# EFT dim8 aQGC decomposition in VBS pp->4l2j : Sum of cross sections does not match with the EFT prediction

Dear experts,

I am writing you regarding the "decomposition" of some anomalous Quartic Gauge Couplings samples (details: https:/

Following the general idea that the EFT predictions can be split up as the sum of the SM, the SM-EFT interference (linear term) and the pure EFT (quadratic term) contribution, I'm generating independent pure samples by using the "New Physics" parameter (NP==0 for SM, NP^2==1 for pure SM-EFT interference and NP==1 for pure QGC). The cross-terms (interference between EFT operators) are expected to be 0, as all the operators, except ft0, are 0. I am also generating a sample including all the contributions by using NP=1 (same as NP<=1) in order to compare the cross section of this sample with the sum of the independent samples.

The cross sections for

pp > j j l+ l- l+ l- QCD=0 QED=6

with ft0=5e-13 are the following:

pure SM, NP==0: xsec = 0.0005771 +- 2.049e-06 pb

pure aQGCs, NP==1: xsec = 0.0002521 +- 5.606e-07 pb

pure interference SM-EFT, NP^2==1: xsec = 1.187e-05 +- 4.084e-08 pb

SUM: 0.00084107 pb

while the cross section of the "all in one" sample is,

NP=1: xsec = 0.0007203 +- 2.18e-06 pb

We have a difference of ~14%. So, my question is if this behaviour is expected and if not, which of two results is more reliable, the sum of the independent samples or the sample with all the contributions?

(I can attach the banners of each run for more information)

Thank you in advance,

Alexandros

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