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Observation of the Observation of the Crab Nebula with the Crab Nebula with the
MAGIC TelescopeMAGIC Telescope
M. López-MoyaM. López-MoyaUniv. Complutense de Madrid,Univ. Complutense de Madrid,
on behalf of the MAGIC Collaborationon behalf of the MAGIC Collaboration
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OutlineOutline
IntroductionIntroduction
AnalysisAnalysis
Data SetData Set
First ResultsFirst Results
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Crab Nebula: the standard Crab Nebula: the standard candle (I)candle (I)
Remnant of a supernova explosion, occurred in 1054.
Pulsar injecting relativistic electrons into the nebula.
Emission predominantly by non-thermal processes, covering a huge energy range (radio to TeV).
First TeV source (Whipple Telescope, 1989).
Very strong and stable at TeV → our standard candle
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Crab Nebula: the standard candle Crab Nebula: the standard candle (II)(II)
SSC model SSC model fits the fits the observed observed spectrum.spectrum.
Inverse Inverse Compton Compton peak peak expected expected below 100 below 100 GeV.GeV.
Inverse-Compton Emission
SynchrotronEmission
MAGIC should MAGIC should see the IC-peak.see the IC-peak.
577 pixels, 3.5 deg 577 pixels, 3.5 deg
FOV cameraFOV camera
Fast pulse sampling: 300MHzFast pulse sampling: 300MHz
Optical signal transportOptical signal transport
17 m diameter dish17 m diameter dish Active mirror controlActive mirror control
The The MAGICMAGIC Telescope Telescope
Located at 2220m at La Palma Located at 2220m at La Palma
(Canary islands) (Canary islands)
Threshold: Threshold: 30 GeV30 GeV
Characteristics:Characteristics:
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Imaging Cherenkov Technique Imaging Cherenkov Technique (I)(I)
-like-like hadron-likehadron-like -arc-arc
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Imaging Cherenkov Technique Imaging Cherenkov Technique (II)(II)
Alpha
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Background reduction (I)Background reduction (I) Down to Down to ~~150 GeV, the traditional techniques 150 GeV, the traditional techniques
based on based on simple image parameter cutssimple image parameter cuts, still , still work well.work well.
E>180 GeVE>180 GeV
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Background reduction (II)Background reduction (II) At lower energies the traditional At lower energies the traditional
techniques start to be not so effective. techniques start to be not so effective.
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Background reduction (III)Background reduction (III)
A new approach has been used for the A new approach has been used for the gamma/hadron separation: gamma/hadron separation:
Random ForestRandom Forest
Train in the parameters: Train in the parameters: SIZE, DISTANCE, LENGTH, SIZE, DISTANCE, LENGTH, WIDTH, CONC, ASYM WIDTH, CONC, ASYM (no ALPHA used).(no ALPHA used).
No a priori No a priori parameterization needed.parameterization needed.
For each shower we get For each shower we get its “hadronness”.its “hadronness”.
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Background reduction (IV)Background reduction (IV)
For each energy bin we cut in different For each energy bin we cut in different Hadronness and AlphaHadronness and Alpha
All EnergiesAll Energies E>200 GeVE>200 GeV
GammasGammas
HadronsHadrons
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Energy EstimationEnergy Estimation Basic principle:Basic principle: Energy Energy light content of the shower (SIZE). light content of the shower (SIZE).
We use a Taylor expansion on the more relevant image We use a Taylor expansion on the more relevant image parameters:parameters:
Coefficients obtained by minimizing:Coefficients obtained by minimizing:
Resolution ~30%Resolution ~30% Bias at very low energies, since very low size events are Bias at very low energies, since very low size events are
rejected (by trigger and analysis cuts).rejected (by trigger and analysis cuts).
),,,,( ZENITHWIDTHLENGTHDISTSIZEEE
estestMC EEEE /)(
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Energy EstimationEnergy Estimation
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Energy EstimationEnergy Estimation Basic principle:Basic principle: Energy Energy light content of the shower (SIZE). light content of the shower (SIZE).
We use a Taylor expansion on the more relevant image We use a Taylor expansion on the more relevant image parameters:parameters:
Coefficients obtained by minimizing:Coefficients obtained by minimizing:
Resolution ~30%Resolution ~30% Bias at very low energies, since very low size events are Bias at very low energies, since very low size events are
discarded (by trigger and analysis cuts).discarded (by trigger and analysis cuts).
),,,,( ZENITHWIDTHLENGTHDISTSIZEEE
estestMC EEEE /)(
Currently applying new methods, like Random Forest energy Currently applying new methods, like Random Forest energy estimation, giving similar results. estimation, giving similar results.
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Data SetData Set
datedate Zd. [Zd. [00]]Nº Nº
events events [·10[·1033]]
TTobsobs [min][min]
ONON 13,14,213,14,222
14-3014-30 12221222 110110
OFFOFF 18,2118,21 11-3011-30 885885 7070
First data set after full mirror First data set after full mirror installation: Sept. 2004installation: Sept. 2004
Background rate Background rate ~~200 Hz200 Hz
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Collection Area & Expected Collection Area & Expected RatesRates
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Alpha plots vs. EnergyAlpha plots vs. Energy
ON
OFF
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SpectrumSpectrum
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ConclusionsConclusions
MAGIC already operational and taking its MAGIC already operational and taking its first data since 2004.first data since 2004.
Crab Nebula spectrum measured by Crab Nebula spectrum measured by MAGIC consistent with previous MAGIC consistent with previous experiments, and compatible with SSC experiments, and compatible with SSC emission model.emission model.
First signals obtained well below 100 GeV First signals obtained well below 100 GeV with a Cherenkov telescope. with a Cherenkov telescope.
Analysis still can improve to push down Analysis still can improve to push down more the analysis threshold.more the analysis threshold.