Unexpected event yields in the decay channels of pp->ZZjj->4ljj

Is your muon massless or massive?

> On 15 Jan 2020, at 16:03, Alexandros Marantis <email address hidden> wrote:
>
> New question #688013 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/688013
>
> Dear experts,
> I'm writing you regarding some discrepancies I notice between the number of events in the different flavoured decay channels of ZZ during the generation of a pp->4l2j sample.
> I am using a BSM dim-8 model (SM_LS012_LM017_LT012_Ind5_UFO: http://feynrules.irmp.ucl.ac.be/wiki/AnomalousGaugeCoupling) in MG5 v2.6.5 to generate the SM (QCD+EWK) contribution of the VBS pp->4ljj process (where l=e,mu), assuming that all the operators are zero.
> By using loose cuts during the production of 5k events, I get 25-25-50 percentages of the decay channels, as expected. i.e:
> pp->ZZ->eeeejj events: 900
> pp->ZZ->mmmmjj events: 931
> pp->ZZ->eemmjj events: 1920
> Trying to limit the events into my fiducial volume, I set some tighter cuts during the generation (mjj>300 GeV, etaj<5, 60<mll<120, drll>0.2, WBF Delta_eta_jj > 2, pt_j>30 ) and this leads to the discrepancy I mentioned:
> pp->ZZ->eeeejj events: 251
> pp->ZZ->mmmmjj events: 233
> pp->ZZ->eemmjj events: 4356
> The 2e2m channel contains ~18 times more events, while I'm expecting just 2!
>
> In order to validate the results, I generated independently these three decay channels using the same cuts.
> The cross sections of the processes correspond to the above problem:
> dim8 VBS pp->4e2j xsec = 1.94E-05 pb
> dim8 VBS pp->4m2j xsec = 1.94800E-05 pb
> dim8 VBS pp->2e2m2j xsec = 3.35700E-04 pb
>
>
> My question is, if you find this behaviour normal and how can you explain that.
> Is there a specific cut that forces MG to prefer the 2e2m channel instead of the SFOS channels?
>
> p.s
> In my proc_card_mg5.dat, I'm generating the processes in this way:
> generate p p > j j mu+ mu- mu+ mu- QCD=2 QED=6 T0==0 T1==0
> add process p p > j j e+ e- mu+ mu- QCD=2 QED=6 T0==0 T1==0
> add process p p > j j e+ e- e+ e- QCD=2 QED=6 T0==0 T1==0
>
>
> Thank you in advance,
> Alexandros
>
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Hi Olivier,
massive.

I'm suspecting that these cuts
mmll ! min invariant mass of l+l- (same flavour) lepton pair
mmllmax ! max invariant mass of l+l- (same flavour) lepton pair
are causing the problem.
Do these cuts apply to all possible lepton pairs or just to the leptons from the same parent?

Hi,

Then try to reduce the muon mass to see if the problem decreases in that limit.
You should be sensitive to that parameter. (It is possible that some EFT operator are proportional to the mass of the leptons or something like that)

Cheers,

Olivier

> On 16 Jan 2020, at 12:18, Alexandros Marantis <email address hidden> wrote:
>
> Question #688013 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/688013
>
> Status: Answered => Open
>
> Alexandros Marantis is still having a problem:
> Hi Olivier,
> massive.
>
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> contact for MadGraph5_aMC@NLO.

Thanks Olivier Mattelaer, that solved my question.