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Small positive chi2 values in PndKinFitter [message #14682] Tue, 30 April 2013 11:13 Go to previous message
Lu Cao is currently offline  Lu Cao
Messages: 77
Registered: February 2013
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Dear all,

In the simulation (#18621) of pbar p -> Ds+ Ds-; Ds- -> K+ K- pi-; Ds+ ->eta e+ nue; eta -> pi+ pi- pi0, I did the mass constraint fitting to the pi0 candidates with PndKinFitter. All the chi2s are pretty small with the mean value of ~0.001. This also happens in the case of eta.

I noticed the previous topic discussed by Albrecht about the negative and extremely small chi2 in PndKinVtxFitter. 79&S=7cee6febef5676d17dc9e3154e1269e2

Considering the formula for chi2, the small values may be due to a large sigma in the denominator.
Does anybody have some solutions or hints to improve it?
or is there any way else to understand this problem?

Thanks in advance.
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