DATA ANALYSIS: EXTRACTING SCIENCE FROM MAGIC

Transcription

1 DATA ANALYSIS: EXTRACTING SCIENCE FROM MAGIC Uta Menzel YSW Ringberg 2015,

2 OUTLINE MAGIC telescopes Imaging Air Cherenkov Technique (IACT) Telescope hardware Standard analysis Signal extraction Hillas parametrization Determination of physical parameters Final products My work - Template analysis Uta Menzel YSW Ringberg 2015, / 27

3 THE ATMOSPHERE Uta Menzel YSW Ringberg 2015, / 27

4 EXTENSIVE AIR SHOWERS Electromagnetic shower e + Primary e + e - e - e + e - e + e - e - e + particle cascade with pair production bremsstrahlung charged particles, faster than speed of light in air Cherenkov radiation Uta Menzel YSW Ringberg 2015, / 27

5 Data Analysis: Extracting science from MAGIC I MAGING A IR C HERENKOV T ECHNIQUE I image with elliptic shape I stereo for better reconstruction I background from cosmic rays, ~factor 1000 Christian Fruck Uta Menzel YSW Ringberg 2015, / 27

6 Data Analysis: Extracting science from MAGIC Main Imaging Air Cherenkov Telescopes Uta Menzel YSW Ringberg 2015, / 27

7 Data Analysis: Extracting science from MAGIC The MAGIC telescopes I 2200 m above sea level I parabolic dish: 17 m diameter I 2 telescopes, 85 m apart I focal length: 17 m I light structure fast repositioning I 1 m2 and 0.25 m2 mirrors Uta Menzel YSW Ringberg 2015, / 27

8 Data Analysis: Extracting science from MAGIC C AMERA Uta Menzel I PMTs (photo multiplier tubes) as photon detectors I 1039 pixels per camera I ~1 m diameter I 3.5 field of view YSW Ringberg 2015, / 27

9 ELECTRONICS trigger L0: minimum signal in single pixel L1: signal in neighbouring pixels L3: trigger in both telescopes readout: DRS4 chip up to 2 GSamples/s 1024 capacitors saved to disk: 60 time slices with charge (30 ns in total) for each pixel Uta Menzel YSW Ringberg 2015, / 27

10 DATA ANALYSIS Uta Menzel YSW Ringberg 2015, / 27

11 SIGNAL EXTRACTION pedestal subtraction search for signal (sliding window) for each pixel: number of photo electrons arrival time Uta Menzel YSW Ringberg 2015, / 27

12 IMAGE CLEANING Two-level image cleaning core pixel: number of photons above threshold 1 boundary pixel: neighbour of core pixel, number of photons above threshold 2 <threshold 1 include time contraints for core and boundary calibrated image core and boundary cleaned image Uta Menzel YSW Ringberg 2015, / 27

13 PARAMETRIZATION Mono Hillas Parameters number of photons length Source position distance length α center of gravity width width distance to source α time parameters... Christian Fruck Uta Menzel YSW Ringberg 2015, / 27

14 PARAMETRIZATION Stereo Hillas Parameters Reconstructed origin theta disp 2 Source position length 2 distance 1 distance 2 disp 1 α 2 length 1 center of gravity 2 α 1 width 2 number of photons length width distance to source α time parameters... Camera 1 Camera 2 center of gravity 1 width 1 Uta Menzel YSW Christian Ringberg Fruck 2015, / 27

15 RECONSTRUCTION based on Monte Carlo simulations atmosphere as part of the detector simulate the telescope response analyze like data parameters to reconstruct: energy of the primary particle: look-up table direction the of primary particle: stereo disp method hadronness: Random Forest Uta Menzel YSW Ringberg 2015, / 27

16 DIRECTION RECONSTRUCTION geometrical stereo reconstruction mono DISP reconstruction with Random Forest stereo DISP combine DISP of both telescopes to get direction Uta Menzel YSW Ringberg 2015, / 27

17 GAMMA-HADRON SEPARATION Electromagnetic shower Primary Hadron shower Cosmic Ray (p,, Fe...) e + e - Atmospheric Nucleus e + e - e + e - e + e - e - e + EM Shower EM Shower Nucleons, K, etc. Atmospheric Nucleus Nucleons, K, etc. e - + e - e + e+ EM Shower Uta Menzel YSW Ringberg 2015, / 27

18 GAMMA-HADRON SEPARATION Gamma Hadron Uta Menzel YSW Ringberg 2015, / 27

19 GAMMA-HADRON SEPARATION Decision tree Random Forest = many decision trees build with MC-gammas and real background determine hadronness of each event Uta Menzel YSW Ringberg 2015, / 27

20 SIGNAL DETECTION θ 2 -plot Skymap angular resolution ~0.1 background estimated from camera region without source Uta Menzel YSW Ringberg 2015, / 27

21 EFFECTIVE COLLECTION AREA A eff [m 2 ] determined from MCs (same analysis as data) A eff = N survived N simulated A simulated Uta Menzel YSW Ringberg 2015, / 27

22 MIGRATION MATRIX relation between simulated and reconstructed energy energy spectrum needs unfolding energy resolution ~15% Uta Menzel YSW Ringberg 2015, / 27

23 SPECTRUM Uta Menzel YSW Ringberg 2015, / 27

24 ALTERNATIVE ANALYSIS METHOD Uta Menzel YSW Ringberg 2015, / 27

25 Current analysis Calibrated data Template analysis Hillas method compare to template images Calibrated data Uta Menzel YSW Ringberg 2015, / 27

26 TEMPLATE DATABASE parameters that change the image: energy azimuth zenith angle impact parameter impact angle (ϕ) first interaction height 6D-database + pointing: (x cam, y cam ) source Uta Menzel YSW Ringberg 2015, / 27

27 TEMPLATE ANALYSIS PROCEDURE E, source pos. direction,... Hillas template database compare data with template new starting point data - Energy - Source position - Fit quality? comparison: likelihood function maximization of the likelihood Uta Menzel YSW Ringberg 2015, / 27

28 CONCLUSION IACT: new window to gamma-ray astronomy MAGIC: largest IACT stereo system standard analysis: based on image parameters possible improvement: template analysis better angular resolution better energy resolution higher sensitivity Uta Menzel YSW Ringberg 2015, / 27