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Re: Vertex fitters' problems [message #14888 is a reply to message #14847]

Thu, 20 June 2013 15:47

Ralf Kliemt
Messages: 508
Registered: May 2007
Location: GSI, Darmstadt

first-grade participant

From: *gsi.de

Hi.

I did some fixes to Rho and the fitters. We had deeply hidden bugs...

Now, I ran the same simulations just as you did and modified the analysis macro to my liking (attached). The outcome is strange BUT:
A) ChiVtx and KinVtx give somewhat similar vertex resolutions. They should as these are the same (P.Avery) Algorithm programmed by different colleagues.
B) POCA is comparable to the fitters above - because it is the seed value for them. I looked it up and the KinVtx actually converges, so I blame the few excess energy available in your system. Both the kaon and pion tracks will almost move along with the CMS.
C) The PRG fitter (Billoir algorithm) produces better results. Wonderous to me but there we go; maybe its in the algorithm. Both fast and full fit give the same resolution where I would blame the kinematics again.

I hope I could solve the issues now.

Cheers
Ralf

PS: The overly good resolutions of the KinVtx came from the fact that the vertex vector was always zero and the negative MC coordinates were plotted.

Attachment: vtxtest_ChiVtx.pdf
(Size: 24.80KB, Downloaded 464 times)
Attachment: vtxtest_KinVtx.pdf
(Size: 24.80KB, Downloaded 414 times)
Attachment: vtxtest_Poca.pdf
(Size: 24.80KB, Downloaded 450 times)
Attachment: vtxtest_FastPrg.pdf
(Size: 25.01KB, Downloaded 446 times)
Attachment: vtxtest_FullPrg.pdf
(Size: 24.95KB, Downloaded 444 times)
Attachment: match_kinvtx.C
(Size: 12.03KB, Downloaded 468 times)

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[Message index]

		Vertex fitters' problems By: StefanoSpataro on Thu, 06 June 2013 12:40
		Re: Vertex fitters' problems By: Ralf Kliemt on Thu, 06 June 2013 13:02
		Re: Vertex fitters' problems By: Simon Reiter on Thu, 06 June 2013 17:09
		Re: Vertex fitters' problems By: StefanoSpataro on Thu, 06 June 2013 17:11
		Re: Vertex fitters' problems By: Ralf Kliemt on Thu, 20 June 2013 15:47
		Re: Vertex fitters' problems By: L. Zotti on Fri, 21 June 2013 18:43
		Re: Vertex fitters' problems By: L. Zotti on Thu, 25 July 2013 16:22
		Re: Vertex fitters' problems By: StefanoSpataro on Fri, 26 July 2013 13:26
		Re: Vertex fitters' problems By: StefanoSpataro on Fri, 26 July 2013 14:48
		Re: Vertex fitters' problems By: Simon Reiter on Fri, 26 July 2013 14:55
		Re: Vertex fitters' problems By: L. Zotti on Mon, 29 July 2013 11:11

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