MET covariance matrix

[Giles Strong]

Dear Delphes authors,
I am trying to reconstruct the Higgs mass in tau tau decays using the standalone version of SVfit. This requires the covariance matrix of the MET, which I understand to be based on the pT resolution of objects.

I'm not sure how I would go about calculating the pT resolution of objects if they are reconstructed using the particle-flow algorithm, since the final resolution would, presumably, be a combination of the resolutions of the inner tracker and the calorimeters.

I'm wondering if the MET covariance matrix is something which can easily be returned by Delphes and if not, whether you have any recommendations for how I might go about calculating it.

Many thanks,
Giles

P.S. I am using version 3.2.2 of Delphes with the CMS detector card.

[Michele Selvaggi]

This is something not available right now, and honestly not sure if it will be.
This said is for each reconstructed particle, provided it is not a fake, you have access to the MC truth particle, maybe you can use the difference of (reco - gen) as an input to an algorithm that computes the covariance matrix in question. I cannot tell you more because I have no idea how the corr. matrix is calculated. You can have a look at examples/Example3.C for getting that info.

[Giles Strong]

Ok, thanks for the reply.
I'll take a look at that and see if I can come up with something.
Cheers,
Giles