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User name Reinhold
Log entry time 17:47:42 on September 01, 2009
Entry number 182909
This entry is a followup to: 182897
keyword=About interpreting TDC distributions: some facts about the trigger
When interpreting TDC distributions, you need to also consider these
things about the trigger:
* The charged particle trigger, CP0 for ungrouped, CP1-6 for grouped, is
formed by a 3/4 coincidence of H1X, H1Y, H2X, and LClow. So, one of the
four can be missing. If it's H1X, it cannot set the timing anymore.
* H1X timing has been set such that it should determine the timing of the
CP triggers. Likewise, CP timing has been set such that it set the timing
of the HKS triggers, which are CP_i & K_i, with K_i being the PID
triggers 2/3 of WC1_i & WC2_i, LChigh_i (i=0-6). However, This has been
set by looking at a large sample of detectors, especially for the
ungrouped trigger. Individuals with be off and thus timing determined by
someone else. That's not a problem, because eventually all that matters
are differences.
* The TUL meantimer has a delay line of 5 ns. Thus, if two signals are
off by more than 5 ns (this might only happen occasionally due to
jitter), the timing is determined by the leading edge of late signal.
Do not expect sharp peaks in the TDC distributions. Some of the or-ed
signals, be it grouped or ungrouped jitter by as much as 20 ns. I expect
this to show up in TDC distributions.
We will try to fine tune further of course. But there are limits.