scan over a parameter

Asked by Mihail Chizhov

At present CaclHEP allows to scan over a MODEL parameter. Sometimes it is useful to have a scan over other input parameters, like c.m. energy and so on. For example, in order to calculate PDFs uncertainties it is necessary to run over PDFs sets:
LHA:MSTW2008lo90cl.LHgrid:0:1, LHA:MSTW2008lo90cl.LHgrid:1:1, and so on... Is it possible to implement this feature?

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Neil Christensen
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Neil Christensen (neil-christensen-qft) said :

I understand the suggestion. It is a good idea. I can not do it right now as I am trying to get an important paper done. Contact me again in a month or so and I will see if I can do it then.
Best wishes,

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Best Neil Christensen (neil-christensen-qft) said :

Dear Mihail,

I apologize for my pessimistic answer before. I have implemented the scan over energy. It is in version 1.12 of the batch program. You can find it at:

I have run a few tests on it and it seems to work. If you find any problems, please let me know. Here are the basic instructions. You can scan over a parameter that is not a model parameter. So, for example, you could add the lines:

Run parameter: rtS
Run begin: 7
Run step size: 1
Run n steps: 2

to your batch file even though rtS is not a parameter of the model. (You could name it something different if you like.) Then, the momenta can be made functions of the scan parameters. For example,

p1: 1000*rtS/2
p2: 1000*rtS/2

This will plug the scan value of rtS in and then calculate the value before running CH.

Let's start with this improvement and make sure it works properly. Then, I will work on your other request of scanning over pdf sets.

Best wishes,

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Mihail Chizhov (mih-c) said :

Thanks Neil Christensen, that solved my question.