=====Muon Trigger Coincidence Timing=====
The Soudan veto shield has been running for quite a long time now and it was recently realized that there is a problem with the correlation of times between different MUXes (front-end DAQ cards) and the NMM Symmetricom times.  In particular, events which are contrived to be coincident (via a common pulser input) are apparently not coincident.  The origin of this is not well understood but has been narrowed to some discrepancy in the clearing of the MUX card counters. The data that ran around 07/25/2013 with a muon trigger on the NMM have the correction times necessary for each mux listed in the table below:

^Station^MUX^Delay from NMM (sec)^Delay from NMM (musec)^
|SW|1|18|20|
|SW|2|18|20|
|SE|1|17|20|
|SE|2|1|20|
|NW|1|18|20|
|NW|2|18|20|
|NW|3|1|20|
|NE|1|33|14|
|NE|2|1|14|
|NE|3|1|14|

The fact that these values appear correlated is somewhat of a mystery.  The current hypothesis for how these arise is a lack of proper clearing of the MUX counters.  It would be understandable if all the shifts were the same (suggesting a problem in the hardware programming).  Or perhaps it would be understandable if we always saw the same shift for an individual MUX, which is also not the case.  

In any case, after correcting for these apparent shifts using a special data-startup procedure involving sending correlated pulser events to all stations and the NMM in an 15s on, 1m off pulse train, we can get the correlated muon timing seen below. 

Timing from just the NW station:

{{:nmm:timing_dat:timefromnmmnw_072413_center.png?500|timing distribution for coincident muons in the NW station}}

Zoom of above:

{{:nmm:timing_dat:timefromnmmnw_072413_zoom.png?500|timing distribution for coincident muons in the NW station}}

Timing from all stations:

{{:nmm:timing_dat:timefromnmmall_072413_center.png?500|timing distribution for coincident muons in the NW station}}

Zoom of above:

{{:nmm:timing_dat:timefromnmmall_072413_zoom.png?500|timing distribution for coincident muons in the NW station}}

Six day run (NW only):

{{:nmm:timing_dat:timefrom_shifted_muons_072413.png:?500|timing distribution for coincident muons in the NW station}}

Six day run, zoomed (NW only):

{{:nmm:timing_dat:zoomed_timefrom_shifted_muons_072413.png:?500|timing distribution for coincident muons in the NW station}}