1. First Look at Conversions for Non-Pointing Photons US ATLAS Egamma Meeting March 12 2009 Bruce Schumm, UCSC/SCIPP

2. Motivation Gauge-mediated supersymmetry breaking (GMSB) tends to have a Gravitino (G) LSP, with a decay- chain ending with  0  G +  Since gravity is weakly coupled, the neutralino (  0 ) can be metastable, leading to hard photons that don’t point back to the collision point. Studies (Helen Hayward, Mark Terwort) suggest that CAL can be used to detect these and constrain decay length, masses.

3. IDEA: Perhaps conversions can be used to Increase signal efficiency Increase pointing accuracy Provide direct constraint on decay length Mauro Donega, UPenn Reconstructed radius of material-induced conversions

4. Former Major Issue: GMSB reconstruction Official GMSB samples reconstructed in 14.2.?; not fully adequate for conversions.  Re-reconstruct in 14.5.0. Have not yet figured out how to handle large (~10000 event) samples. [Advice/discussion?]. Thus: GMSB1 (pointing):637 events GMSB2 (non-pointing):952 events Statistics are marginal… This just in: GMSB samples in 14.2.25.6, which is OK!

5. Goal: Explore efficiency and accuracy of reconstruction for GMSB photon conversions Efficiency denominator Conversions of photons with a direct  0 parent, and with p t > 10 GeV/c and |  | < 1.5 Efficiency numerator Include both one- and two-track conversions that truth- match to a “efficiency denominator” conversions One-track conversion: Track must truth-match to the electron or positron from the denominator conversion Two-track conversion: Tracks must truth-match to the electron and positron from the denominator conversion

6. Momentum Distribution for Pointing Sample Two-track Conversions GMSB PRIMARY CUT NOT GMSB GMSB SECONDARY GMSB “DENOM- INATOR”

7. Angular distribution of GMSB Conversions eta GMSB “Denominator”

8. Radial distribution of GMSB Conversions GMSB “Denominator”

9. Efficiency and accuracy of Reconstruction of “Denominator” GMSB Conversions NOTE: Eff. based on STRICT truth-matching GMSB efficiency vs. conversion radius

10. Efficiency vs. angle and p t eta ptpt

11. Accuracy of Good GMSB momentum reconstruction 1-track conversions 2-track conversions Momentum measurement of 1-track conversions more accurate than 2-track conversions (?)

12. Can we make use of 1-track conversions for decay-length studies? 410mm Accuracy of Good GMSB conversion radius reconstruction 1-track conversions 2-track conversions