

-100

-50

0

50

100 IceCubeDeepCore


125m

10 TeV 1 EeV1 TeV100 GeV10 GeV1 GeV100 MeV

IceCube

10 MeV

DeepCore

7

75m


IceCube + DeepCore

• Addition of extra strings in closer proximity lowers the detection threshold energy

• Volumes shown are calculated at trigger level

8


IceCube + DeepCore

• Addition of extra strings in closer proximity lowers the detection threshold energy

• This allows for sensitivity at the energy of an oscillation minimum

9


DeepCore Results

• Approximately 1 year of data analyzed

• High rate in detector provides large event sample

• High energy sample constrains uncertainties in fit

10

Phys. Rev. Lett. 111, 081801 (2013)


• Oscillation parameters extracted

• Very good agreement with world averages

• Possible improvement with more advanced reconstructions and event selection

DeepCore Results

11


IceCube + DeepCore

• 78 Strings


• 17m DOM spacing

• Add 8 strings


• 7m DOM spacing

• Add 20 strings


• 5m DOM spacing

X (m)-100 -50 0 50 100 150 200

Y (m

)

-150

-100

-50

0

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100 IceCubeDeepCore


125m

75m


IceCube

10 MeV

DeepCore

12


X (m)-100 -50 0 50 100 150 200

Y (m

)-150

-100

-50

0

50

100 IceCubeDeepCorePINGU


IceCube + DeepCore + PINGU• 78 Strings


• 17m DOM spacing

• Add 8 strings


• 7m DOM spacing

• Add >=20 strings


• 5m DOM spacing

125m

75m

26m


IceCube

10 MeV

DeepCorePINGU

13


• 9.28 GeV Neutrino, 4.9 GeV muon, 4.5 GeV cascade

IceCube + DeepCore

Improvement with PINGU

14


• 9.28 GeV Neutrino, 4.9 GeV muon, 4.5 GeV cascade

IceCube + DeepCore

Improvement with PINGU

IceCube + DeepCore + PINGU15


PINGU Physics• Many topics opened up by the lowering of

the energy threshold• muon neutrino disappearance• tau neutrino appearance• maximal θ23

• dark matter• neutrino mass hierarchy

16


PINGU Physics• Many topics opened up by the lowering of

the energy threshold• muon neutrino disappearance• tau neutrino appearance• maximal θ23

• dark matter• neutrino mass hierarchy

17


Neutrino Mass Hierarchy• Three flavour

oscillations mean disappearance/appearance of νμ are both important

P⌫µ!⌫µ = 1�

cos

2✓

m13sin

22✓23 ⇥ sin

2

1.27

✓�m

231 +A+ (�m

231)

m

2

◆L

E

�

�sin2✓m13sin22✓23 ⇥ sin2

1.27

✓�m2

31 +A� (�m231)

m

2

◆L

E

�

�sin4✓23sin22✓m13sin

2

1.27(�m2

31)m L

E

�

• Can be used to distinguish mass hieararchy

18


1Length (km)

0 2000 4000 6000 8000 10000 12000

Eart

h D

ensi

ty (g

/cm

^3)

0

2

4

6

8

10

12

14Normal Hierarchy

Inverted Hierarchy

°) with Travel Through the Earth - 10 GeV, 179µν→µνP(

)µν

→µν

P(

00.10.20.30.40.50.60.70.80.91

Why Atmospheric Neutrinos?

• Oscillation probability P(νμ→νμ) directly related to L/E• L measured using angle through the Earth

19


1

1

2

2Length (km)

0 2000 4000 6000 8000 10000 12000

Eart

h D

ensi

ty (g

/cm

^3)

0

2

4

6

8

10

12

14Normal Hierarchy

Inverted Hierarchy


)µν

→µν

P(

00.10.20.30.40.50.60.70.80.91

Length (km)0 1000 2000 3000 4000 5000 6000 7000

Eart

h D

ensi

ty (g

/cm

^3)

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

Normal Hierarchy

Inverted Hierarchy


)µν

→µν

P(

00.10.20.30.40.50.60.70.80.91

1

2

Why Atmospheric Neutrinos?

20


PINGU Significance

i = cos(zenith)j = energy

21

• Atmospheric neutrinos provide a large flux of incoming neutrinos at a range of incoming angles and energies

• Non-resonance MSW effects make up roughly 2/3 of PINGU’s sensitivity as (anti-)neutrinos travel through the mantle

• Parametric resonance occurs for neutrinos traveling through the core to make up the remaining 1/3

• Resonances are due to matter-induced oscillation phase changes

Core


Calculating Significance• Counts in one year are

binned depending on energy and zenith angle

• This includes both νμ and νμ

• There are differences in the number of counts per bin

• These differences create the patterns which give the distinguishability

N IHij �NNH

ijqNNH

ij


Cos(zenith angle)-1 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0

Ener

gy (G

eV)

2

4

6

8

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12

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18

20

200

400

600

800

1000

1200

Counts in PINGU 1 Year - NH

Cos(zenith angle)-1 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0

Ener

gy (G

eV)

2

4

6

8

10

12

14

16

18

20

200

400

600

800

1000

1200

1400Counts in PINGU 1 Year - IH

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Calculating Significance

N IHij �NNH

ijqNNH

ij


Cos(zenith angle)-1 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0

Ener

gy (G

eV)

