Turn off constraints

[bojohnson5]

I have a physics parameter that changes the shape of my expected signal. I want to be able to use shapesys to interpolate between different values of this parameter, but turn off the Gaussian constraint term. Is this possible anywhere?

[alexander-held]

The shapesys modifier implements bin-by-bin uncorrelated variations and has a Poisson constraint. If you want to remove the constraint you can turn it into a shapefactor, which lets the normalization float freely. This is also uncorrelated between bins, so the sample you apply this to can have any kind of shape.

Since you mention interpolation: in case you are thinking about correlated variations of bins, that can be implemented with histosys (which has a Gaussian constraint) and for that one it is not possible to remove the constraint. You could use expression functionality from #2579 to define a normfactor which scales linear combinations of different samples to manually build something that allows to interpolate between pre-defined shapes without a constraint term.