Instructions for running the second level trigger

Responsible for this sheet: M. Medinnis,, phone: 4854

On-call expert

What to do if the expert is not reachable

Attempt to contact the subsystem coordinator.


How to run the SLT

Follow the instructions on the DAQ instruction sheet. Be sure that component "SLT" is enabled.


How to know that the SLT is giving sensible results

You can determine the SLT suppression by comparing the input rate as given by the "corrected rate" of the Trigger Control's "EVC Mon". To see this rate, click on the "EVC Mon" button of the Trigger Control Panel. The output rate is given on the "DAQ monitor". In it's present configuration, the suppression is varying between about a factor of 10 and a factor of 50. It's not possible yet to say what the suppression should be -- we need a little more experience. Furthermore, it changes as we add or subtract pretrigger and readout boards or change cuts.

The SLT histograms produces histograms which can be viewed by first starting a gatherer process which gathers histograms from the farm nodes and a display process.

To start the gatherer process:

To start the display process:

The display process has a primitive command line interface which allows you to display histograms of your choice. Type "help" for a list of available commands. "h/li" will give a list of available histograms. "h/pl N", where N is the histogram id displays the histogram. Note that the displayer is rather picky with syntax, e.g. it won't understand a command if it follows a blank. Soon, the root based display will become available so no effort is going in to improving this one. The "cycle on" command will repeat the next command you type in until you type "cycle off". Until you type in this next command, it will cycle indefinitely, giving you syntax error messages so don't be alarmed, just type in a command to display a histogram.

Examples of these histograms can be found in ~hbslt/herab/hbook/. See in particular slt_1335.hbook and slt_2449.hbook. These are hbook files and can be viewed with PAW. The x- and y-distributions are rather jagged and reflect the placement of readout and pretrigger boards. The pt-squared distributions should look fairly smooth. The mass plot (id 11) should show a prominent pi-0 peak.


What to do if I don't understand the instructions on this page

If you feel it could adversely affect the quality of the data being taken, contact the on-call expert. In any case, send an e-mail to the responsible for this page.