[Olympus] experiment MC comparison for MWPC lumi
Douglas Kenneth Hasell
hasell at MIT.EDU
Sun Aug 26 14:23:21 EDT 2012
Hi,
I think this is good progress. While the rates are far from final it is a=
good starting point.
I suggest that the MWPC work together with J=FCrgen and the GEMs to get a =
single analysis for the 12 degree detectors in good shape for the readiness=
review in 4 weeks. It should be possible to get tracks in the GEMs and MW=
PCs in coincidence with a proton track in the WCs.
For now I would normalise everything to the slow control luminosity which =
maybe wrong but is stable over time and we can later correct this to a bett=
er luminosity measurement from the symmetric Moeller. This can be done for=
the four combinations of beam and magnet polarity and some very crude rati=
os formed.
Of course this has to be compared to Monte Carlo studies for acceptance. =
There are also efficiency questions to be investigated. But I would not tr=
y to simulate detector response and digitization as there isn't time now. =
Let's just get some initial results.
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 =
=
On Aug 26, 2012, at 8:28 AM, Belostotski, Stanislav wrote:
> Dear Michael, Jan, and all,
> I agree that the results are promising, however the numbers obtained =
> are by far not the final ones.
> To answer to Michael's question, there are some considerations below.
> The detection efficiency is C=3DC_geom x C_trig x C_track,
> here C_track is overall track reconstruction efficiency including MWPC =
> digitization. As Jurgen mentioned last Friday, number of MWPC tracks =
> surpasses those of GEM by some 30% same track reconstruction program =
> being used. It is not yet certain that the ep elastic scattering tracks =
> only were selected such that C_track (exp) could have been both larger =
> and less than 1.
> In the MC, to calculate the lumi count rate, we find the C_geom and =
> averaged over MWPC1-3 acceptance cross section, assuming that within a =
> MWPC sensitive volume detection efficiency is constant (=3D1), as well as =
> C_trig=3D C_track=3D1.
> Next step in the MC is to include digitization and track reconstruction =
> program in the same way as the latter treats an experimental data =
> sample, while C_trig is to be experimentally determined.
> In the exp data analysis joint GEM/MWPC track reconstruction, associated =
> proton track inclusion and additional kinematic cuts to make as clean =
> as possible the final data sample are soon to come.
> Then we hopefully come to the final conclusion.
> With best regards StanB
> =
> =
> =
> On 24.08.2012 17:36, Michael Kohl wrote:
>> 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 experiment=
al
>>>>>> 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=3D1.52x10**-3 sr (one arm),
>>>>>> the cross section found from MC, no magnetic field, is 6206nb/sr s=
o we
>>>>>> end up with the
>>>>>> integrated cross section 6206nb/sr x 1.52x10**-3 sr =3D 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) obta=
ined
>>>>>> 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
>>>>>> =
>>>>>> _______________________________________________
>>>>>> Olympus mailing list
>>>>>> Olympus at mit.edu
>>>>>> http://mailman.mit.edu/mailman/listinfo/olympus
>>>>>> =
>>>>> =
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>>>> =
>>> =
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>> =
>> +---------------------------------------------------------------------
>> | Dr. Michael Kohl, Assistant Professor and Staff Research Scientist
>> | Physics Department, Hampton University, Hampton, VA 23668
>> | Jefferson Lab, C117, 12000 Jefferson Avenue, Newport News, VA 23606
>> | Phone: +1-757-727-5153 (HU), +1-757-269-7343 (Jlab)
>> | Fax: +1-757-728-6910 (HU), +1-757-269-7363 (Jlab)
>> | Email: kohlm at jlab.org
>> | Cell: +1-757-256-5122 (USA)
>> |
>> | Deutsches Elektronen-Synchrotron DESY, Bd. 66, Rm. 6,
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