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Time variable analysis. AWG videoconf – November 4 th 2010. A bit of history : 4 presentations during last collaboration meetings : - CERN ( fev 2010): description of the method - Clermont ( may 2010): + results with BBFit

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slide1

Time variable analysis

AWG videoconf – November 4th 2010

slide2

A bit of history: 4 presentationsduringlastcollaborationmeetings:

- CERN (fev 2010): description of themethod

- Clermont (may 2010): + resultswithBBFit

- Paris (sept 2010)+MANTS: + resultswithAAFit

Contents:

- Introduction

* Motivation

* Likelihoodmethod

- AnalysiswithBBFit and AAFit

* Data/MC comparison

* Performances of thealgorithm ( fixedsource)

* Candidatesourcessearch

* Systematicerrors

- Summary and perspectives

slide3

Introduction: motivation

More than 50% of sources are foundtobe variable…

→ Use this time informationdireclty in theanalysis:

* reduce effectivelythebackground

* improvethediscoverypotentialovera time integratedsearch.

→ Searchforsignalfromblazars AGN – candidatesourcesfor UHECR

(p-γor p-p  strongcorrelationbetweenγ-rayand neutrino fluxes)

  • γ-ray catalogues:
  • Fermi (>100 Mev - ~10 GeV)
  • IACT (>100 GeV)
slide4

Introduction: Likelihoodmethod

Method: unbinnedsearchusing a likelihood ratio (Garo’smethod)

Noise:

Signal:

Only up-goingmultilineevents (2008 data ~57 days)

Optimizationin ordertofindthemimimum neutrino flux tohave a 3 (5)sigma discovery

slide5

Unbinnedanalysis: 1) data

Time distribution of theupgoingmulti-line eventsreconstructedwithBBFit and selectwith tchi2<1.8

slide6

Unbinnedanalysis: 1) data

Time distribution of theupgoingmulti-line eventsreconstructedwithBBFit and selectwith tchi2<4

1st approx: flat distribution.

Next: use direcltythiskind of distributionwithveryloosecut as the time PDF forbackground

slide7

Unbinnedanalysis: 2) data/MC comparison

AAFit

BBFit

Reconstruction: AAFit v0r6 (+Antdst)

Reconstruction: BBFit v3r6

  • MC productions:
  • Add 2ns hit smearing
  • 12L 3pe + 10pe periods
  • Neutrino+antineutrino: Bartol flux
  • Muons: corsika + bugaevnormalisation + scale *2
  • MC productions:
  • Add 2ns hit smearing + 0.5ns interline (cfNickef’s PS) + noiseextractedfromsummaryfilefromall 2008 L12 data.
  • Neutrino+antineutrino: Bartol flux
  • Muons: mupage (~13.9days)
  • Data: interline offset (cfNickef’s PS)

Legend: data: blackdots

MC un+anu: blue line

MC muons: red line

MC all: green line

slide8

Unbinnedanalysis: 2) data/MC comparison

AAFit

BBFit

Upgoingeventswith error estimateβ<1º

Upgoingeventswithnline>1 && nhit>5

slide9

Unbinnedanalysis: 2) data/MC comparison

AAFit

BBFit

Alleventswithβ<1º && Λ>-5.4

Alleventswithnline>1 && nhit>5 && tchi2<1.5

slide10

Unbinnedanalysis: 2) data/MC comparison

AAFit

BBFit

Upgoingeventswith error estimateβ<1º && Λ>-5.4

Upgoingeventswithnline>1 && nhit>5 && tchi2<1.5

slide11

Unbinnedanalysis: 2) data: number of events

AAFit

BBFit

Upgoingeventswith error estimateβ<1º

Upgoingeventswithnline>1 && nhit>5

slide12

Unbinnedanalysis: 3) performances

AAFit

BBFit

Upgoingeventswithnline>1 && nhit>5 && tchi2<1.2, 1.4, 1.6…, 3.0

Upgoingeventswithβ<1º && Λ>-4.8, -4.9, -5.0,…-5.8

slide13

Unbinnedanalysis: 3) performances

AAFit

BBFit

Upgoingeventswithnline>1 && nhit>5 && tchi2<1.2, 1.4, 1.6…, 3.0 && tcosth>0.17

Upgoingeventswithβ<1º && Λ>-4.8, -4.9, -5.0,…-5.8

(Integration E-2spectrumfrom 10GeV-10PeV)

slide14

Unbinnedanalysis: 3) performances

Unbinnedanalysis: comparisonAAFit / BBFit

AAFit

BBFit

Upgoingeventswithnline>1 && nhit>5 && tchi2<1.5, 1.8, 2.0

Upgoingeventswithβ<1º && Λ>-5.0, -5.4, -5.8

slide15

Unbinnedanalysis: 3) performances

δ=-40º

AAFit

BBFit

Upgoingeventswithnline>1 && nhit>5 && tchi2<1.2, 1.4, 1.6…, 3.0

Upgoingeventswithβ<1º && Λ>-4.8, -4.9, -5.0,…-5.8

slide16

UnbinnedanalysiswithAAFit and BBFit:

  • Twomainsteps:
  • 1) Determination of the performances of theunbinnedmethodalgorithm:
  • Generation of theevents in one single sourcewithone single flare [squareshape] with a variable widthfrom 0.1day to 84days and withoutusingthetiminginformation.
  • 2) Candidatesourcessearch:
  •  Use the full time PDF of thesourceextractedfromthe gamma ray light curve.
slide17

