with the trunk version 20077. In the latest trunk the function GetMcTruth() returns null pointer, than the trunk cannot be used.

We have simulated 10k ppbar->D*+D*-->D0pi+D0barpi-->k-pi+pi+k+pi-pi-, we have used MC truth index to identify the kaon- and the pion+ of the D0 (we have not touched the d0bar).

We have uploaded all the relevant macros, you have only to modify the path of the DEC file in the sim macro.

We run PndKinVtxFitter, PndVtxPoca and PndVtxPRG and compared the results. We were able to find a tutorial only for PndKinVtxFitter. The tutorial for PndVtxPoca and PndVtxPRG is missing then we hope we are using them in the proper way.

Please check the code.

Vertex residuals reco - mc (in cm) and chi2 for PndKinVtxFitter:

Vertex residuals reco - mc (in cm) and chi2 for PndVtxPoca:

Vertex residuals reco - mc (in cm) and chi2 for PndVtxPRG:

These are the obtained resultion values:

|X res | Y res | Z res | PndKinVtxFitter | 2um | 2um | wrong and asymmetric | PndVtxPoca | 400um | 400um | 400um | PndVtxPRG | 60um | 60um | 100um |

Then...

PndKinVtxFitter is obtaining very very very narrow distributions on X and Y. How is it possible? Z distribution is screwed. Chi2 is very low.

PndVtxPoca has too large resolution values, does not work. Decent chi2 maybe.

PndVtxPRG has more reasonable values, even if I believe they are a bit large. It is much slower than the others, most probably because of the 10 iterations, but w/o a tutorial we were not sure about which number to use. Chi2 too low.

Still not checked composite particles (i.e. D*)

Then...

What to use? Could you please take a look?

Many tanks in advance.

Laura and Stefano

]]>

I'm on the Monte-Carlo list filling thing right now.

As for the fitters, I wonder how the 2um are possible.

The 400um of the POCA may be normal, as it is a coarse approximation.

The PRG fitter is limited in its precision as the algorithm itself is designed to be faster.

Ralf]]>

I'm working on similar simulations and was also planning to compare these three fitter. But I'm wondering what

RhoCandidate

TCandidate

Greetings Simon]]>

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. ]]>

Looking in your analysis macro, I found you just missed one "break" at line 273. Actually with this modification, I got some better results from the ChiVtx fitter.

Moreover, cleaning the sample looking at the FitStatus flag, I got the following resolution:

PndChiVtxFitter x:32um y:52um z:138

PndVtxPRG (full) x:61um y:60um z:103um

PndVtxPRG (fast) x:60um y:61um z:103um

Plots for PndChiVtxFitter:

Plots for PndKinVtxFitter:

Plots for PndVtxPoca

Plots for PndVtxPRG

1)fast:

2)full:

Still to be understood why resolution are different in x and y for the PndChiVtxFitter.

Do you think this results are reliables?

The KinVtxFitter and the Poca one still give strange results.

For what concern the kinematics, actually the kaons and the pions from the d0-meson are well separated in angle, how you can see here:

]]>

Please can you upload the correction? (here in attachment).

Moreover, I found a lot of negative chi2..... Does somebody of you know how can this be possible and can have a look on this problem?

Thanks in advance,

Regards

Laura]]>

root [0] TVector3 e(1,2,3) root [1] TVector3 f=(1,2,3) root [2] e.Print() TVector3 A 3D physics vector (x,y,z)=(1.000000,2.000000,3.000000) (rho,theta,phi)=(3.741657,36.699225,63.434949) root [3] f.Print() TVector3 A 3D physics vector (x,y,z)=(3.000000,0.000000,0.000000) (rho,theta,phi)=(3.000000,90.000000,0.000000) root [4] TVector3 d root [5] d=(1,2,3) (class TVector3)41869040 root [6] d.Print() TVector3 A 3D physics vector (x,y,z)=(3.000000,0.000000,0.000000) (rho,theta,phi)=(3.000000,90.000000,0.000000)

and without a single complain...]]>

I'm trying to look at that chi2, but will take me some time..]]>

these are the main results that I got.

Resolution on x: 32 micron

Resolution on y: 54 micron, why is it different from x?

Resolution on z: 113 micron.

Chi2 still some negative values: do you have suggestions on how to decide what is the best candidate in case of combinatorials?

Mass of the D0 before and after the fit: after the fit we got a low number of D0 under the central peak

Best regards,

Laura]]>