Description of the UFO models for HECO pair production

High-Electric-Charge Objects (HECOs) can be pair-produced via Drell-Yan and photon-fusion processes. Due to the large coupling, the perturbation theory breaks down. Nevertheless, one can resum the QED corrections at a UV fixed point for high electric charge and mass values.
The UFO models provided here describe both Photon Fusion and Drell-Yan processes, by including such resummation effects for spin-1/2 HECOs with electric charge q > 11e. By incorporating the resummation effects into the UFO models, we are able to provide reliable predictions for the production mechanisms under study. More details on the resummation technique can be found in ​https://arxiv.org/pdf/2310.17452.pdf

Two distinct models have been developed:

1. γ exchange UFO model: It takes into account the sole contribution from γ exchange, which is suitable for simulating both DY and PF processes.
   

2. γ/Z0 exchange UFO model: This model includes the additional exchange of the Z0 boson in DY production.
   

The UFO models incorporate two new input parameters:

• The multiplicity of the charge n which appears in the coupling definition g = ne, with e being the electron charge
  

• The cutoff energy scale parameter lambda
  

These parameters will define the value of the running HECO mass.

Commands for MadGraph5_aMC@NLO

1. γ-only exchange

• Drell-Yan

import model heco_spinhalf_photononly
generate p p > heco heco~
output DY_HECO

• Photon-Fusion

import model heco_spinhalf_photononly
generate a a > heco heco~
output PF_HECO

2. γ/Z0 exchange

• Drell-Yan

import model heco_spinhalf_withZ0
generate p p > heco heco~
output DY_HECO_Z0

Set run card and parameters

launch name_of_theoutput  ### replace name_of_theoutput accordingly, i.e. DY_HECO_Z0
set ebeam1 6500 ### beam 1 energy in GeV
set ebeam2 6500 ### beam 2 energy in GeV
set lpp1 1   ###   beam 1 type (1=proton)
set lpp2 1   ###   beam 2 type (1=proton)
set pdlabel lhapdf ### set the pdlabel argument
set lhaid 82000    ### set the pdf set 
set nevents 10000   ### number of events

set n 20 ### set the multiplicity of the charge 
set lambda 1000  ### set the cutoff energy scale in GeV