IC22 extraterrestrial cascades search-unblinding proposal

Joanna Kiryluk, LBNL

05/06/2009

1. Filtering && Data and Monte Carlo comparisons

2. Extraterrestrial Flux Sensitivities

3. Summary

+

4. Backup slides

11

Cascade Pole Filter: LineFit Velocity < 0.25 and Tensor of Inertia Evalratio > 0.109

Level3:Zenith>1.27 && (TrackLlh logl - CscdLlhVertex negLlh) > -16.2Zenith>1.27 && (TrackLlh logl - CscdLlhVertex negLlh) > -16.2

Level4: Level4: Contained events filter: Contained events filter: Events must start inside a fiducial volumeEvents must start inside a fiducial volume

Level5+6Level5+6Cleaning tails ….Cleaning tails ….

Level2Level2

Data BurnData Burn

Event Selection (shown previously) Event Selection (shown previously)

Level 2-6 Cuts description && more details in backup slides pages: 25-45Level 2-6 Cuts description && more details in backup slides pages: 25-45 22

Cut LevelCut Level

Bg/SignalBg/Signal

Background reduction vs cut level - SummaryBackground reduction vs cut level - Summary

11triggertrigger L2 L4 L6L2 L4 L6

After Level6:After Level6: N(Bg)/N(Signal) ~ 10 N(Bg)/N(Signal) ~ 1033

N(Signal) ~ 160 events in 240 days (EN(Signal) ~ 160 events in 240 days (E-2-2)) 33

Level>=4: running out of bg MC statistics

Cascade Filter levels comparison: Data vs MC

Level 2 Level4 Level6Level 2 Level4 Level6

NChannelsNChannelsExcess in dataExcess in data

44

Cascade Filter levels comparison: Data vs MC Level 2 Level4 Level6Level 2 Level4 Level6

CO

GX

Shapes (COGX and COGY) ~ consistent

Ra

tes

[Hz]

Cascade Pole Filter

CO

GY

55

Data/MCData/MC

Rate problem: above AND below dust layerRate problem: above AND below dust layer

Cascade Filter : Data vs MC (1)

Level 2 Level4 Level6Level 2 Level4 Level6

Cascade Filter levels comparison: Data vs MC C

OG

Z

66

Cut LevelCut Level

TriggerTriggerCascadeCascadePoleFilterPoleFilter

11

After Level6:After Level6: Factor of ~3 discrepancy between Factor of ~3 discrepancy betweenCorsika and experimental rates (bg rate ~10Corsika and experimental rates (bg rate ~10 -2-2 Hz) Hz)

Data/Corsika Rates Ratio vs cut levelData/Corsika Rates Ratio vs cut level

77

fill-ratio= Nr of Hit Doms / Nr of All Doms within a sphere

MeanMeanxx

CscdLlhVertexCscdLlhVertex

Level7: Background reduction using hit topology: Fill-ratio (Doug Rutledge’s module)

distribution of distance between

hit DOM and reconstructed vertex

(for each event)MeanDistanceMeanDistance

xx R=R=22*MeanDistance*MeanDistance

Center= CscdLlhVertexCenter= CscdLlhVertexExample: Example: Fill-ratio=2/10 = 0.2Fill-ratio=2/10 = 0.2

Bad DOMs excludedBad DOMs excluded 88

NuE Corsika Data 10% Level7 cutBelow dust layer

NuE Corsika Data 10% Level7 cutAbove dust layer

Fill-Ratio vs SphereRadius (Level7): Data vs MC

Agreement between data and bg MC in shape above dust layer,Agreement between data and bg MC in shape above dust layer, Different shape in data and corsika below dust layer:Different shape in data and corsika below dust layer: Depth dependent cuts based on Data! Depth dependent cuts based on Data!

