The "Downstream Aluminum Problem"

The cos(theta) distribution changes, in places at the few percent level, when an aluminum plate is placed downstream of the detector. Little such change is seen in Geant simulations. This page describes the quest to find out why (and fix it).

"Downstream Aluminum in Geant" slides
Slides from the October 2003 Collaboration Meeting, summarizing the "Downstream Aluminum Problem".

Decay deltas and downstream aluminum and
Downstream Aluminum Effects and Delta Removal
Could the difference be in the way Geant generates delta particles? (Indications are: No.)

Downstream Aluminum and the Oct. 23 Tune Change
The beam tune was changed on 23 October 2002 (due to changes in power supplies etc. to the beamline elements). Did this change affect the cos(theta) spectrum between the "standard muons" dataset and the "downstream aluminum" dataset? (Indications are that, while there are effects, they are not enough to explain the "Downstream Aluminum Problem.)

Hitting DS Al in Geant
Checking whether the positrons are actually striking the aluminum in Geant and generating secondary particles (photons, deltas, etc). (They are.)

Last updated 03.10.30 by Robert MacDonald.

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