[Olympus] Talk on Monday

[Norair Akopov]

On Wed, 12 Feb 2014, Michael Kohl wrote:

> Dear Norik,
Dear Michael,

Thanks for fast reply with useful comments.
>
> at large theta_e the yield is expected to go down fast, but I agree that you 
> might cut into the signal at large angle if is a constant cut tuned with the 
> yield at forward angles where the statistics is high.
>
> For the polar angle cut it would be good to plot the difference
> \theta_pr - f(E_0,\theta_e^{WC}), where f provides the proton angle from the 
> electron angle using elastic kinematics.
> This angular resolution likely varies a lot with the angle because the 
> protons at large angles correspond to low momentum hence suffer more multiple 
> scattering and energy loss. So in principle the angular resolution should 
> become better at large theta_e. However the lepton also becomes softer and 
> this may make the resolution actually worse.
>
> I recommend to plot the measured and calculated angle difference for each 
> theta_e bin like your *_resol.pdf, but for the angle difference, then 
> parametrize the cut ...

I was just thinking to install \theta_e dependent correlation cut ..
>
> It would also be worthwhile to monitor the difference in lepton and proton 
> vertex for each of these bins.

Well, I'll check this also, but I'm not expecting to see remarkable Zv 
diff. dependence on \theta_e..
>
> Best regards
>  Michael


Best regards,
Norik
>
>
> On Wed, 12 Feb 2014, Norair Akopov wrote:
>
>> 
>> Dear Michael,
>> 
>> I added the polar angles correlation cut and produced new plots, which are 
>> located again on:
>> 
>> http://www.desy.de/~akopov/Olympus_Monday_Meeting
>> 
>> you can compare the old plots with the momentum resolution at different 
>> \theta_e angular bins: electron(positron)_resol.pdf done W/O applied polar 
>> angles correlation cut with the new plots: electron(positron)_resol_new.pdf 
>> where this cut is applied. On the lower right panel (\theta_e&\theta_pr 
>> double plot) you can see that this wide background area seen on old plots 
>> is now almost removed.
>> The meaning of applied cut should be clear from the plots: 
>> electron(positron)_theta_q2.pdf,
>> where the comparison of \theta_e and \theta_pr distribution as well the Q2 
>> dsitributions are plotted with and W/O this additional cut applied.
>> At any place I'm writing e.g  \theta_pr=f(E_0,\theta_e^{WC}) I mean that 
>> f() is just expression based on elastic kinematics conditions.
>> 
>> You can see that background clearly seen for angular distributions (at high 
>> angles for lepton and at low angles for proton) W/O this cut applied is 
>> essentially suppressed after the cut was applied.
>> 
>> Then I estimated the rate of expected selected (close to elastic) events 
>> sample with all cuts described in my talk W/O polar angle correlatrion cut 
>> and with. This is effi.pdf file, where you can see, that unfortunately with 
>> this additional cut the expected staistics at high \theta_e angles, where 
>> we should reach the smallnest values of \epsilon is essentially decreased..
>> 
>> I'm now thinking on another form to introduce the polar angles correlation 
>> cut to select the data. It seems the used ratio of 
>> sin(\theta_pr^{WC})/sin(\theta_pr=f((E_0,\theta_e^{WC}) to be close to 
>> unity within 3 \sigma is too strong.
>> 
>> Best regards,
>> 
>> Norik
>> 
>> 
>> 
>
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