LAT Newsletter contributions from Beam Test Team
Issue 8 - submitted december 4
Beamtest :
Intro with coll meet slides and workplan
Simulation status: we are moving to the v71215p0 release, with the following major changes
- pass5 variables from the current event classification analysis are added to the Merit Tuple and replace old pass4 variables; this allow a subsystem specific comparison of data and MC variables that are relevant for the background rejection
- the high energy SPS runs (E>5GeV) were re-simulated with the correct pressure (0.1bar) and gas (He) in the cerenkov detectors along the H4 line
analysis :
– full comparison between geant4 and EGS5.
– adding extra material along the beamline : The average overestimation between data and MC is about 7%, but it is higher for the first layers of the calorimeter than for the last. This seems to indicate that the showers start earlier in the data than in the MC, tracing extra material along the beamline that is not described in the simulation. We have tested this idea by simulating different pressures in the Cherenkov. We have used these simulations to look for the amount of extra-material that could account for the current disagreement between data and MC. When considering most all the SPS configurations, we find that 10% of radiation length would help, though it doesn't solve the discrepancy for all configurations and only 5% of radiation length seems necessary for the tracker variables.
– pass5 variables are well reproduced except for the calorimeter related variables. This is certainly due to the transverse size of the showers which is larger in the data than in the MC.
– high energy electrons : how much can we be affected by badly reproduced variables and how we can modify them.
Issue 7 - submitted 16 October
Simulation status: we have now a stable BTRelease and are producing all the interesting configurations with that. We are following a list of golden runs that people mostly used for analysis and for which we have already tuned the MC and data beam spots. For each run we automatically produce a system test report which allow instant comparison of data and MC, and post it in the runs list. A prototype higher level data-MC agreement matrix was presented and is being improved. The Low-Energy Geant4 simulations which seemed to produce a different energy deposit in the CAL are now back to the standard energy deposit we get with standard Geant4 libraries, after having fixed a bug which Francesco and Johan identified. A thourough material audit was conducted for the CAL, and modifications will have to be made in the detector geometry which will probably add some minimal extra radiation length wrt to the current model.
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