In MC21a (corresponding to 2002 data) we will simulate multiple (four) beamspot sizes to
take into account the effect of luminosity levelling.
The "beamspot vs mu" profile which will be used in the pile-up presampling step is compressed down to a single entry per "step". (Each step corresponds to a single beamspot size (and lumiblock).)
This compressed profile is then scaled to the job size (with the MC21a profile the minimum supported simulation job size is 50 events). Steps are not used to trigger separate jobs in simulation.
Tested in Athena and AthSimulation. Matching output for old and new-style configuration.
NB Samples produced using this configuration should be merged using HITSMerge_tf.py with the
PyJobTransforms/postInclude.SortInput.py postInclude before being used as input to MC Overlay or pile-up Digitization. This postInclude ensures that all events in the output merged HITS file are sorted by lumiblock.