T11 beam transport simulations with Decay Turtle
In order to parametrize the muon contamination in our low
energy (< 2 GeV) pion sample one has to employ a reasonably accurate beam
transport simulation through T11 and T7 beam optics. This is the first
attempt to accomplish this task for T11 using the Decay Turtle program, a
well-known tool for beam transport simulations.
I have extracted the beam
magnet parameters from CERN PS documentaion and cross-checked them with
a number of CERN PS beam experts, so I assume they are accurate.
The only bit which I am missing here is the exact values of the magnet
apertures. At the moment I am using just my guesstimates to define apertures but
I am working on getting the true values asap.
The plots shown below are for 1 GeV beam of pions and muons (from pion decay).
The distributions are obtained at 30 meters downstream of the target, more or less
where plane 0 is.
The first plot shows the momentum distribution of pions (top histogram) and
muons (bottom histogram).
The second plot shows two-dimensional lego histograms of
momentum, P, versus horizontal extent of the beam , X, (left column) and
horizontal angular divergence of the beam, X', (right column) for pions and
muons
The next plot is the same as the previous one but
for the vertical extent and vertical angular divergence of the beam
One can see from the plots above that muons
occupy much larger phase space
than pions due to the
pion decay kinematics which makes their separation
from the low energy pions harder.
Things to do:
- Find out and use the true values of magnet apertures
- Simulate T7 beam line
- Use correct collimator settings when making comparison between MC and specific
runs
- Use Turtle MC as an input to GMINOS to generate beam event kinematics (GUKINE)