[Gdh_lowq2] EG4 Meeting Thursday

[Peter Bosted]

Hi,
    I wont be able to attend (doctor), but I thought you might like
to know that for eg1-dvcs we found two things:

1) EC/P peak position depends on P, but EC/(P-a) is essentially
constant. We found a=0.12 GeV, but you might well find a different
value (probably depends on where the ADC minimum values was set
in the sparcification). Having it flat makes it easier to find
the E/P cut. I recomend to only use a lower cut. Large E/P
can come from two particles close in space in time, but you still
want to keep the electron.

2) We found the target field is not aligned with CLAS by about
11 mr. This causes a dipole field which affects the reconstructed
theta in a sector-dependent way. Since you only suing sector 6,
this could introduce a bias in your values of W. If you want,
I can explain three methods that one can use to quickly find
out how big the mis-alignment is. Hopefully it is smaller for eg4.

Peter


Prof. Peter Bosted
email: bosted at jlab.org
phone: (757) 269-5851
address: Jefferson Lab Suite 6, 12000 Jefferson Ave, Newport News VA 23606

On Wed, 2 Dec 2009, Alexandre Deur wrote:

> Dear EG4 collaborator,
>
> We will have our next EG4 analysis meeting this Thursday (Dec. 3rd) at
> 10:00 am in room F224. Instructions to call-in can be found at:
>
> http://www.jlab.org/Hall-B/secure/eg4/deur/call_in_procedure.html
>
> Please let me know if you plan to attend.
>
> Best regards,
>
> Alexandre
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