MC cross section tables

Two-column files with phase space and corresponding cross section in pb. For instance, the total cross section in the Pythia 8 flat sample is around 1-2 mb. For comparison, the total MB cross section at CMS is 100 mb at 13 TeV.

How to get a cross section

TWiki

High-order calculations for many standard model cross setions can be found on the TWiki. There are dedicated pages for top and Higgs processes. Check these first!

Computing it yourself (GenXSecAnalyzer)

GenXSecAnalyzer is a CMSSW module that extracts cross section information stored by the Monte Carlo generator at generation time. Since it comes from the generator, this number suffers from the same limitations as the generator itself. In particular, cross sections calculated at leading order may suffer from very large scale uncertainties and be subject to large correction factors. For complicated processes such as top or Higgs production, it is best to rely on externally computed numbers when available.

The DAS ntupliser module is configured to run GenXSecAnalyzer by default. The cross sections can be found by reading the job log.

See also the instructions

MCM

McM is primarily used to produce samples. There is a cross section field, but updating it is a manual process and errors are possible. Don't trust this information.

AVOID IT AS MUCH AS POSSIBLE