Inclusive "P b bbar" cross section

[Frank Siegert]

Sherpa's cross section for pp -> P b bar around the Z->b bbar peak doesn't reproduce the one in Madgraph if the following cuts are applied:

• pT(photon) > 200 GeV
• pT(b) > 50 GeV
• pT(bbar) > 50 GeV
• |eta(photon)| < 2.5
• |eta(b)| < 2.5
• |eta(bbar)| < 2.5
• dR(photon, b) > 0.6
• dR(photon, bbar) > 0.6
• 89<m_{b bbar}<93

Using cteq6l1 and a fixed fac/ren scale=mZ, Madgraph gives 0.007710 pb, while Sherpa gives 0.020742 pb. If I select the resonant diagrams only, i.e. pp -> P Z[b bbar] then Sherpa (0.005917 pb) and Madgraph (0.005869 pb) agree well.

I attach four setups:

• Madgraph inclusive (inc_proc_card.dat + run_card.dat)
• Madgraph resonant (cut_proc_card.dat + run_card.dat)
• Sherpa inclusive (Run.inc.dat)
• Sherpa resonant (Run.cut.dat)

I have checked that the generated diagrams are the same. If I haven't overlooked something the above mentioned cuts should be implemented in both setups (and since the resonant XS is consistent, this seems to work).