Nik and I added singles events to the BLAST trigger, and tested it
with cosmics (runs 1806 and 1807). "Singles" means at least 1 TOF fired in
a sector. These singles were already coming out of the XMLU and being
counted in the scalers, they just weren't cabled to the trigger
supervisor. We added the cable, and also enabled these events in the
trigger supervisor.
The trigger supervisor (TS) code is now
~/pro2003/coda/crl/ts2_pro2003_pri_all8.crl . The first 8 input bits are
enabled, all in Common Strobe mode (so the OR of all the TOF meantimes
determines the event timing). Inputs 6 and 7 (the singles events, counting
from 1) are prescaled by a factor of 1000. There was a factor of 1001
prescale on input 4, but I have changed that to 1. The TS is set up so
that if multiple input bits have a signal, the event type is assigned to be
the lowest fired bit. For example, an ep elastic coincidence sets the 1st
bit as well as the 6th and 7th (the TOF singles); the event will be
assigned to trigger type 1. If you are interested in an inclusive cross
section, you'll need to analyze the singles events, apply the prescale
factor, and then add in any of the exclusive channels that apply.
Note that the scalers count BEFORE the signals go to the TS, so
that if PHYS0 counts, so will PHYS5 and PHYS6. The prescale factor does
NOT apply here, only in the TS. Note also that the scalers start counting
from 0, but the CODA trigger type counts from 1.
I don't know whether Tancredi got a chance to add trigger types 6
and 7 to the analysis codes before he left on vacation.
I also found a few bugs in physics.settings that I have fixed
(trigger bit 3 was requiring a neutron hit along with 0 TOF; the singles
bits were set for a neutron hit with 0 TOF; trigger bit 4 considered 2 RTOF
and 1 LTOF but not 2 LTOF and 1 RTOF).
To summarize the various trigger types:
The Cerenkov is NEVER required in the hardware trigger. The neutron wall
is only required in specific cases as noted below. Add 1 to the trigger
bit # to get the CODA trigger type.
Trigger bit # Trigger
----------------- ----------
0 exactly 1 left and 1 right TOF for selected combinations
(the ep elastic ridge)
1 exactly 1 TOF and a neutron with 0 TOF in the opposite
sector (en)
2 exactly 1 left and 1 right TOF for combinations not in bit 0
3 exactly 2 TOFs in one sector and 0 TOF in the opposite sector
4 exactly 2 TOFs in one sector and 1 TOF in the opposite sector
5 at least 1 LEFT TOF
6 at least 1 RIGHT TOF
7 flasher
Prior to today, only bits 0-3 and bit 7 were cabled. Bit 3 had a prescale
factor of 1001 applied, so essentially we have no data on that trigger.
(from an email from Zilu Zhou) :
2, data on all pion channels, in particular, the pi+ and pi- channel.
after reading emails from Adam/Aron and Chi, one has sense that
the elastic and quasi-elastic channels are all pretty much well-understood
or will be understood. however, there is a blank in all the pion channels.
are the triggers fine for pion-channels? are the CCs working for pion
channels?
do you lose pion events before CC in-efficiencies and cc hard-wired at
the
trigger level? are the neutron walls positioned without sacrifying
(e,e'n) to
help (e,e'n)pi+ at the 20-30 degree areas? are the pion event selections
reasonable from the given background in the forward directions? also what
about npi+ and ppi- channels in coincidence from photo-productions?
i am not concerned with all pion0 channels, but am concerned with
above all.
i do not have to say it as you all know perhaps better than i do, but
H(e,e'pi+)n, D(e,e'pi-)pp and D(e, e'pi+)nn will be good and easier
physics
for blast that nobody else can have. (i say easier, i mean that for
both e-p and
e-d elastic, you have to do them with extremely high precision to the
2nd or
3rd order, while pions are still at the zeroth or first order of
business.)
As you can see from the table of trigger types, some of the pion
channels Zilu mentions are partly included the data we have already taken,
others will be available now. I don't believe the hardware trigger is very
exclusive; finding various pion channels is more an analysis
issue. Michael Kohl can comment more on the location of the neutron detectors.
Karen
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