99

Cut LevelCut Level

Bg/SignalBg/Signal

No data @Level 7No data @Level 7 2 corsika events@Level7 2 corsika events@Level7

Background reduction vs cut level - SummaryBackground reduction vs cut level - Summary

11

1010

Example of surviving corsika eventExample of surviving corsika event

After Level7 && NCh>50 : After Level7 && NCh>50 : 56 signal events56 signal eventsFor 240 daysFor 240 days

2 events corsika2 events corsika(corresponds to (corresponds to 10+2.8=13 events in 10+2.8=13 events in 240 days)240 days)

No dataNo data

1111

Energy Reconstruction: final cut (Level8) Energy Reconstruction: final cut (Level8) CscdLlh energy reconstruction settings: S. Lafebre && B. Fox (PSU)

Two distributions: depth dependence not build-in to pandel phit-Two distributions: depth dependence not build-in to pandel phit-nohit (uses Bulk ice). Thus cannot cut on RecoEnergy without nohit (uses Bulk ice). Thus cannot cut on RecoEnergy without making a depth dependent correction ~ +/-0.4making a depth dependent correction ~ +/-0.4

NuENuE

Log(TrueEn) - Log(RecoEn)Log(TrueEn) - Log(RecoEn)

TopTopBottomBottom

Log(RecoEn)Log(RecoEn)

1212

Ab

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Ab

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NuE RecoEnNuE RecoEnNuE TrueEnNuE TrueEn

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After RecoEnergy CorrectionAfter RecoEnergy CorrectionBefore RecoEnergy CorrectionBefore RecoEnergy Correction

1313

Below dust layer:Below dust layer: Above dust layer:Above dust layer:

Signal Signal ee (True)Energy distribution after final (Level8) cuts (True)Energy distribution after final (Level8) cuts

Mean=5.26Mean=5.26Mean=5.23Mean=5.23

Log(TrueEnergy)Log(TrueEnergy)Log(TrueEnergy)Log(TrueEnergy)

Uniform energy range for top and bottom parts of the detectorUniform energy range for top and bottom parts of the detector

MC 182 TeV e

Level8 cut: Log(RecoEn_corrected)>4.2Level8 cut: Log(RecoEn_corrected)>4.2 - not optimized, due to limited bg MC statistics- not optimized, due to limited bg MC statisticsAfter final (Level8) cut, 0 events from the burn sample and corsika remainAfter final (Level8) cut, 0 events from the burn sample and corsika remain

1414

Position and Energy resolutions Position and Energy resolutions After Level8 cut on log(E_reco)After Level8 cut on log(E_reco)

1515

Below dust: Below dust:

Above dust: Above dust: Rms=0.26Rms=0.26

Rms=0.31Rms=0.31Lo

g(T

rueE

n) -

Log

(Rec

oEn)

Log(

Tru

eEn)

- L

og(R

ecoE

n)Lo

g(T

rueE

n) -

Log

(Rec

oEn)

Log(

Tru

eEn)

- L

og(R

ecoE

n)

Log(TrueEn) - Log(RecoEn)Log(TrueEn) - Log(RecoEn)

Log(TrueEn) -Log(RecoEn)Log(TrueEn) -Log(RecoEn)

Log(TrueEn) Log(TrueEn)

Log(TrueEn) Log(TrueEn)

Energy Resolution (Level8)Energy Resolution (Level8)

1616

Position resolutions at L8 (NuE MC) for CscdLlhVertex

diff CscdLlh Vertex

X Mean=0.1RMS=10.9

Y Mean=-0.9RMS=10.9

Z Mean=-12.RMS=26.

TrueY-RecoYTrueX-RecoX

TrueZ-RecoZ

1717

ExpectedExpected event upper limit event upper limit And flux limit after unblindingAnd flux limit after unblinding

For unblinding we propose to use For unblinding we propose to use all the cuts ( Level <=8 )all the cuts ( Level <=8 )

1818

<mu90> for bg=0.0

Event upper limit

<mu90> for bg=10

If much better bg MC statistics were available then we could estimate bg precisely and If much better bg MC statistics were available then we could estimate bg precisely and do bg subtraction to get a better limit (Fieldman-Cousins) do bg subtraction to get a better limit (Fieldman-Cousins) Since we don’t have enough MC, we can assume all observed events (after Since we don’t have enough MC, we can assume all observed events (after unblinding) are signal and set an upper limit for the mean of Poisson variable given unblinding) are signal and set an upper limit for the mean of Poisson variable given N_observed events in the absence of background [1-CL=Sum_0^Nobs PN_observed events in the absence of background [1-CL=Sum_0^Nobs Pxx(n) ](n) ]

