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The islands method in the image analysis of atmospheric Cherenkov Telescopes data

The islands method in the image analysis of atmospheric Cherenkov Telescopes data. Nadia Tonello and Keiichi Mase Max-Planck-Institut für Physik München. DPG Spring Meeting 2004 Mainz, March 29 th -April 1 st. Nadia Tonello MPI for Physics, Munich.

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The islands method in the image analysis of atmospheric Cherenkov Telescopes data

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  1. The islands method in the image analysis of atmospheric Cherenkov Telescopes data Nadia Tonello and Keiichi Mase Max-Planck-Institut für Physik München DPG Spring Meeting 2004 Mainz, March 29th -April 1st Nadia Tonello MPI for Physics, Munich

  2. Previous generation of Cherenkov Telescopes (energy range TeV) successfully adopted Standard Image Cleaning and Hillas Parameters to analyze data. • New generation of Cherenkov Telescopes can record images produced by atmospheric showers initiated by (100-100) GeV particles. • Sometimes, the images are fragmented and the standard image cleaning miscalculates the image parameters. • An Island is defined as a group of pixels connected with each other above a certain threshold (noise RMS units = sigma). • The image parameters are calculated for each island and used for the g/h separation. • Using islands parametersmore detailed informations can be potentially extracted. DPG Spring Meeting 2004 Mainz, March 29th -April 1st Nadia Tonello MPI for Physics, Munich

  3. Gamma shower ( narrow, points to source ) h (m) m 100 GeV proton h(m) CT1 Camera Alpha Width Length Proton shower ( wide, points anywhere ) Length Alpha Width DPG Spring Meeting 2004 Mainz, March 29th -April 1st Nadia Tonello MPI for Physics, Munich

  4. Distributions of the Number of Islands HEGRA CT1 Real data (hadrons) MC gammas 9.5 0.4 10.8 2.5 0.3 0.2 25.0 4.3 0.2 0.1 0.1 0.1 22.6 9.5 3.0 1.0 0.5 0.2 0.2 39.4 27.1 6.2 1.7 0.5 0.2 0.2 37.7 33.1 20.5 11.3 7.3 5.5 3.8 28.9 54.9 76.2 87.5 92.2 94.3 96.0 26.1 68.2 93.6 98.2 99.499.7 99.8 Energy threshold : 750 GeV DPG Spring Meeting 2004 Mainz, March 29th -April 1st Nadia Tonello MPI for Physics, Munich

  5. Standard Analysis HEGRA CT1 After Supercuts : 97% of the survived events have only 1 main island 9.5 0.4 10.8 2.5 0.3 0.2 25.0 4.3 0.2 0.1 0.1 0.1 22.6 9.5 3.0 1.0 0.5 0.2 0.2 39.4 27.1 6.2 1.7 0.5 0.2 0.2 37.7 33.1 20.5 11.3 7.3 5.5 3.8 28.9 54.9 76.2 87.5 92.2 94.3 96.0 26.1 68.2 93.6 98.2 99.499.7 99.8 DPG Spring Meeting 2004 Mainz, March 29th -April 1st Nadia Tonello MPI for Physics, Munich

  6. Distributions of the Number of Islands MAGIC Number of pixels >2 Energy threshold: 30 GeV Cleaning level: 2.5 sigma Gammas Hadrons DPG Spring Meeting 2004 Mainz, March 29th -April 1st Nadia Tonello MPI for Physics, Munich

  7. Example MC Gamma Energy : 35.7 GeV I.P. : 112 m MAGIC Camera Standard I.C. Alpha : -17.4° Length : 143 mm Width : 18.7 mm Size : 494 photons Islands Analysis Island1 # pixels : 9 Alpha : -3.29° Length : 42.6 mm Width : 18.1 mm Size : 434 photons Island2 # pixels : 2 Alpha : 18.8° Length : -1 mm Width : -1 mm Size : 60 photons Recon. Alpha : -3.29° DPG Spring Meeting 2004 Mainz, March 29th -April 1st Nadia Tonello MPI for Physics, Munich

