9:30am, checked the 100Hz pulser used in deadtime measurement of group 5,6,7,8. It turns out that when we are using a PS740 to fan-out the pulser, the output offset was not set to zero. It had about +34mV offset on the scope and on the multimeter, which is consistent with the PS vs. SH spectrum of these 4 groups. Set all to zero;
12:30pm, based on what we learned from above, also checked the offset of the other two 740s (used to form total shower, one 740 for 4 groups). Found all groups had an offset between +10 and +20mV. Group4 had an offset of -35mV. This is also consistent with what we see in data: group4 has a very low TS cut. Now set all offsets to zero. In order to keep the TS cuts roughly the same, increased the DH threshold from -80mV to -90mV.