240 days of livetime and CL=90%

Conservative limit!Conservative limit![ Used e.g. in HEP experiments [ Used e.g. in HEP experiments to set limits on rare decays to set limits on rare decays branching ratios ] branching ratios ]

1919

E2xlimit =MRFx10-6 [GeV s-1 sr-1 cm-2]E2xlimit range: 7 x (10-8 - 10-7) [GeV s-1 sr-1 cm-2] (conservative limit )assuming n_observed events < 20 after unblinding range depends on n_observed after unblinding If much better MC statistics were available then we could do bg subtraction to get If much better MC statistics were available then we could do bg subtraction to get a better limit - but we don’t. Use limit assuming no bg.a better limit - but we don’t. Use limit assuming no bg. “problem” if significantly more events observed after unblinding

MRF to estimate flux limit expectations after unblinding

<mu90>/nsignal for bg=0.0

<mu90>/nsignal for bg=10

2020

Summary1. Data and MC rate discrepancy: increases with cut level. Shapes agree better than rates, bigger discrepancy below dust level

(e.g. fill-ratio) 2. Final cuts based on data (burn sample), but also on (a few) bg MC

events with long-er effective lifetime than data (insufficient bg Monte Carlo statistics)

3. Will use a conservative method to estimate flux limit assuming no background contribution (no precise estimate of background contribution thus no background subtraction method)

3. Final energy range: ~20 TeV to ~1PeV (Mean ~ 160 TeV)4. Expected results after unblinding: E2xlimit range: 7 x (10-8 - 10-7) [GeV s-1 sr-1 cm-2] if n_observed < 20 after unblinding

[ Flux limit will depend on number of observed events after all cuts after unblinding. Problem if “large” number of events observed]

• ICRC writeup (analysis description) available on the wiki page:

http://wiki.icecube.wisc.edu/index.php/Papers_for_ICRC-2009

Ready to unblind 2121

BACKUP SLIDESBACKUP SLIDES

1. Data - burn sample (24 days)

2. Monte Carlo samples:a) Signal: electron neutrino: - dataset 1736 and 1739 NuGen E

-2 spectrum, log10(E)= 1.6 - 10.0 Total = 3.5 M IC22 triggered eventsb) Background MC - Corsika (single muon) dataset 1540 (unweighted) dataset 1541 (weighted)

Total= 280 M IC22 triggered events

- Corsika (coincident muon) dataset 1567 (unweighted) - Corsika (tri-coincident muon) dataset 1569 (unweighted) much smaller samples: 1.8M IC22 triggered events / set

Data and MC Samples

100k files generated100k files generatedHuge effort, production @multiple sitesHuge effort, production @multiple sites

InIce SMT trigger

Rat

e [H

z]R

ate

[Hz]

Time [Mjd]

PoleCascade filter

Trigger rate: temperature variationData: 515 Hz to 615 Hz MC: 565 HzData/MC AgreementData/MC Agreement

CascadeFilter rate:Data: 18 Hz to 22 HzMC: 14 HzData/MC ~ 1.3 -1.6Data/MC ~ 1.3 -1.6

CascadeFilter/Trigger rate ratio: Data: 0.032-0.036 (stable)MC: 0.025

07/01/07 03/16/08

Experimental rates taken from the Monitoring page

Trigger and PoleCascadeFilter rates

Cascade Pole Filter: data vs MC

LineFit velocityLineFit velocity ToI evalratioToI evalratio

P. Toale && M. D’Agostino filter proposal: LineFit Velocity < 0.25 and Tensor of Inertia Evalratio > 0.109

L2/Trigger Bg reduction = 0.025L2/Trigger Bg reduction = 0.025 Signal fraction = 0.71 Signal fraction = 0.71

