Soft Photon studies

Problem: unexpected photon conversion enhancement peak at ~120 cm (radius). Geant simulations do not suggest any enhancement at such radius. TPC geometry does not have any extra material at 120 cm, but it is the distance where "outer" TPC volume starts. Please check the TPC diagram below:

TPC inner and outer sectors diagram

Possible solutions:

• Geant is OK, real data (Maker) is broken somehow
• Geant is OK, real data (track reconstruction) is broken somehow
• Real data is OK, Geant TPC geometry description is broken
• Real data is OK, Geant TPC signal reconstruction is broken

So far, we do not see any evidence that real data reconstruction is bad (we used exactly the same technique for high-pt electrons already). But, Geant description which is good for 1.0 GeV tracks might not be so good for 0.1 GeV tracks (see Gverify page, we have 1180 overlaps in Geant geometry)...

We did chi2 check of the electron/positron tracks.

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