Using PAW - A Brief Tutorial

A complete description of PAW is, as the standard cop-out goes, beyond the scope of this text. However, in order to get people started, we will supply a short cookbook on doing some very simple data display and cuts. If you are not familiar with using PAW at your institution, it is advisable to seek local assistance, probably from a friendly high-energy physicist, on how to get it running on your machine. On most machines you simply type PAW, however there are often details concerning getting the graphics output to the correct place and knowing what type of graphics device your implementation of PAW is expecting. We will simply assume that you have managed to get PAW running and are now staring at the prompt (note that in what follows we show all inputs in upper case, if you are on a UNIX machine they will have to be typed lower case):

PAW $>$

At this point you should type:

PAW $>$ HIST/FILE 50 HBOOKSM.NTP

This opens the file HBOOKSM.NTP for PAW to work with identifying it with the number 50 (this number is arbitrary). This file contains a single N-tuple, which was arbitrarily numbered 500 by the NTPR titles bank in titles files provided. So you can now, for instance, type:

PAW $>$ NT/PRI 500

This will print on your screen the contents of N-tuple 500 (the only one you presently have), giving you the names of all the variables and their extreme values (see the NTPR titles bank for information on what is being saved). If you now type:

PAW $>$ NT/PLO 500.NHITS

the program will plot a histogram of the variable NHITS in the graphics window. You can of course also plot any of the other variables. You can also make scatter plots of one variable against another, type:

PAW $>$ NT/PLO 500.RFIT%REVENT

This will make a scatter plot with the generated radius REVENT on the x-axis, and the fit radius RFIT on the y-axis. If you want a little more information on the plot, type:

PAW $>$ GRA/OPT STAT 111111

Now plot NHITS again, note the box added to the corner of the plot telling you the number of events, the mean and the variance of the distribution. You can place cuts on the variables, for instance type:

PAW $>$ NT/CUT $1 NHITS.GT.60.

This has created cut with id $1, which excludes all those events with NHITS less than 61. Note: in some older versions of PAW, the cut id did not have the leading$. Now type:

PAW $>$ NT/PLO 500.NHITS $1

You now see NHITS plotted but with cut $1 imposed, so only those events with more than 60 hits are plotted. Now type:

PAW $>$ NT/PLO 500.RDEV $1

PAW will now plot RDEV, the radial deviation of the fit, for those events which pass cut $1. Cuts can be combined, for instance type:

PAW $>$ NT/CUT $2 NHITS.LT.75.

PAW $>$ NT/PLO 500.NHITS $1.AND.$2

Now plots only those events where NHITS lies between 61 and 74. One can also combine cuts with OR instead of AND, with the obvious result. When finished with the file type:

PAW $>$ CLOSE 50

To free hbook.ntp to be written over. To exit, type:

PAW $>$ EXIT

We have had a lot of trouble with PAW creating unkillable rogue X11 processes if the session is logged off without killing it, so just a hint: exit PAW before logging out. The above is just the tip of the iceberg, but it should be enough to get started. For further info, consult the PAW manual and check out the PAW web page from cern (http://asdwww.cern.ch/pl/paw). Also look at:-

..snoman/n_nn/examples/analysis_kumac.doc

where we hope to list some useful KUMAC files (i.e. PAW command files) that have been written for SNO.