FWD Software

["Ogawa, Akio" <akio AT bnl.gov>]

Hello

SigmaMax is nothing to do with tracking. It is FCS Ecal cluster width along its long axis. It is expected to be around 0.5 for (single) photon or electron/positron clusters,  and larger for clusters containing 2 photons decayed from pi0 (how much larger depends on energy). 

SigmaMax is shown at middle right panel of 

  2022 : https://www.star.bnl.gov/protected/spin/akio/fcs/jpsi/dilep1.JPsi.0.png

  2026 : https://www.star.bnl.gov/protected/spin/akio/fcs/jpsi/20260603/dilep1...1.png

along with other variables I cut on, and in order I apply the cuts. 

SigmaMax cut is the last FCS cut I apply before any tracking cuts. Thus title of histograms I sent in previous email says this is plot “after“cut on Sigma Max (thus after all FCS cuts).

BTW bottom left panel of above shows TrackPt/EcalET ratio in 1d histogram, and 2022 plot shows a nice peak at 1.

It is sort of explained at the top of mother page ( https://www.star.bnl.gov/protected/spin/akio/fcs/jpsi/ )but I did send direct links the plots… Sorry. 

And that reminded me that I did loosen the Pt/ET>0.3 cut to 0 and probably I should raise it back up to at least 0.1. Thanks.

Akio

From: Van Buren, Gene <gene AT bnl.gov>
Date: Friday, June 5, 2026 at 12:29 PM
To: Ogawa, Akio <akio AT bnl.gov>
Cc: Brandenburg, Daniel <star-fwd-software-l AT lists.bnl.gov>
Subject: Re: [[Star-fwd-software-l] ] Pythia Jpsi sample

Is smaller sigma max == worse resolution, or better resolution?
-Gene

> On Jun 5, 2026, at 12:12 PM, Ogawa, Akio <akio AT bnl.gov> wrote:
>
> One thing I failed to point out yesterday was momentum resolution. See Pythia Jpsi plots for ET(fcs) vs PT(track) at right bottom :
> 2022 : https://www.star.bnl.gov/protected/spin/akio/fcs/jpsi/dilep.cut4.JPsi.0.png
> 2026 : https://www.star.bnl.gov/protected/spin/akio/fcs/jpsi/20260603/dilep.cut4...1.png
> Compare to “2022” (not sure how FwdTrackig was working at that time… was it using some true info still?), it is much worse and almost no pT resolution now...