[Olympus] PRL paper

[Michael Kohl]

Dear Stan,

let me try to chip in a few remarks which are hopefully helpful.


On 1./ regarding pion production:
Background rates are asymmetric w.r.t. pi+/pi-, however each pion is 
almost symmetric w.r.t. e+/e- (ignoring TPE).
Pion backgrounds would have to be either of type where a pion (pi0) is 
produced in addition to ep but not detected (highly but not totally 
suppressed by missing mass analysis), or by misidentification of pi+ as 
e+, or pi- as e-. These are suppressed even more because there would be no 
proton in coincidence.
If at all, we are dominated by the former which is mostly e+/e- 
charge-symmetric. In reality the nature of observed residual backgrounds 
is more random-like, from the particle flux from upstream to downstream.
Residual background was identified and subtracted, but not modeled in MC.
The size of residual background is now mentioned.

On 2.:
The MIE method is described in detail in Axel's thesis, and as far as I 
can tell, it correctly takes the intensity dependence of the coinc 
ee&ep (prop L^2) over single ee (prop. L) into account.

On 3.:
Many crosschecks were done with the MC, including e.g. generating and 
propagating an e+p sample but analyzing it as e-p and vice versa, and by 
switching the toroid back and forth for the MC samples.
The generator was extensively tested and validated against ESEPP.

Best regards
   Michael



On Mon, 7 Nov 2016, Belostotski, Stanislav wrote:

> Dear Douglas and all,
> I am surprised not to find ANY reaction to my comments sent 04.11.2016,
> neither in the paper text nor at least by a mail. To remind, the
> comments  are attached below.  Regards StanB
> P.S. Sorry, I will not participate the meeting today
> ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
> 1.Table 1.
> A couple of items :
> -uncertainty due to beam positions and slopes is missing ;
> -"geometry". What does geometry mean? Is that alignment imperfection?
> "Elastic (event) selection and bgr subtraction".
> There is no discussion in text about background which  at large angles
> is mostly related to pion production. Remember, the latter is charge
> asymmetrical. I can assume that the pion contribution is small but at
> least a few lines on pion production is needed.
> 2.Page 3, left, paragraph "The integrated luminosity...."
> These MIE , as stated in this paragraph, are coincidences of small angle
> ep scattering and Moller or BhaBha coincidence events.So they are random
> coincidences(?). Then they must be corrected for the beam intensity
> variations(?). Or this is my ignorance (?).Ref.29 does not help ( "to be
> published").   Why just  small angle ep scattering is not  usable for
> normalization?
> I presume similar questions will be put by a referee.
> 3. It is well known that kinematic constrains used for event selection
> effect strongly on RC contribution. Extraction of net TPE effect from
> the ratio is only possible  if these constrains are strictly identical
> for e+ and e-. On the other hand the e+/e- acceptances are different.In
> a bin in Q**2 this is of course solved applying eq.1. The question is
> still how much false asymmetry can be resulted from imperfections of MC
> simulation. Was the MC model tuned somehow and cross-checked?
> I think we need a few lines on that point.
> 4.page4 with Fig.2.correct misprint at line 4. left   (simulation)
> 5. My opinion on ranking in the author list is in details in my previous
> mails.
> ..............................................................
>
>
>
> On 07.11.2016 2:09, Douglas K Hasell wrote:
>> Dear Colleagues,
>>
>> 	Attached is what is I hope the final version of the PRL paper.
>>
>> 	Just a reminder: the collaboration meeting is tomorrow, Monday, November 7, at 10:00 EST (16:00 CET).
>>
>>                                                       Cheers,
>>                                                               Douglas
>>
>> 26-415 M.I.T.                                  Tel: +1 (617) 258-7199
>> 77 Massachusetts Avenue                        Fax: +1 (617) 258-5440
>> Cambridge, MA 02139, USA                       E-mail: hasell at mit.edu
>>
>>
>>
>>
>>
>>
>>
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| Dr. Michael Kohl, Associate Professor and Staff Research Scientist
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