Further Update on Conversions

ATLAS Informal Non-Pointing Photon Meeting

February 25 2009

Bruce Schumm, UCSC/SCIPP

Reminder: Reconstruction

Working with 627 GMSB1 events reconstructed with 14.5.0 Reminder: 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).

~ 60% are truth matched

Reconstruction Comparison for Truth-Matched Conversions (compare true photons with EGamma photon reconstructed from conversions)

Define scaled momentum difference P as

(preco – ptruth)/ptruth

Scaled momentum difference for truth-matched conversions

Separate 1- and 2-track conversions

P-difference for 1-track

Conversions

P-difference for 2-track

Conversions

What could be causing this smearing? Am I truth-matching correctly?

Look at the scaled momentum difference for the individual conversion electrons, and also for unassociated pions…

Indivudual Track Comparisons

Electron momentum difference

Pion momentum difference

Truth-matching correct?

Electron reconstruction compromised by bremsstrahlung (brem recovery?)

Cataloging True Conversions

In preparation for studying reconstruction efficiency, separate conversions into those from GMSB photons and those not from GMSB photons.

Further discriminate for GMSB-related conversions:

“Secondary”: arises from bremsstrahlung of a GMSB-conversion electron

“Good”: conversion of a direct GMSB decay photon with pt > 10 and || < 1.5

“Bad”: direct GMSB decay photon that is not “Good”

Categorized Conversion Momentum Distributions

Two-track Conversions

GMSB “BAD”

NOT GMSB

GMSB SECONDARY

GMSB “GOOD”

Angular distribution of GMSB Conversions

cos (sorry…)

GMSB “Good”

Radial distribution of GMSB Conversions

GMSB “Good”

Latest work (yesterday): Efficiency and accuracy of GMSB Good

NOTE: Eff. based on STRICT truth-matching

GMSB “Good” efficiency vs.

conversion radius

Efficiency vs. angle and pt

cos (sorry…)

Accuracy of Good GMSB momentum reconstruction

1-track conversions

2-track conversions

Can we make use of 1-track conversions?

Accuracy of Good GMSB conversion radius reconstruction

1-track conversions

2-track conversions