2

4

6

8

10

12

14

16

18

20

-6

-4

-2

0

2

4

6]1/2Distinguishability Metric [(IH-NH)/NH

23

• As an illustration, a scaled subtraction between hierarchies can be done

• Not the way significance is calculated, but illustrative

• As an example of systematics, look at resolutions

Perfect detector resolution



N IHij �NNH

ijqNNH

ij


Cos(zenith angle)-1 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0

Ener

gy (G

eV)

2

4

6

8

10

12

14

16

18

20

-6

-4

-2

0

2

4





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Zenith resolution: 10° Energy resolution 1 GeV

Cos(zenith angle)-1 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0

Ener

gy (G

eV)

2

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6

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10

12

14

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18

20

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8




N IHij �NNH

ijqNNH

ij


Cos(zenith angle)-1 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0

Ener

gy (G

eV)

2

4

6

8

10

12

14

16

18

20

-6

-4

-2

0

2

4


Cos(zenith angle)-1 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0

Ener

gy (G

eV)

2

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-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8


Cos(zenith angle)-1 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0

Ener

gy (G

eV)

2

4

6

8

10

12

14

16

18

20

-1

-0.5

0

0.5

1

]1/2Distinguishability Metric [(IH-NH)/NH




25

Zenith resolution: 12.5° Energy resolution 3 GeV


PINGU Systematics• Reconstructions are obviously a

significant factor in the hierarchy determination

• Currently using DeepCore algorithms

• New more computationally intensive algorithms may improve resolutions

• Also studying many other sytematics

• θ23, θ13 Δm2atm, δCP

• Atmospheric ν spectrum, efficiency errors, etc.

26

Events with Selection Applied - Energy

Events with Selection Applied - Zenith Angle


PINGU Hierarchy Analysis• For the final result, two different analysis

methods are being pursued• Both rely on the creation of “templates”

from simulated data

27

Cos(zenith angle)-1 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0

(Ene

rgy

(GeV

))10

Log

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

0

20

40

60

80

100

Inverted Hierarchy Template - Event Selection Applied

Cos(zenith angle)-1 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0

(Ene

rgy

(GeV

))10

Log

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

0

20

40

60

80

100

Normal Hierarchy Template - Event Selection Applied


Analysis Method 1• Uses the “Asimov” method using the most likely dataset at

each value of the oscillation parameters

• Calculate the χ2 as a function of these parameters and minimize for Δm2>0 and Δm2<0

28


Analysis Method 2

• Throw many pseudo-experiments varying the bin contents with statistical errors, allow oscillation parameters to be fit

• Generate likelihood ratios, determine significance from these

29

lambdaInvExpInvCosHist_244_tot

Entries 1e+07Mean 15.84RMS 5.527

LLR-40 -20 0 20 40

1

10

210

310

410

510lambdaInvExpInvCosHist_244_tot

Entries 1e+07Mean 15.84RMS 5.527

= 2.44132MΔ(Observed Inv Exp Inv) / (Obs Inv Exp Norm)

lambdaNormExpInvCosHist_244_tot

Entries 1e+07Mean -13.57RMS 5.416





132MΔ

0.2100.2120.2140.2160.2180.2200.2220.2240.2260.2280.2300.2320.2340.2360.2380.2400.2420.2440.2460.2480.2500.2520.2540.2560.2580.2600.2620.2640.2660.2680

1000

2000

3000

4000

5000

310× with Trial Sets Pulled at 0.24413

2MΔBest Likelihood value for

Template:IH Data:IH

Template:NH Data:NH

Template:NH Data:IH

Template:IH Data:NH


Supplemental Methods• Two relatively fast analysis methods used to

study effects of systematics & parameters

30


Hierarchy Sensitivity

31

• Calculated sensitivity shown under several assumptions• Event selection, efficiency and detector geometry varied

• Note that all systematics have not been included here

arXiv: 1306.5846


PINGU Current Activities• Clearly no data to show yet• Studies underway for detailed LoI• Example: choosing a detector geometry

X (m)-100 -50 0 50 100 150 200

Y (m

)

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100PINGU Geometry V6 (Dozier)

IceCube

DeepCore

PINGU (HQE)

PINGU Geometry V6 (Dozier)

32

X (m)-100 -50 0 50 100 150 200

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)

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-50

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DeepCore

PINGU

87 88 89 90 91 92 93

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PINGU Geometry V15 (Ellett)

X (m)-100 -50 0 50 100 150 200

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DeepCore

PINGU

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PINGU Geometry V14 (Domi)


PINGU Advantages• Relatively fast

• Deployment could begin in the 2016-2017 season, takes 2-3 years

• Relatively inexpensive• Start up costs on the order of $10M plus ~$1.25M

per string

• IceCube provides well understood veto • Well understood technology

• IceCube techniques have proven to be robust33


Conclusions

• IceCube and DeepCore have shown the viability of neutrino oscillation physics in the ice

• PINGU will extend the reach of these analyses to lower energies

• Detailed LoI and full proposal will be available soon

34


The IceCube/PINGU Collaboration44 institutions - 4 continents - ~250 Physicists

35

University of Toronto



Oscillograms


Monte Carlo Procedure• Neutrino interactions

modeled with GENIE• Results passed to

Geant4 to create light-generating particles

• Custom GPU software propagates light through detector

38


PINGU Advantages• This is all known

technology

• Drilling, installation can be done “quickly”

• Low cost (relative to other experiments)

• “We know how to do this”

39

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Neutrino Mass Hierarchy Determination with...

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