Scan in mass

Registered by Olivier Mattelaer on 2011-10-18

Discussion on a implementation of a scan in mass.
This is a common request feature, and it's require for MW

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One thing that it might be easy to do, (and its important for MW5) is the possibility to scan over one (multiple) parameter.
This is a quite common request, and that's probably quite easy to do now. The problem is mainly to have an intuitive way to give the data.
If we allow this only for non-web use, we can do something like

define range MW range(60,80,2)
define range MZ [40, 60, 100]
define range MH math.sqrt(MW**2+MZ**2)

To be general, we should also add the possibility of dummy variable

define range MW range(60,80,2)
define range dummy1 range(-10,10,2)
define range MZ MW+dummy

And we can probably define some @1
define range MW range(60,80,2) @1
define range WW [1] * 5 + [2] *5 + [3] *5 + [4] * 5 @1
define range MH math.sqrt(MW**2+MZ**2)

Here the first value of MW will be linked to the first value of WW.

And maybe also allowing the following syntax
define range mass 6 [160, 180, 200]

What do you think?

The question is off course, what about the width?
Johan are they any progress in your width calculator?

Since 1.5.2, it's possible to have a (basic) scan:
create a file (lets say cmd.mg5) with the following content:
generate p p > t t~
launch #this ask question about configuration next lines will answer those
set MT 174
set WT Auto #compute the width of the top automatically (only 1->2 for 1.5.2)
set mass 25 125 # change the mass of particle 25 (higgs) to 125
set ptj 30 # change the cut on the pt of the jet to 30
set ebeam1 4000 #change the beam energy
set ebeam2 4000
done # start the computation of the cross-section/square matrix element
set MT 175
set WT Auto
done #start the second computation (with a different top mass)

Then launch it via the following command:
./bin/mg5 cmd.mg5

2.3.3 will allow a simpler syntax for scan over parameter space:

generate p p > t t~
set MT scan: [174,176,178]
set WT Auto

which will run automatically for three value of the top mass (and each time with the corresponding width) you can also use the python range function:
set MT scan: range(174, 180,2)
which is equivalent to [174,176,178] (python do not include the latest value)

You can have more than one "scan:" tag in the param_card, then a 2D(or more) scan will be performed.
If you want that the scan is syncronised over two parameters. Then you can use
set mh scan1: [100,200,300]
set wh scan1: [1e-3, 3e-2, 4e-1]
and the value of those two parameters will be correlated.


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