Cascade Filter (Level3 FINAL): Data vs MC Common cut for atmospheric and extraterrestrial analyseCommon cut for atmospheric and extraterrestrial analyseModule Module CscdL2Filter (Michelangelo D’Agostino UCB) (Michelangelo D’Agostino UCB) Zenith>1.27 && (TrackLlh logl - CscdLlhVertex negLlh) > -16.2 Zenith>1.27 && (TrackLlh logl - CscdLlhVertex negLlh) > -16.2

This is a This is a loose cut for extraterrestrial analysisloose cut for extraterrestrial analysis

Level3 optimalization for Level3 optimalization for Extraterrestrial analysis Extraterrestrial analysis

Later it was decided to use looser cuts Later it was decided to use looser cuts And keep the same i3 files for atmospheric And keep the same i3 files for atmospheric And extraterrestrial analyses And extraterrestrial analyses

Zenith [rad]

Data: Excess of ‘cascade-like’ events with small values of reconstructed Zenith angle and small values of RllhTrack/RllhCscd are for COGZ at the bottom of IC22

Cascade Filter Level2: Data vs MC (5)

RllhTrack / RllhCscd

Corsika (single muons): Events with Zenith>1.4 rad are misreconstructed downgoing “leading” muons

Reconstruction results from TrackLlh and CscdLlh algorithms

Zen

ith

RllhTrack / RllhCscd

Signal eCorsika backgroundData (run=109831)

Level3 Cuts: Reconstruction Results at Level2

TrackLlh Zenith vs RllhTrack/RllhCscd

Zenith Cut [rad]

Sqrt(N_bg) / N_Signal vs Zenith Cut in RllhRatio bins:

RllhRatio=0.8

RllhRatio=0.9

RllhRatio=1.0

RllhRatio=1.025

1.4 1.70.8

N_Signal / sqrt(N_bg) maximum for: Zenith> 1.4 rad and RllhRatio > 1.0

(proposed cuts for this analysis at level3)

Level3 cuts optimalisation

Find the best combination of cuts on Zenith and

RllhTrack/RllhCscd by minimizing sqrt(N_bg)/N_sig (using Monte Carlo only)

assuming 240 days of livetime and signal flux(es) = 1.0 x 10-6(7) E-2 .

Extraterrestrial e: Level3 Cuts Optimalisation

Result: Level3 cut = Zenith> 1.4 rad && RllhTrack/RllhCscd > 1.0

4 TeV

1.0x10^6 E-2 flux N_sig(Level3) N_sig(Level2)

Event display: Level2 Cascade Filter events

NCh= 293 Nstrings= 19Reco: TrackLlh Zenith= 0.59 rad Rllh-track/Rllh-cscd ratio= 0.71

2 example events from run=109831(real data)

NCh= 57 Nstrings= 8Reco: TrackLlh Zenith= 0.62 rad Rllh-track/Rllh-cscd ratio= 0.83

Cascade Pole Filter

Improvement in Rate vs COGZ (Corsika and Data)

After Level3 cuts

Cascade Filter Level3 proposed cut: Data vs MC

Cascade Pole Filter After Level3 cuts

Improvement in #channels distribution (Corsika and Data)

Cascade Filter Level3 proposed cut: Data vs MC

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Level2Level2

Data BurnData Burn

Events must start inside Fiducial volume

Cascade Filter (Level4):contained event filter (data)

ContainedFilterModule (Steve Movit PSU)ContainedFilterModule (Steve Movit PSU)

+ 8 DOMs top layer of the detector + 8 DOMs top layer of the detector

Geometrical effect:For cascades inside fiductial volume filter efficiency is 100%

Before (Level3) and After (Level4) contained Filter

Filter most efficient at lowest energies

Log10(MCPrimaryEnergy) Log10(MCPrimaryEnergy)TruePosX

Cascade Filter (Level4):contained event filter (signal MC)

L4/L2 Bg reduction = 0.012L4/L2 Bg reduction = 0.012 Signal fraction = 0.13Signal fraction = 0.13

PosX distributions in PosY bins PosX distributions in PosY bins

Sum Sum

Extraterrestrial e: Summary of Statistics (MC)

@Trigger Level , Cascade Filter Level and Analysis-Level4 Assumed: Livetime= 240 days and signal flux = 1.0 x 10-6 E-2

