K==> ΠoΠo Π resolution study

Number of images: 17
Created on: Monday 23 February 2004


The K==> ΠoΠo Π data simulated by Flyo have been reconstructed with two methods:
The first method (M1) evaluates the z-decay vertex imposing on the gamma mass a value equal to the missing mass of the K-Π system.
The second method (M2) reconstructs the z vertex as linear mean between the two nearest z-values choosen out of the three couplings obtained by constraining the gamma pairs to the neutral pion mass.

General pictures
Please clik on the figure to enlarge!
--mouse middle button--
thumbs/blk.png
Calorimeter population
thumbs/apk.png
Momentum of K as generated
thumbs/bchi1-2.png
Chi2 for pion mass test
M1 (solid) and M2 (dash)
thumbs/bzeta2.png
M2 Z vs Z-gen.
thumbs/bzv1-2.png
Riconstructed Z_vtx
for M1 and M2

Masses
thumbs/cdipion.png
Πo Πo
gener. and recon. in M1 and M2
thumbs/cggs.png
12 vs mγ34
only M1
thumbs/cmgg.png
mγγ
only M1
thumbs/cmgg2.png
mγγ
only M2
thumbs/cmk.png
K mas
Only M1
thumbs/Cmk2.png
K mas
Only M2

Resolution plots
thumbs/crismass.png
Πo Πo vs generated mass
thumbs/crisnor.png
M1: Πo Πo vs generated mass
normalized to k mass
thumbs/crisnor2.png
M2: Πo Πo vs generated mass
normalized to k mass
The last two scatter plots show that the two methods have similar behaviour on dipion mass resolution when the dipion mass is correted by the K mass difference between the reconstructed and the real one.

Results
thumbs/dmz.png
M(Πo Πo) vs zvtx
M1 and M2
thumbs/drisall.png
M(Πo Πo) resolution
thumbs/drisz.png
M(Πo Πo) resolution
at dipion mass (.27912)
The dipion mass resolution depends, for both methods (M1 and M2), on the dipion mass and on z decay and it is getting worse at the end of the decay region.
The resolution integrated on all decay path (second plot) is around 700 KeV for both methods,
while it could be less then 500 Kev at the dipion mass, eventually choosing a shorter decay region (less then 160 mt) as in the third plot. The method M1 seems to be slightly better then the other, however the result depends on the applied cuts.

Pisa 5.03.04
GmP
================================