this is to examine any differences in centroid positions between runs from earlier during run9 vs later run9 due to changes in the magnetic field.

Runlists:

For the earlier set, the runs used are (from Brian's priority list):

(May 21 - 22)

184 10141008
185 10141010
186 10141011
187 10141013
188 10141018
189 10141019
190 10141020
191 10141023
192 10141025
193 10141026
194 10141027
195 10141030
196 10141031
197 10141032
198 10142011
199 10142019
200 10142029
201 10142031
202 10142032
203 10142034
204 10142035
205 10142036
206 10142041
207 10142042
208 10142043

The later runs used are:

(June 21 - 22)

604 10172094
605 10173007
606 10173008
607 10173009
608 10173012
609 10173013
610 10173014
611 10173015
612 10173048
613 10173051
614 10173053
615 10173055
616 10173077
617 10173078
618 10173081
619 10173082
620 10173083
621 10173084
622 10173087
623 10173088
624 10173090

Here is the fitted histogram for PT range of 2.0-30.0 (earlier runs):

For the same PT range but the later set:

 The pion centroid (p4) changes only slightly (~1%), which doesn't explain the large difference in gains for run 9. This indicates that the change is not gradual degradation in the detector but most likely a change that happened quickly. Also just to point out, the eta peak width increases (from earlier to later) by ~44% while the pion peak width decreases by ~5%.