less events converted in .lhe

Asked by federica on 2020-10-14

Hello, I have implemented a model of ALPs in Calchep. I have simulated 25k events with MC. Then with event_mixer procedure (../bin/event_mixer 25000 25000 .) I have converted the file.txt (given by MC simulation) in file.lhe and very less events are converted. Do you know why? How can I solve it? Thanks

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Alexander Belyaev (alexander.belyaev) said :
#1

What is the cross section for your process and how many subprocesses you have?
This information is important to clarify what is going on in your particular case.

in your case

../bin/event_mixer 25000 25000 .

has the 1st and 2nd argument as Luminosity[1/fb] and e nEvents respectively

I will generate number of events = min(sigma x Luminosity[1/fb] , nEvents )

So, if the cross section is very low, say 10^-3 fb

then it will generate min(10^-3 fb x 25000[1/fb] , 25000 ) = 25 events

If you you like to generate 25000 event for sure, just put luminosity very high, say 1E10
i.e.

../bin/event_mixer 1E10 25000 .

But I need more info about your process in order to help for sure

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federica (fedegiacchi) said :
#2

Thanks for you answer.

Sure:
    for example 2.559E-06 pb, this is the cross-section of one point where I have ~60events converted.

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Alexander Belyaev (alexander.belyaev) said :
#3

This explains why you have few events generated:

25000 x 2.6E-3fb = 65 events are expected

this is exactly what you have got

Alexander

On 2020-10-14 14:41, federica wrote:
> Question #693464 on CalcHEP changed:
> https://answers.launchpad.net/calchep/+question/693464
>
> federica posted a new comment:
> Thanks for you answer.
>
> Sure:
> for example 2.559E-06 pb, this is the cross-section of one point where I have ~60events converted.
>
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federica (fedegiacchi) said :
#4

ok so for having 25k, I have to modify (As you said before) the first number - Luminosity - in the conversion procedure.

Thanks a lot.
Federica