generating events with three body decays

Can you give me some more information:

Is this the only decay that you include in your batch file? Or, are there others?

Can you give me:
* the number of events requested.
* the number of production events produced (e+,e-->~n1,~n1).
* the number of decay events produced (~n1->2*x,~sv4).
* the number of final events produced after connecting production and decay.

What version of the batch program are you using? (This is printed to stdout when you start the batch program.)

The version of the batch program is calchep_batch version 1.7

This is the only decay I include in the batch file. There are 60 decay modes generated by the symbolic calculation of this 30 are kinematically allowed.

In the batch file I request 100000 events in the batch file.
The number of production events produced is 101580
The number of decay events is 509997 for each allowed decay mode.
The final number of events is 1106.

It looks like the batch program is working properly. Even if one decay dominates over the others, there are more than enough decay events produced. I apologize that until this is fixed, you will probably have to request more events than you want.

Sasha, why is the event_mixer not producing enough events? My thought is that it is randomly assigning production events to decays that are not present (1->2 decays) and throws them away when it doesn't find them. There must be a better way to deal with this.

Dear Ajr-williams,

could you provide the information about
the cross section about the production
and production+decay for this process which you can easily see in the web-browser?

My suspicion is that the cross section after decay is non-physically low:

batch interface aims to generates events for your requested number,
*but* for for max luminocity 10^9 fb^-1
The Max lumi limit is chosen to very high but finite to avoid situation
when the program is caught in the infinite loop.

Most likely you have chosen extremely rare decay, such that the total cs
for production x decay is of the order of 10^-6 fb (since you have only ~ 1K events generated.

If you still need to generate events for your process even with this very low CS,
let us know please and send us your model+batch file, so we can test and improve
approach on the event generation.

Cheers,
      Sasha

Hi,

I think that you are right the production cross section is 4.5099e-03 fb and after decays is 1.1060e-06 fb.

Is it possible to change the max lumi limit when running the batch file or will this cause a problem

The reason that I am interested in this process is not for a collider study but I need the decays of the particles including hadronization which I am doing in pythia. This requires collision events which pythia can work with but the cross section itself is not important.

Ideally I would like to produce the particles with as little momentum in the lab frame as possible but I think this will decrease the cross section even further.

Perhaps you know of a better way to do this? I can provide the batch file and model if this is useful.

Sure,
just edit

bin/run_batch

file and change
$max_lumi = 1e+9;
line to
whatever you need

to have

max Nevents = your_cs * $max_lum

For example, for your case

$max_lumi = 1e+12;

will do the job

Regards,
     Sasha

Neil,
thanks this is a good point,
could you add this to "Help" please, or to "#" comment in the template, or both?
I guess this solves the problem nicely.
Cheers,
 Sasha

The last answer solves the problem

Thanks Neil Christensen, that solved my question.