Simulation with PLUTO for pp@1.25GeV

Here, I will present the status of pp@1.25GeV PLUTO simulation. The generated events are very close to the events from Anja and Witek. There are just some small changes.
Just to remind : Page from Witek and Anja
In our simulation, we do not have 2 pion events, which should vanish with missing mass cut. But all other cross section values are taken in the same table. The second difference is about the momentum smearing. We use either the standard Geydar's parametrisation or the Geydar's factors adjusted to real resolution. Otherwise, all the parameters for generation are equivalent.

Ideal Resolution	Realistic Resolution

We apply an asymmetric cut on the missing mass. This reduces more the pi0 contribution because the missing mass is higher than for delta Dalitz decay. The black line represent all pe+e- combinations
The red line represent pe+e- combinations, from events with delta Dalitz decay, calculated with the proton from the delta decay (top left hand corner for 2D-hist)
The green line represent pe+e- combinations, from events with delta Dalitz decay, calculated with the proton which is not from the delta(top right hand corner)
The blue line represent pe+e- combinations, from events with pi0 Dalitz decay, calculated with the proton from the delta decay(bottom left hand corner)
The pink line represent pe+e- combinations, from events with pi0 Dalitz decay, calculated with the proton which is not from the delta
We can see that the acceptance is quite the same for both proton from the delta decay and the other one in case of delta Dalitz decay and for small missing masses in case of pi0.(bottom right hand corner)

We can notice also that the effect of resolution is bigger for low missing energies than for higher one. This can be understood by the fact that, if the missing energy is low, the momentum of the detected proton must be high. So, the error on the momentum will be high.

With the actual resolution, the missing mass cut is not enough to reduce pi0 contribution. The missing energy cut allows a better reduction of the pi0. It seems however important to improve the resolution as the first step.

-- EmilieMoriniere - 08 Feb 2007