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Opened 3 years ago

Last modified 3 years ago

#365 new defect

Incomplete variation weights for MEPS@NLO samples

Reported by: Frank Siegert Owned by: Enrico Bothmann
Priority: major Milestone: rel-2.3.0
Component: Hadron Decays Version: 2.2.1
Keywords: Cc: marek

Description

The newly implemented variation weights for MEPS@NLO samples fail to take into account the shower weight, which can come from the B/Bbar in (2.14) of arXiv:1207.5030 as long as CSS_USE_BWW=1 (the default).

This has two consequences:

1.) The variation weights are incomplete, i.e. a trivial 1.,1. variation does not always reproduce the nominal weight.

Trivial workaround for users of 2.2.1: Include the 1.,1. variation in your runs and multiply all variation weights by the following ratio (e.g. in HepMC terms assuming the default PDF):

event->weights[0]/event->weights["MUR1_MUF1_PDF261000"]

2.) The variation of the B/Bbar term is missing in the variation weights and would thus not give perfect closure. This will make even less of a difference, but should be fixed for completeness in the future.

In both cases the difference is (fortunately) beyond the NLO accuracy of the method.

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Change History (1)

comment:1 Changed 3 years ago by anonymous

1.) is fixed on rel-2-2-2 and trunk with r29367, r29366, respectively.

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