Analysis chain for MAGIC Telescope data Daniel Mazin and Nadia Tonello Max-Planck-Institut für...

Analysis chain for MAGIC Telescope

data

Daniel Mazin and Nadia Tonello Max-Planck-Institut für Physik München

D.Mazin, N.TonelloMPI for Physics, Munich

ISCRA 14th Course Erice, 2nd-13th July 2004



Tech

niq

ue

~ 10 km

~ 1o

Ch

eren

kov

ligh

t

~ 120 m

Particleshower

AtmosphereCherenkov light Image of particle shower in telescope camera:

Imaging AirCherenkov Telescope

Calib

rati

on

MAGIC Camera



Calibration runs: same number of photons in all PMs

Calibration methods: Ffactor method (relative calibration)Muons (absolute calibration)Blind-pixel method …to be installed

Charg

e

extr

act

ion



Extract signal from ADC data:

• signal digitized every 3.3 ns

• pedestal subtraction

• sum N-ADC slices

• N=large: collect charge in tails

• N=small: reduce

NightSkyBackground contribution

• typical value: N=4

Pulse shape after pedestal subtraction

Calib

rati

on

MAGIC Camera



Calibration runs: Output of PMs not uniform

After calibration: All PMs show the same photon density

Relative pixel to pixel calibration

Q Mean charge for pixel

from a calibration run 2

Q variance from the charge

distributions of the pixel

F2 correction for intrinsic noise

of the photomultiplierCalib

rati

on



Mean number of photoelectrons

Nphel = (Q2/ 2Q) F2

where F2= 1.335 (measured)

absolute calibration in number of photoelectrons

Image c

leanin

g



Calibrated charge Arrival time

Signal/Noise Shower image

Hill

as

Para

mete

rs



gamma shower hadron shower (background)

muon shower

Shower reconstruction and background rejection based on image shape analysis

Hillas parameters:LENGTH, WIDTH, DISTANCE,SIZE, ALPHA, …

-h

ad

ron

sep

ara

tion



MC-Black: dataMC-hadrons

MC-Black: dataMC-hadrons

PRELIMINARY

-hadron separation by using cuts in:

• LENGTH, WIDTH,

DISTANCE, etc

Since all these parameters are not independent, we use

Dynamical cuts

LENGTH

WIDTH

Remark: cuts are optimized using ON and OFF data.

MC data are not used for optimization due to ongoing tuning of MC

-h

ad

ron

sep

ara

tion



SuperCutshadrons

gammas

SIZE

WID

TH

Current analysis

-h

ad

ron

sep

ara

tion



Mean Scaled HillasFor each SIZE bin Mean value of LENGTH is calculated

(red curve). Black curves – optimized cuts on LENGTH.

Alp

ha p

lot



Sourc

e P

osi

tion



First step: pointing and tracking precision• Star guider (online correction, being commissioned)• Use anode currents to determine star positions (offline)

For determination of the source dependant parameters:SOURCE POSITION is needed

Preliminary results by using anode currents:

• Position with a statistical error ~0.01

• possible to detect stars until 8th magnitude in the inner pixels

• updating every 10 sec

Second step: determine source position (known coordinates)

Triangulation Crab Nebula

Mrk 421H1426+428

3C279

Fals

e S

ou

rce M

eth

od



If the source position unknown:

1. For each position in FoV the source dependant parameters are calculated

2. The same for the OFF data

3. For all positions in FoV the alpha plot is produced and Nexcess / significance are calculated

~5min of Mrk421 data

~5min of Mrk421 data

OU

TLO

OK



Other analysis techniques:

• Further optimization of gamma-hadron separation using Hillas parameters:

• Random Forest (is used)

• Neural Net (ready to be used)

• Fit the complete camera event information:

• Model Analysis (being development)

• Lightcurve (gamma-flux as a function of time)

• Energy spectrum

Further analysis steps:

OU

TLO

OK



NEXT TALK:

MAGIC first results

presented by Ester Aliu

Analysis chain for MAGIC Telescope data Daniel Mazin and Nadia Tonello Max-Planck-Institut für...

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