Phase space integration diverges for ZZ production

[Wolfgang.Mader@cern.ch]

Dear SHERPAs

Triggered by a request from the ATLAS community, I'm looking at ZZ production using SHERPA-1.1.3. The process is defined as follows

%------------------------------------------------------- %-- Processes to calculate ----------------------------- %------------------------------------------------------- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % jet jet -> electron nu + n-jets % Process : 93 93 -> 90 90 90 90 Print_Graphs Order electroweak : 4 End process % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

using lepton containers. The divergence in the phase space integration occurs irrespective of whether I include cuts on the di-lepton invariant mass in (selector).

However, when looking at processes like

%------------------------------------------------------- %-- Processes to calculate ----------------------------- %------------------------------------------------------- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % jet jet -> electron nu + n-jets % Process : 93 93 -> 23[a] 23[b] Decay : 23[a] -> 90 90 Decay : 23[b] -> 90 90 Print_Graphs Order electroweak : 2 End process % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

or

%------------------------------------------------------- %-- Processes to calculate ----------------------------- %------------------------------------------------------- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % % jet jet -> electron nu + n-jets % Process : 93 93 -> 11 -11 11 -11 Print_Graphs Order electroweak : 4 End process % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

the phase space integration works just fine.

Thanks for your help

-Wolfgang

[Stefan Hoeche]

Dear Wolfgang,

in order to look into this issue we need information about the parton level selector. Please investigate this issue with a newer version of Sherpa as release 1.1.3 is not supported anymore

Best

Stefan

[Stefan Hoeche]

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