1. Update on Conversions SCIPP ATLAS Meeting February 17 2009 Bruce Schumm, UCSC/SCIPP

2. Step I: Reconstruction Have migrated from 14.2.20 with two patches to standard 14.5.0 (confirmed with Thomas Koffas that this is current best) Reconstruct 50 events of GMSB2 for now – will need to increase by x10 or more soon. Large GMSB1 samples reconstructed in 14.2.20.3, which (I’m fairly sure) is not appropriate for conversions.

3. Step II: Find the Conversions Am now using the conversion in the standard EGamma list rather than those in the Conversion container  much more filtered. Number of reconstructed conversions down by factor of 5-10. Step III: Truth Matching Have worked through “track” truth matching for conversions (thanks to code snippet from Thomas). Truth match only if an electron or positron from a photon conversion (1-track conversions) or one electron and one positron from a photon conversion (2-track conversions). 52/85 ~ 60% are truth matched, but…

4. Step III: Rconstruction Comparison for Truth- Matched Conversions (compare true photons with EGamma reconstructed photon ) Define momentum difference P as P = (p reco – p truth )/p truth Let R be the three-dimensional angle between the true and reconstructed photon. Let O between the difference in the true and reconstructed radial position of the conversion.

5. 3D Angular Separation Closest True Conversion Truth-Matched Conversion GMSB2 Low Statistics

6. Momentum Difference Closest True Conversion Truth-Matched Conversion GMSB2 Low Statistics

7. Difference in Radius of Origin Truth-Matched Conversion Next, look with higher stats (150 events  150 events), and separate between 1- and 2-track conversions GMSB2 Low Statistics

8. GMSB2 3D Angular Separation GMSB2 Higher Statistics All Truth- matched Conversions Two-track Conversions One-track Conversions

9. GMSB2 Momentum Difference GMSB2 Higher Statistics All Truth- matched Conversions Two-track Conversions One-track Conversions

10. And try GMSB1… 3D Angular Separation GMSB2 (300 Events) All Truth- matched Conversions Two-track Conversions One-track Conversions

11. GMSB1 Momentum Difference GMSB1 (300 Events) All Truth- matched Conversions Two-track Conversions One-track Conversions

12. Some ideas for what to do next… *) Just look at GMSB conversions (almost all set up to do that *) Look at the individual truth-matched electron/positron tracks *) Look at truth-matched pions to see if bremsstrahlung is causing trouble…