[Olympus] experiment MC comparison for MWPC lumi

[Michael Kohl]

Dear Stan, all,
indeed this is a milestone.
I suppose the efficiencies were all assumed to be unity, which adds in 
some uncertainty, too?
Best regards
    Michael


On Fri, 24 Aug 2012, Jan C. Bernauer wrote:

> 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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>>>> Olympus at mit.edu
>>>> http://mailman.mit.edu/mailman/listinfo/olympus
>>>>
>>>
>>> _______________________________________________
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>>>
>>
>
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