[Frost] meeting tomorrow

[Michael Dugger]

Sungkyun,

You might be seeing a "pre-selection" effect. When you define the reaction 
as being "gamma p -> p pi+ pi-" you have to make some sort of cut. This 
means that only those events that you pre-select as candidates are further 
processed in determining the "missing" mass values for pi+ and pi-.

-Michael

On Fri, 23 Jul 2010, Sungkyun Park wrote:

> Hi Eugene,
>
>   I have found the missing mass of pi0 in topology gamma p -> p X and butanol target.
>   The pi0 mass 162 MeV
>
>    Michael Dugger -> pi0 (no momentum restriction) = 163 MeV
>                                pi0 ( momentum > 600 MeV) = 157 MeV
>    Hideko Iwamoto -> pi0 ~ 168 MeV
>    Jo McAndew     -> pi0 ~ 176 MeV
>
> I also tried to find out the missing mass of pi+ and pi- in topology  gamma p -> p pi+ pi-
> The pi+ mass I found is 144 MeV and the pi- mass is 142 MeV.
> It is very strange why pi0 mass has a big difference with real particle and pi+ and pi- has a very similar value in the same code.
>
> Best Wishes
>
> Sungkyun Park
> Florida State University
>
>
>