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Using direct photons to calibrate/monitor L1Calo

Using direct photons to calibrate/monitor L1Calo. Hardeep Bansil University of Birmingham L1Calo Joint Meeting, Heidelberg January 11 – 13, 2010. Talk Outline. Direct Photons Motivation Analysis Results so far Next steps Data so far Summary. Direct Photons.

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Using direct photons to calibrate/monitor L1Calo

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  1. Using direct photons to calibrate/monitor L1Calo Hardeep Bansil University of Birmingham L1Calo Joint Meeting, Heidelberg January 11 – 13, 2010

  2. Talk Outline • Direct Photons • Motivation • Analysis • Results so far • Next steps • Data so far • Summary

  3. Direct Photons • ‘Direct’ or ‘prompt’ photons originating directly from hard pp interaction • Leading order processes • Compton (qg) • Annihilation (qq) Francesca Bucci, 10/2008, Direct Photons at ATLAS

  4. Direct Photons • Have a γj final state • Background from ‘fake’ photons created in the jet • Long term strategy – Select events that were triggered by jet and get efficiency for γ (and vice versa) Direct photon event signature seen in ATLANTIS Event Display, Mark Stockton, Production of Direct Photons at ATLAS, 6-8/4/2009

  5. Direct Photons • Jet and photon in event • Higher cross section than Z→ee (approx 2 orders of magnitude) • γ complementary to e but still isolated Carminati, 28/8/2009

  6. Motivation • Using direct photons for: • Efficiency determination of electromagnetic and jet triggers • Monitoring and calibration of L1Calo with physics objects

  7. Analysis • Using Athena version 15.5.1 • Using Analysis package from John Morris • with some modifications! • Using MC Direct Photon data files • PYTHIA, √s = 10 TeV, pT > 150 GeV • Get reconstructed offline photons in each event • Select the photon with highest ET • Compare with EmTau RoIs

  8. Results so far • Distributions for highest ET offline reconstructed photons • MC pT cut at 150 GeV – v. high • Want to look at lower energies

  9. Results so far • Distributions for all EmTau RoIs • Not too different to offline photons

  10. Results so far • Resolution in η, Δη = ηOfflinePhoton – ηEmTauRoI All Photons Direct Photons (> 50 GeV)

  11. Results so far • Resolution in φ, Δφ = φOfflinePhoton – φEmTauRoI All Photons Direct Photons (> 50 GeV)

  12. Results so far • Calculate Δr = √((Δη)2+(Δφ)2) using offline photon and EmTau RoI • Good photons have Δr < 0.4, ignore the rest (less than 5%)

  13. Results so far • Look at ‘triggered’ EmTau RoIs again (Δr < 0.4) • ET distribution matches offline highest ET photon better

  14. Results so far • EmTau RoI v Offline Photon Energy • EmTau RoI energies seem higher than those for photons Direct photons Fake photons

  15. Results so far • Resolution in ET = (ET,Phot- ET,RoI)/ET,Phot All Photons Direct Photons (> 50 GeV)

  16. Results so far • Trigger Isolation Energy – observe ET behaviour when isolation is / is not set for EmTau RoI thresholds • All γ • Highest ETγ Bit 05 – Isolation < 5 GeV, ET > 20 GeV Bit 01 – No Isolation, ET > 7 GeV

  17. Results so far • Efficiency in ET for EmTau RoIs = RoI Δr < 0.4 & EM/TAU Threshold passed RoI Δr < 0.4 Big loss at low ET Bit 06 – Isolation < 5 GeV, ET > 24 GeV Bit 02 – No Isolation, ET > 14 GeV

  18. Results so far • Efficiency in ET – this time for offline photons • Not as clean as for RoIs Bit 06 – Isolation < 5 GeV, ET > 24 GeV Bit 02 – No Isolation, ET > 14 GeV

  19. Next steps • Check code with other simulated direct photon datasets • Direct photons generated with lower ET threshold • Comparisons of reconstructed offline photons with truth level • Looking at real data!

  20. Data so far • Run 142193, 900 GeV, 152000 events in dataset) – 101 medium offline electrons found • Still too low statistics to do proper analysis Juergen Thomas, 20/12/2009

  21. Summary • Direct photons • Monitor / calibrate • Good results with current MC data • Look at more data

  22. Thank you for listeningAny questions / comments / suggestions? Thanks to Paul Newman, JurajBracinik, Miriam Watson and Juergen Thomas for their help

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