CalcHEP

QCD scale defenition

Asked by pytnik89

When I want define "alpha Q" as (T1-T2)^2 or something with sign "minus" I got CH Error 139. So Is there any way to define QCD scale as I mentioned?
Thanks...

Ivan

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Alexander Pukhov
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Best Alexander Pukhov (pukhov) said : 		#1

Yes, it is bug. '-' is treated wrongly in this place.

Open file c_source/num/qcdScale.c
Starting from line 64 you should see
=====
     case '-':
     case '+':
     case '*': p=malloc(strlen(p1)+strlen(p2)+10);
======
It should be
=======
     case '-': p=malloc(strlen(p1)+10);
                sprintf(p,"(-(%s))",p1);
                return p;
     case '+':
     case '*': p=malloc(strlen(p1)+strlen(p2)+10);
===============
CalcHEP reader treats "-" as a unary operation, an operation of change of sing. Not as operation of subtraction.

Thanks a lot for your note. I'll update the code today.
Alexander Pukhov

PS: I guess you mean T3-T4, not T1-T2. T1 and T2 ( transverse momenta of on incoming particles) have not sense in CalcHEP.

Revision history for this message
pytnik89 (pytnik89) said : 		#2

Thanks a lot for your help, it's solved my problem! I mentioned this behaviour 1 year ago, but didn't have strong necessity in it, and now all is good.

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pytnik89 (pytnik89) said : 		#3

Thanks Alexander Pukhov, that solved my question.