  8. The Distribution of Alpha Standard I.C. Continent (Islands Analysis) RMS = 22.5 RMS = 26.0 Size > 300 ADC Number of pixels >2 Reconstructed (Islands Analysis) Islands analysis The alpha distribution is slightly narrower Better reconstruction power. RMS = 22.9 DPG Spring Meeting 2004 Mainz, March 29th -April 1st Nadia Tonello MPI for Physics, Munich

  9. The Distribution of Width Standard I.C. Continent (Islands Analysis) gamma gamma hadron hadron Size > 300 ADC DPG Spring Meeting 2004 Mainz, March 29th -April 1st Nadia Tonello MPI for Physics, Munich

  10. The Distribution of Length Standard I.C. Continent (Islands Analysis) Gammas Gammas Hadrons Hadrons Size > 300 ADC The islands information can be used as additional information. DPG Spring Meeting 2004 Mainz, March 29th -April 1st Nadia Tonello MPI for Physics, Munich

  11. G/h Separation • Input parameters Standard Analysis • Size • Width • Length • Dist • Conc2 • Sgn(M3Long) • Alpha Islands Analysis • Length of biggest island • Width of biggest island 16% improvement for Size 600-1000 ADC DPG Spring Meeting 2004 Mainz, March 29th -April 1st Nadia Tonello MPI for Physics, Munich

  12. Summary • At TeV energies the shower images are compact and the standard analysis is working fine. • Al lower energies, the standard image cleaning miscalculates the Hillas parameters due to the fragmentation of the shower images. • The different parts are called ISLANDS. • Islands analysis is hardly affected by NSB. That's why the islands parameters are calculated correctly. More informations can be potentially extracted. Island analysis is promising to analyze low energy showers DPG Spring Meeting 2004 Mainz, March 29th -April 1st Nadia Tonello MPI for Physics, Munich

  13. Outlook Systematic study on different cleaning levels potential rejection power of different islands parameters DPG Spring Meeting 2004 Mainz, March 29th -April 1st Nadia Tonello MPI for Physics, Munich

  14. Example 4 Standard I.C. Islands Analysis Gamma (#13) Energy : 61.9 GeV I.P. : 62.1 m # islands : 4 Island1 # pixels : 9 Alpha : -4.64° Length : 31.4 mm Width : 21.5 mm Size : 300 photons Island2 # pixels : 7 Alpha : -4.04° Length : 29.8 mm Width : 14.7 mm Size : 371 photons Island3 # pixels : 2 Alpha : 0° Length : -1 mm Width : -1 mm Size : 63 photons Alpha : 6.97° Length : 71.7 mm Width : 69.4 mm Size : 707 photons DPG Spring Meeting 2004 Mainz, March 29th -April 1st Recon. Alpha : -2.67° Nadia Tonello MPI for Physics, Munich

  15. Example 2 Standard I.C. Islands Analysis Gamma (#19) Energy : 50.6 GeV I.P. : 108 m # islands : 3 Island1 # pixels : 9 Alpha : -2.4° Length : 27.0 mm Width : 13.4 mm Size : 954 photons Island2 # pixels : 2 Alpha : -29.0° Length : -1 mm Width : -1 mm Size : 51 photons Island3 # pixels : 2 Alpha : 0° Length : -1 mm Width : -1 mm Size : 54 photons Alpha : -2.4° Length : 27.0 mm Width : 13.4 mm Size : 954 photons Recon. Alpha : -2.4° DPG Spring Meeting 2004 Mainz, March 29th -April 1st Nadia Tonello MPI for Physics, Munich

  16. Example 3 Standard I.C. Islands Analysis Gamma (#23) Energy : 19.3 GeV I.P. : 88.3 m # islands : 3 Island1 # pixels : 4 Alpha : -34.2° Length : 19.6 mm Width : 9.6 mm Size : 155 photons Island2 # pixels : 3 Alpha : 31.4° Length : 13.0 mm Width : 10.6 mm Size : 135 photons Island3 # pixels : 3 Alpha : 28.1° Length : 12.5 mm Width : 12.0 mm Size : 83 photons Alpha : -1.03° Length : 44.4 mm Width : 12.6 mm Size : 290 photons Recon. Alpha : -4.02° DPG Spring Meeting 2004 Mainz, March 29th -April 1st Nadia Tonello MPI for Physics, Munich

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