UnbinnedanalysiswithAAFit: fixedsearch

Yellow: bkg

Red: bkg+1 event

Green: bkg+3 events

Blue: bkg+5 events

Pink: bkg+7 events

Light blue:bkg+9 events

slide18

UnbinnedanalysiswithAAFit: fixedsearch

Zeroproblem:

 Difficultcomputation of thesensitivityespeciallyforvery short flare

comes fromthefactthattheprobabilitytohaveexactly 0 eventsaroundonesource at lessthanfewdegresincreases (lessproblematicforBBFit)

 Stability of thefit in ordertofindthecutfor 5s

  • Solutions:
  • Extendtheradius of thesimulation of thebackground: 3º->20º
  • Add a smallrandomnumbertothelikelihood ratio: Uniform(10-5)
  • Increasethestatisticforthe PE generation105 -> 107(especiallyforveryrestrictive lambda value)
slide20

UnbinnedanalysiswithAAFit: fixedsearch

Stability of thefit 35σ

1day

84 days

3 days

No timing

0.1 day

No timing

slide21

UnbinnedanalysiswithAAFit: fixedsearch

Number of eventsneededfor a 3σdiscovery

FordifferentcutonΛvalue: >-4.8, -4.9, -5.0…-5.8

ConversionNevent Flux withthevisibility, effectivearea and live time

slide23

UnbinnedanalysiswithAAFit: fixedsearch

No timing

25 days

10 days

1 day

slide26

UnbinnedanalysiswithAAFit: candidatesource

Fermi Sources: July – December 2008

→ Selection of Blazars

→ Flux (>300MeV) > 20 10-8 photons.cm-2.s-1 (highstate)

→ Variabilityσ2NXS > 0.15 (Abdo et al, ……..)

Selection

slide27

UnbinnedanalysiswithAAFit: candidatesource

Fermi gamma-ray light curve for 3C454.3

Time PDF

(beforenormalisation)

(Flare’sdetermination: cftalk at Paris)

slide29

UnbinnedanalysiswithAAFit:

Expectedresultsforthesensitivity (90% CL) and forthe 3(5) σdiscoverypotential (50% prob)

Flux: GeV.m-2.s-1

slide30

UnbinnedanalysiswithAAFit:

Expectedresultsforthesensitivity (90% CL) and forthe 3(5) σdiscoverypotential (50% prob)

slide31

UnbinnedanalysiswithAAFit:

  • 2 sources of systematicerrors:
  • Angular resolution: makeworsethe angular resolutionby a factor 15% appliedwitha gaussiandistribution (cfAartpointsource )
    • Keepthesame PDF butchangeonlythe PSF forthegeneration
    • Efficiency: makeworsetheefficiencyby a factor 30%
    • changethenumber of eventsinjected in thesample (gauss(1,0.3))
    • - Extrapolation 3->5σ ?
    • - Otherssources: absolutepointing, …
slide32

UnbinnedanalysiswithAAFit:

Expectedresultsforthesensitivity (90% CL) and forthe 3(5) σdiscoverypotential (50% prob) includingthesystematicerrors

Averageeffect:

Sensititivty: ~1.10

Discovery: ~1.20

slide34

UnbinnedanalysiswithBBFit: fixedsource

Declination : -40º

No timing

10days

0.1day

1day

slide38

UnbinnedanalysiswithBBFit: candidatesource

Expectedresultsforthesensitivity (90% CL) and forthe 3(5) σdiscoverypotential (50% prob)

Flux: GeV.m-2.s-1

1.8: 451 bkgevents 2.4: 2748 bkgevents

2.0: 791 bkgevents 3.0: 8702 bkgevents

slide39

UnbinnedanalysiswithBBFit: candidatesource

Expectedresultsforthesensitivity (90% CL) and forthe 3(5) σdiscoverypotential (50% prob)

slide40

UnbinnedanalysiswithBBFit: candidatesource

Expectedresultsforthesensitivity (90% CL) and forthe 3(5) σdiscoverypotential (50% prob) includingthesystematicerrors.

Samesource of systematicerrorsthantheonesusedwithAAFit:

- Ang Res: +gauss(1,0.15)

- Efficiency: +gauss(1,0.3) ontheinjectednumber of signalevents

Averageeffect:

Sensititivty: ~1.20

Discovery: ~1.15

slide43

Summary and perspectives:

Unbinnedanalysis of the Fermi sources in 2008 (~57 days) is (almost) done. Internalclosetobefinished

Perspectives:

1) Use the time distribution of the data in ordertosimulatebackgroundeventsand tobuildthe time PDF.

Example: alleventsreconstructedwiththe on-line BBFitwith at least 2 lines and a fitquality, tchi2<4.0

slide44

Summary and perspectives:

Time variable analysisseemstoworkedusingBBFitorAAFitwiththe12L data in 2008

Perspectives:

2) Extendtheanalysisto 2009-10 data

Missing:

Data: BBFit-> OK

Data: interline offset ?

MC: on-going, help ?

Source 3C454.3 gamma-ray light curve fromAug 2008 toSept 2010

slide45

Summary and perspectives:

Time variable analysisseemstoworkedusingBBFitorAAFitwiththe12L data in 2008

Perspectives:

2) Extendtheanalysisto 2009-10 data

Missing:

Data: BBFit-> OK

Data: interline offset ?

MC: on-going, help ?

Time distribution of the data for 2008-09-10 reconstructedwithBBFit (tcosth>0&&tchi2<1.8&&nline>1&&nhit>5)