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Home » PANDA » PandaRoot » Analysis » entries at unphysical mass after vertex fit (lambda vertex fit with PndKinVtxFitter results in better fwhm but large tails in Lambda mass)
Re: entries at unphysical mass after vertex fit [message #18422 is a reply to message #17625] Mon, 17 August 2015 15:16 Go to previous message
Jennifer Pütz is currently offline  Jennifer Pütz
Messages: 47
Registered: April 2015
Location: FZ Juelich
continuous participant
From: *ikp.kfa-juelich.de
Hi everyone,

I found the same probelm as Albrecht. I ploted the difference of the masses of the daughters before and after the fit and saw that they are not exact needles. So I had a closer look into the PndKinVtxFitter and found that the four-momentum of the dauhgters after the vertex fit is set to (p_vtx, E_vtx). p_tx and E_vtx are the 3-momentum-vector and the energy of the daughter particle comming out of the vertex fit.
But E_vtx is not taking the mass hypothesis of the dauhgter particle into account. So I replaced E_vtx with sqrt(p_vtx^2 + m^2). (This was already implemented in the code but commented out.)
After doing that, the unphysical masses for Lambda0 have disappeared and the mass differences show now exact needles (see attached files).

Best,

Jenny


[Updated on: Mon, 17 August 2015 15:16]

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