(A) InIce SMT trigger

(B)

Cascade Pole Filter (L2)

B/A (C)L3+L4

L3+Contained Filter

C/B

Nsig (MC) 2.7x103 1.8x103 0.71 240 0.13

Nbg (MC)

(data)

1.2x1010

1.3x1010

2.7x108

4.6x108

0.025

0.035

3.2x106

6.3x106

0.012

0.014

Nbg (MC)

Nsig (data)

4.1x106

4.8x106

1.5x105

2.5x105

1.3x104

2.6x104

Nbg(data)

Nbg(mc)

1.1 1.7 2.0

Run=109930 3-muon event

T1-T2[ns]

Cut=5 s

First hit from the earliest muon starts in the middle of the detector, thus passing contained filter cut

long tailUp to 60 s

T2

T1

NChannel =152T1-T2=13 s

Cascade Filter (Level5): Data vs MC (1)

Zenith>1.2rad Bg: Misreconstructed downgoing muon

32-iteration track reconstruction

Zenith>1.2rad downgoing muons

Nchannels NCh>=20Nchannels NCh>=20 (loose cut) (loose cut)

Cascade Filter (Level5): Data vs MC (2)

running out of MC statisticsrunning out of MC statistics

L5/L4 Bg reduction = 0.07L5/L4 Bg reduction = 0.07 Signal fraction = 0.69Signal fraction = 0.69

Zenith>1.2rad for (Single) Corsika: Misreconstructed downgoing muons(96% of L5a NuE events survive)

32-iteration track reconstruction

Level 5b) downgoing muons Zenith angle cut

Examples of ‘Cascade’ like events with highest Nchannel multiplicity at Level5

After Level5After Level5

Reconstructed Cascade vertex and COGX (COGY) less than 60 m apart:

Cascade Filter (Level6): Data vs MC (1)

XX YY

Cascade Filter (Level6): Data vs MC (2)

Time(FirstTrack)-Track(Secondtrack) > -1000ns Time(FirstTrack)-Track(Secondtrack) > -1000ns (Double muon reconstruction)(Double muon reconstruction)

Reduced Llh Track/Cascade > 0.95Reduced Llh Track/Cascade > 0.95

L6/L5 Bg reduction = 0.37L6/L5 Bg reduction = 0.37 Signal fraction = 0.98Signal fraction = 0.98

CscdReducedLlh=(negLlh/(nHits + unHitContribution - freeParams));

ToI evalratioToI evalratio LineFit velocityLineFit velocity

Variables not usable for further cutsVariables not usable for further cuts

COGXCOGX COGYCOGY

COGZCOGZ

After Level7&&NCh>50: tightening the cutsAfter Level7&&NCh>50: tightening the cuts

56 signal events56 signal eventsFor 240 daysFor 240 days 2 events corsika2 events corsika(corresponds to (corresponds to 10+2.8 evts 240d )10+2.8 evts 240d ) No dataNo data

After Level7 - tightening the cutsAfter Level7 - tightening the cuts

56 signal events56 signal eventsFor 240 daysFor 240 days 2 events corsika2 events corsika(corresponds to (corresponds to 10+2.8 evts 240d )10+2.8 evts 240d ) No dataNo data

Variables not usable for futher cutsVariables not usable for futher cuts

After Level7&&NCh>50: tightening the cutsAfter Level7&&NCh>50: tightening the cuts

NChNCh

NStringsNStrings

Llh DiffLlh Diff

EventLengthEventLength

Extraterrestrial e: Summary of Statistics (MC)@ L4,L5 and L6

Assumed: Livetime= 240 days and signal flux = 1.0 x 10-6 E-2

MC (C) L4

L3+Contained filter

(D) L5

T<5s &&

Zenith>=1.2 &&

NCh>=20

(E) L6= L5 &&dT(double )< -1000ns &&

RllhTrack/Cscd <0.9 &&

|CscdPosX-COGX|<60m&&

|CscdPosY-COGY|<60m

(F) L7

Fill ratio

+Nch>50

L8

Nsig (MC) 240 165 161 56 43

Nbg (MC)

data

3.2x106

6.3x106

2.3x105

4.9x105

8.6x104

27.7x104

13 (2 evts)

