Violation in Mixing

3.3 Studies on data 87
0.504
0.502
0.5
0.498
0.496
0.494
observed Ks candidate masses
0.492
0 1 2 3 4 5 6
ks momentum (GeV)
0.008
0.007
0.006
0.005
0.004
0.003
0.002
0.001
observed Ks candidate mass resolution
0
0 1 2 3 4 5 6
ks momentum (GeV)
0.504
0.502
0.5
0.498
0.496
0.494
observed Ks candidate masses
0.492
0 1 2 3 4 5 6
ks momentum (GeV)
0.008
0.007
0.006
0.005
0.004
0.003
0.002
0.001
observed Ks candidate mass resolution
0
0 1 2 3 4 5 6
ks momentum (GeV)
Figure 3-7. Top plots: invariant mass as function of the reconstructed momentum of the Ã Ë in block 1 (left)
and in block 2 (right). Bottom plots: invariant mass resolution as function of the reconstructed momentum of
the Ã Ë in block 1 (left) and in block 2 (right). The on-resonance data-Monte Carlo comparison is presented:
the empty dots come from the Monte Carlo sample and the black points come from the on resonance data.
At the same way, we can look at the efficiency as function of both �Ö and the reconstructed momentum of
the Ã Ë : see Fig. 3-10.
To find out what is causing the drop between � and � cm in the efficiency as function of the decay length,
the same study has been done using a �Ö value taken from the Monte Carlo truth. The figure (3-11) shows
two gaps: the first between 2 and 3 cm that is the same we see in data and Monte Carlo without using the true
�Ö, while the second is between 12 and 15 cm due to a the Monte Carlo association failing in that region.
This result shows that the vertexing is not introducing this gap in the efficiency shape.
In order to check the momentum dependence of the efficiency the shape of the Ã Ë momentum in �� events
has been checked: figure (3-12) shows a nice agreement between �� from data and from Monte Carlo in
the Ã Ë reconstructed momentum. The Ã Ë momentum in �� events in data is obtained from a side-band
subtraction and then an off-resonance subtraction from the on-resonance distribution.
Ã Ë RECONSTRUCTION AND EFFICIENCY STUDIES