Track resolution in delphes_card_CMS.tcl

[jerdmann]

Dear Delphes experts,

I think I came across an error in the pT resolution for charged tracks in delphes_card_CMS. It quotes the following paper (1405.6569) and then implements this resolution function:

set ResolutionFormula { (abs(eta) <= 0.5) * (pt > 0.1) * sqrt(0.06^{2 + pt}2*1.3e-3^{2) +}

(abs(eta) > 0.5 && abs(eta) <= 1.5) * (pt > 0.1) * sqrt(0.10^{2 + pt}2*1.7e-3^{2) +
(abs(eta) > 1.5 && abs(eta) <= 2.5) * (pt > 0.1) * sqrt(0.25}2 + pt^2*3.1e-32)}

However, this resolution is much larger than what is shown in the quoted paper for charged pions (Fig. 16, bottom plot). I have implemented the following function by looking at Fig. 16:

set ResolutionFormula { (abs(eta) <= 0.5) * (pt > 0.1) * sqrt(0.01^{2 + pt}2*1.7e-4^{2) +}

(abs(eta) > 0.5 && abs(eta) <= 1.5) * (pt > 0.1) * sqrt(0.015^{2 + pt}2*2.6e-4^{2) +
(abs(eta) > 1.5 && abs(eta) <= 2.5) * (pt > 0.1) * sqrt(0.02}2 + pt^2*6.7e-42)}

Using this function, two-track resonances come out with a much more realistic mass resolution than before.

Please let me know if this is indeed an error in the card or whether I have misunderstood something.

Cheers and thanks,
Johannes

P.S.: I'm using Delphes 3.4.1.

[Michele Selvaggi]

Hi,

thanks for pointing this out and sorry for the late reply.
Indeed the resolution is worse than what is quoted. This was deliberate, as we manually worsened the resolution in order to have the right performance for particle-flow jet resolution. Indeed for resonances looking at single pions track the effect is bad as you noticed.
But we can't do much about it. You are free to change the resolution for your use-case.

Michele

[jerdmann]

Dear Michele,
sorry for only answering now that this is indeed helpful information for me.
Thanks!
Johannes