[Olympus] Status of results and timeline

[Alexander Kiselev]

   Dear Norik,

> Now concerning the Q2 quality plot, which has a very clear interpretation, 
> and it puzzles me that nobody could understand it, because it is basic 
> relativistic kinematics from third year college physics, but I will 
> explain it in more detail:
> If you have already selected the elastic events (full set of cuts, 
> including the PID applied), then by making a binning over the lepton angle 
> you can define the average Q2 (<Q2>) (also stat. uncertainty for <Q2>) for 
> a certain angular bin. Here you have two opportunities how to define the 
> Q2: with the only lepton/proton measured angles (in our case preferable 
> due to good angular resolution) - Q^2_{exp}; with the measured angles and 
> momentum (worse due to bad momentum resolution) - Q^2{obs}.
> I also defined Q^2_{TH} using well known expressions for a scattered 
> lepton energy expressed via angle, with the beam energy  E_b=2010 MeV.
> Then I introduced the ratios: <Q^2_{obs}>/Q^2_{TH}(<\theta>), also 
> <Q^2_{exp}>/Q^2_{TH}(<\theta>). I assumed that in case we are really 
> selected the elastic events both ratios should be very close to unity, 
> this is, again basic physics.

   I believe I understand what is plotted, but I have difficulty to 
interpret this. Am I right, that background contribution in each theta 
bin is properly subtracted when you calculate Q^2 of "true" ep-elastic 
events by either of the two methods? Then (since there is obviously no 
bin-to-bin migration in theta at this point) the message is that momentum
measurement accounting screws up Q^2 calculation? And the screw up is
different for e+ and e- samples? If so, is this of any significance, given 
that Q^2 is calculated using proton theta only in both Brian's (thesis p.235)
and Rebecca's (thesis p.150) analyses (and both red and blue open circles 
on your plot indeed show sort of constant and very similar behaviour over 
theta within errors)?

   Best regards,
     Alexander.