Mixed Event Background

Sep. 8, 2014 - Two photon mixed background

To model the background, we have taken the photon 4-vectors from other events and combined them with the photon 4-vectors for the true event. We double the statistics by mixing the first photon from the true event with the second photon from the out-of-time event as well as mixing the second photon from the true event with the first photon from the out-of-time event.

Below are (pi+, pi-, 2 photons) mass spectra from the carbon runs. The left plot is for the LD2 target and the right plot is from the carbon target. The black line is the data, the red line is the mixed event distribution, and the blue filled histograms are after background subtraction. The red line is normalized to the black in the region of 1.2 to 1.5 Gev/c².

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