0

0

0

Nbg

Nsig

1.3x104

2.6x104

1.4x103

3.0x103

5.3x102

17 x102

0.23

0

0

0

Nbg(data)

Nbg(mc)

2.0 2.1 3.2 No data

Low mc

MC underestimate rates: Factor of 2 (3) at L4 (6)L7&&L8 Insufficient MC Large uncertaintiesL7&&L8 Insufficient MC Large uncertainties

‘‘Baloon’ events (at Level2) Baloon’ events (at Level2)

-small fraction observed mostly at the top part small fraction observed mostly at the top part of the detector (not x-y symmetric!) of the detector (not x-y symmetric!) - removed by fiducial volume cuts - removed by fiducial volume cuts

Dom#

Dom#

Dom# 6 Dom# 7

Dom# 6 Dom# 7

String 73

String 39

Depth dependence!

String 73

String 39

Q [p.e.]

Q [p.e.]

<Q

> [p

.e.]

<Q

> [p

.e.]

Cascade Filter Level2: Total charge per Dom vs depth Shown at the Spring 2008 Collaboration meeting

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

<Q

tot>

String Position Y[m]

<Q

tot>

String Position X[m]

Mean total charge per Dom versus String Position X(Y) e.g. for DOM# 3 (i.e. at fixed depth)

string73

Discrepancy between data and MC Problem caused by small fraction of events with large charge. Effect more pronounced at the top of IC22

<Q

tot>

String Position X[m]

Good agreement between data and MC

StringPosition Y[m]

Cascade Filter Level2: Data vs MC (4a)

Mean total charge per Dom versus String Position X(Y), e.g. for DOM# 55 (i.e. at fixed depth)

<Q

tot>

NCh=32 Nstrings=6

<Q

tot>

DOM#

Example of (rare) event (run=109831) with large charge

(73,3)

(73,4)

Calibrated ATWD Calibrated FADC

(73,5)

(73,6)

(73,7)

CascadeFilter Level2: Example of (rare) event (data)with large charge

NCh=32 Nstrings=6

Dom#

Dom#

Dom# 6 Dom# 7

Dom# 6 Dom# 7

String 73

String 39

Depth dependence!

String 73

String 39

Q [p.e.]

Q [p.e.]

<Q

> [p

.e.]

<Q

> [p

.e.]

Cascade Filter Level3+4: Total charge per Dom vs depthEvents with large charge got removed - agreement between data and MC

Large charge eventsLarge charge events

Energy Reconstruction: final cut (Level8)Energy Reconstruction: final cut (Level8) CscdLlh energy reconstruction settings: S. Lafebre && B. Fox (PSU)

NuENuE

Log(TrueEn) - Log(RecoEn)Log(TrueEn) - Log(RecoEn) vs log(TrueEn) :vs log(TrueEn) :

Log(RecoEn)Log(RecoEn)

Depth dependent cut on RecoEnergyDepth dependent cut on RecoEnergy

Bel

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:B

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Ab

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:A

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Below dust layer: Below dust layer: Log(RecoEn)Cut =4.8 Log(RecoEn)Cut =4.8 25 NuE events (240 days)25 NuE events (240 days)

Above dust layer: Above dust layer: Log(RecoEn)Cut=4.2 Log(RecoEn)Cut=4.2 18 NuE events (240 days)18 NuE events (240 days)

Log10(Energy) for TrueLeadingCascade (NuE) at Level7: Log10(Energy) for TrueLeadingCascade (NuE) at Level7:

Log(RecoEn)>4.8Log(RecoEn)>4.8

… … OR Depth dependent Energy correction?OR Depth dependent Energy correction?

Energy resolutions at L8 (NuE MC) for CscdLlhVertex

At Level2 the problem visible, but not as serve as at Level8At Level2 the problem visible, but not as serve as at Level8

Level8Level8 Level2 Level2 (for a comparison)(for a comparison)

COGZ>0COGZ>0

COGZ<0COGZ<0