[Halld-cal] Changes to BCAL simulation timing

[Mark Macrae Dalton]

Hi guys,

The apparent variations in the velocity of light the BCAL fibers between layers are now understood as a geometrical effect which was not taken into account in the reconstruction.  We have for some time been using effective velocities in the Monte Carlo that differ from layer to layer, which has lead to noticeable problems with timing (layer 4 signals arriving first.)  The solution is to return to using a single velocity of light for all BCAL fibers based on measurements made at Regina and in beam tests.  Sean Dobbs has agreed to make this change to mcsmear and will do within days.  This will have minor effects on the BCAL timing.  Note that the BCAL timing is under active study at the moment and further changes are expected.

Best,
Mark Macrae Dalton



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