MadGraph5_aMC@NLO

ISR and BES implementation

Asked by Reza Jafari

Dear experts,

- I read paper 2108.10261, but I could not understand how to turn on and turn off the ISR effect in ee collision while using madgraph.
By this sentence "version 3.2.0 of MG5aMC includes in particular ISR in a native way" do you mean the ISR is on by default? Then how to turn it off?

- What about the beam energy spread (BES)?

I studied many materials, but I have not yet learned how to deal with ISR and BES in madgraph. Would you please help me through it? (I'm using madgraph version 3.5.0)

Thanks for your help in advance.

Best,
Reza

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Olivier Mattelaer
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Best Olivier Mattelaer (olivier-mattelaer) said : 		#1

Here is the relevant part of 2108.10261

Prior to running the code, the user
must specify in run card.dat that ISR and possibly beamstrahlung are to be included. This
is done by means of the lpp1 and lpp2 variables, which must be set equal to +3 (−3) for
an electron (positron) beam.

The user’s choice
of the ISR(+beamstrahlung) parametrisation are set in run card by means of the assignment
pdlabel=XXX. New ISR(+beamstrahlung) scenarios can be added by creating a new direc-
tory under Source/PDF/lep densities as discussed befor

So you have to set in the run_card
lpp1 and lpp2 according to the rule above
and then select the ISR(+beamstrahlung) with the variable pdlabel.

Cheers,

Olivier

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Reza Jafari (reza13) said : 		#2

Thanks Olivier Mattelaer, that solved my question.

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Reza Jafari (reza13) said : 		#3

Dear Olivier,

Thanks for your explanation.

Are there any user guide/ manual about these details?

Cheers,
Reza

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Olivier Mattelaer (olivier-mattelaer) said : 		#4

Nothing more than the appendix of 2108.10261, from which I copy-paste the line above

Cheers,

Oliveir