[G12] CC time vs SC time question

[Valery Kubarovsky]

Hi All,

Michail Osipenko made an extensive study of the CC timing calibration.
Please take a look to the CLAS note 2004-020 and 2006-009.
He propose the method for timing calibration and found that timing cut is very
important for the suppression of pion contamination. The claim that the Cherenkov time resolution is very bad is just wrong. You need carefully calibrate the detector before using timing information from CC.
Osipenko claims that one of the
contributions to the wrong electron ID is the random hits in the CC. To make space and time matching 
for electron candidates he significantly reduced the pion contamination. I recommend to read
these two notes if you want to improve the electron ID using Cherenkov counter.

Valery

----- Original Message -----
From: "Michael C. Kunkel" <mkunkel at jlab.org>
To: "Michael Paolone" <mpaolone at jlab.org>, "Johann Goetz" <theodore.goetz at gmail.com>
Cc: "g12" <g12 at jlab.org>
Sent: Tuesday, July 14, 2015 10:26:02 AM
Subject: Re: [G12] CC time vs SC time question

Thanks everyone.

BR
MK
----------------------------------------
Michael C. Kunkel, PhD
Forschungszentrum Jülich
Nuclear Physics Institute and Juelich Center for Hadron Physics
Experimental Hadron Structure (IKP-1)
www.fz-juelich.de/ikp

On 7/14/15 9:23 AM, Michael Paolone wrote:
> The CC time calibrations were never included in the last round of cooking.
>   Even then, only the T0 coefficient was "calibrated" by subtracting 750ish
> ns from every PMT to bring the mean of the difference to 0.  A study was
> never done on a PMT by PMT basis, and the higher order timing coefficients
> were never looked at.
>
> If the CC timing is important for someone's analysis, then they will
> likely have to do a new calibration.  But most lepton analyses, like
> Johann said, can use the EC timing with much better resolution if needed.
>
> -Michael
>
>
>> The CC timing is so poor in resolution that this hardly matters to anyone.
>> I believe we have no incentive to align timing in the CC to the event
>> time.
>> The EC timing is sometimes used as a substitute for a missing TOF hit, but
>> that's a relatively small effect. Also, what are the units on time? Both
>> 50
>> ps and 50 ns do not make sense for the TOF (should be 100-200 ns). This
>> should be normalized to the event time (RF or tagger or even ST would
>> work).
>>
>> On Tue, Jul 14, 2015 at 3:09 AM s.schadmand <s.schadmand at fz-juelich.de>
>> wrote:
>>
>>> my guess is that these are the absolute times and only the magnitude of
>>> the difference in ns needs to make sense. who has a smaller absolute
>>> time
>>> entry depends on cable lengths and readout, common start/stop or
>>> clocking?
>>>
>>>
>>>
>>>> On Jul 14, 2015, at 07:25, Michael C. Kunkel <mkunkel at jlab.org> wrote:
>>>>
>>>> Greetings,
>>>>
>>>> Michaela Schever, Masters student at Forschungszentrum Jülich working
>>> with g12, has asked me a question that puzzles me.
>>>> Please look at
>>>>
>>> https://clasweb.jlab.org/rungroups/g12/wiki/index.php/CC_Study#Tuesday_July_14.2C_2015
>>>> Notice the y axis is the cc_time and the x axis is the sc_time.
>>>> The question was why is the cc time greater than that of the sc time,
>>> considering the TOF is located after the CC and also why the negative
>>> slope?
>>>> I did look in the code and noticed that these quantities are grabbed
>>> from the TBID bank, which has both cc and sc time in ns.
>>>> I also looked into some of the calibrations and did not see anything
>>> striking that would answer this.
>>>> Please help us understand this.
>>>>
>>>> BR
>>>> MK
>>>> ----------------------------------------
>>>> Michael C. Kunkel, PhD
>>>> Forschungszentrum Jülich
>>>> Nuclear Physics Institute and Juelich Center for Hadron Physics
>>>> Experimental Hadron Structure (IKP-1)
>>>> www.fz-juelich.de/ikp
>>>>
>>>> _______________________________________________
>>>> G12 mailing list
>>>> G12 at jlab.org
>>>> https://mailman.jlab.org/mailman/listinfo/g12
>>>
>>>
>>> ------------------------------------------------------------------------------------------------
>>>
>>> ------------------------------------------------------------------------------------------------
>>> Forschungszentrum Juelich GmbH
>>> 52425 Juelich
>>> Sitz der Gesellschaft: Juelich
>>> Eingetragen im Handelsregister des Amtsgerichts Dueren Nr. HR B 3498
>>> Vorsitzender des Aufsichtsrats: MinDir Dr. Karl Eugen Huthmacher
>>> Geschaeftsfuehrung: Prof. Dr.-Ing. Wolfgang Marquardt (Vorsitzender),
>>> Karsten Beneke (stellv. Vorsitzender), Prof. Dr.-Ing. Harald Bolt,
>>> Prof. Dr. Sebastian M. Schmidt
>>>
>>> ------------------------------------------------------------------------------------------------
>>>
>>> ------------------------------------------------------------------------------------------------
>>>
>>>
>>> _______________________________________________
>>> G12 mailing list
>>> G12 at jlab.org
>>> https://mailman.jlab.org/mailman/listinfo/g12
>>>
>> _______________________________________________
>> G12 mailing list
>> G12 at jlab.org
>> https://mailman.jlab.org/mailman/listinfo/g12
>>
>

_______________________________________________
G12 mailing list
G12 at jlab.org
https://mailman.jlab.org/mailman/listinfo/g12