Hi a few responses.
On Tue, 16 Mar 2004, Genya wrote:
> that reconstruction could affect the measured asymmetries.
assume 1 deg error on electron scattering angle reconstruction which I
think is realistic for us at the moment. this propagates to a few
MeV in electron momentum. both enter into Q2=4EE'sin^2(theta/2). 1deg in
theta causes 0.01GeV^2 in Q2. Asymmetry in parallel kinematics roughly
have Q2 dependence of 0.9/GeV^2 at the low Q2 range I am looking at now,
assuming a polarization of 20%. the asymmetry value I see is about -0.06
at Q2=0.15GeV^2. So the error caused by 0.01GeV^2 shift in Q2 translates
to >=10% of the observed asymmetry.
> Cross-sections is another matter. I do see that one of the sectors
I believe asymmetry is the difference between two cross sections.
> has low-momentum events cut off
> somewhat, but that could be attributed to different reasons. To begin
> with, does reconstruction take
> into account particles bending in the holding field?
typical track lengths are 3m. width of the target box is 10cm. holding
field ~ 300G, blast field ~3000G. so the effect of field integrated over
the path(or time spent on the path) makes the holding field effect <1%.
This archive was generated by hypermail 2.1.2 : Mon Feb 24 2014 - 14:07:30 EST