Checking dE/dx calibration made by Yi Guo for pp500  in Run XI I again paly attention to "extra band" observed in plot dE/dx versus momentum.     

This "extra band"  which was previosly associated with "wrong Anode Voltages in so-called bad runs" is pretty well matched with hypothesys that the tracks reconstructed in this band are coming from two pions close to each other (see red line which is marked as 2π). I don't observe this extra band in AuAu.  Some traces of this band can be seen in the next plot for Run IX.

I have suspicion that :

1. We do see effect of StTpcHitMaker After Burner introduced in Run X which trys to merge splitted clusters.
2. Altro parameters have been change in Run X/XI with respect to Run IX. This change was an attemp to make clusters more compact. The observed effect is opposite

My proposal to rerun production for dE/dx calibration with and without After Burner to see its influence.

Run XI dE/dx versus momentum.

Run IX dE/dx versus momentum.