Exercise 5: Change direction of beam

Object: Modify the initial beam direction, and measure spatial distribution of particles.

Similar to Exercise 4 using the block (not the cylinder), but change the angle or direction of the beam. Do this for 50 MeV gammas and electrons.

Do this at 15 and 30 degrees. Try to verify that the angle is being set correctly by measuring the centroid of all hits at the upstream face (left side in the above figure) of the iron block, and then calculating the mean angle from the event's starting point. You can do this by a scaler method or a spectrometry method. The latter could involve accumulating one histogram for the x coordinate and one for the y coordinate (VECT in common block GCTRAK) in GUSTEP and fitting to them in UGLAST (or interactively in PAW), or a single 2D y vs. x histogram and fitting to that.  The scaler method would involve the usual accumulation of sums of x and y values (or  r and theta) in GUSTEP and dividing by number of events in UGLAST.

It's also standard practice to histogram input variables, especially if they are varied run-by-run or event-by-event. In this case, you should set up angle spectra, say one for theta and one for phi.

Look for changes in results compared to Exercise 4.

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