Changes between Initial Version and Version 1 of FAQ-General-10


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Timestamp:
Mar 20, 2012, 4:16:40 PM (12 years ago)
Author:
trac
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  • FAQ-General-10

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     3==== I generated an s-channel process p p > W+ > e+ ve, and in some events the W doesn't show up in the event record. Why is this? ====
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     5This is perfectly normal. Since you haven't used the decay chain syntax for the W,
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     7p p > (W+ > e+ ve) (in MG4) or
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     9p p > W+, W+ > e+ ve (in MG5)
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     11the W is not forced to be onshell - so when the invariant mass of e+ ve goes beyond the specified 15 widths (given by bwcutoff in the run_card) it is not included in the event file.
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     13Note that in general, diagrams with a forced s-channel propagator are no longer gauge invariant far from the BW peak, so the decay chain syntax is preferred.
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     15-- Main.JohanAlwall - 2011-01-29