[Olympus] experiment MC comparison for MWPC lumi

[Jan C. Bernauer]

Dear Stan,

  this is excellent news. If I understand correctly, it means that the 
new target has very close to "full" density and that the luminosity 
calculation from slow control works. The remaining discrepancy is 
certainly realistic just from the uncertainty in the slow control lumi.

Best,
Jan


On 24.08.12 08:51, Belostotski, Stanislav wrote:
> Dear collegues,
> I am glad to report on a good agreement between MC (see the message
> attached below) and experiment for  MWPC Lumi monitor track
>   count rates ( taken @ 1 inverse nb, one arm):
>
>           in bending   out bending
> MC        6.55           11.52
> EXP       7.37           13.82
>
> The EXP track numbers were obtained  using Jan's track reconstruction
> program applied to MWPC hits for runs 4162 (inbend.) and 4137(outbend.),
> respectively.
> Statistical errors are negligible in both cases. As for systematics,
> there is some room to better determine the experimental numbers (to
> attach the proton tracks) as well as to finalize the MC calculations.
> Proceeding from above, it can be at least stated that our estimation of
> luminosity/target density looks quite reasonable and extracted lumi
> track data sample can be really used for lumi monitoring.
> With best regards StanB
>
>>
>>
>> On 23.08.12 08:46, Belostotski, Stanislav wrote:
>>> Dear Jan and all,
>>> having analyzed the MC file I found out that MWPC sensitive area is
>>> wrongly described: the sensitive area  given in MC is 15.5x15.5cm**2
>>> while  it is  10.5x10.5cm**2. This results in  higher count rate
>>> obtained from MC using MWPC tracks. Also, electron scattering angle
>>> distribution is twice wider then expected.Could you (Jan)  please
>>> correct that by inserting 10.5x10.5cm**2.
>>> The latter number is good enough as taken proceeding from experimental
>>> hit distribution and corresponds to MWPC drawings.
>>> The distance from the I.P. (269cm) is correct.
>>> In ideal case (point like target, no secondary re-scattering, no
>>> magnetic field) we have
>>> solid angle=1.52x10**-3 sr (one arm),
>>> the cross section found from MC, no magnetic field,   is 6206nb/sr so we
>>> end up with the
>>> integrated cross section 6206nb/sr x 1.52x10**-3 sr = 9.43 nb
>>>     which is equal to the count rate at integrated luminosity of
>>> 1/nb. For
>>> the in bending /out bending magnetic field I have (preliminary) obtained
>>> 6.55nb and 11.52nb, respectively, the numbers close to that obtained by
>>> Axel (not forget a factor of 2 for two arms). For the final numbers we
>>> need to generate two MC files (magnetic field +-) with correct MWPC
>>> dimensions. However I believe that the above numbers are very close to
>>> reality.
>>> With best regards StanB
>>>
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>>>
>>
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