Transcript EmSim.ppt

EM Studies
(X.C. and E.C.S. – Oct 3, 2002)
The Engineering Module is simulated according to the geometry description in
LAT-TD-00828-02 and it consists of
• A four-tray tracker
• a full calorimeter
• no ACDs and other supporting structures.
Three types of events were generated:
SIGNAL : 17.6 MeV photons to mimic van der Graaf source (for now use point source)
BACKGROUND: 3 GeV muon to mimic high energy cosmic ray muons (cos2q dist. from -1 to 1 )
BACKGROUND: 100 MeV muons to mimic low energy cosmic ray muons (cos2q dist. from -1 to 1 )
It is critical that the EM be placed horizontally so that, as will be shown later, the
reconstructed event direction can be used to reject cosmic muon backgrounds.
Muon background rates compared with gamma signal rate.
Assuming photons have a source rate of 1 Hz .
(Numbers can only be taken as rough estimates.)
Event Type
Trigger rate (Hz)
Reconstruction rate (Hz)
17.6 MeV photons
0.019
0.016
3 GeV muons
4.24
2.46
100 MeV muons
0.033
0.025
Need to cut down muon flux by at least 3 orders of magnitudes
Angular distribution
reject
Theta is the angle between
reconstructed particle
direction and the horizontal z
axis, gamma travels along the
z axis.
Event Type
Total
Recon
After
Cut
e
17.6 MeV g
811
652
80%
3 GeV m
1232
17
1.4%
100 MeV m
1222
27
2.2%
After angular cut
Tracker Energy
Number of tracks
CAL Energy
Summary
A scintillator veto is highly recommended. Looks like there no troubles in
implementing that
Because of low gamma rate and low triggering efficiency of the EM, we may need to
run a few days (2 or 3) to accumulate enough statistics.
Next steps are:
• quantify spectrum measurement
• understand effect of second peak (~ 10 MeV) from van der Graaf
• estimate energy resolution
• look at PSFs
• Update SVAC EM Plan