[G12] CC time vs SC time question

[Michael C. Kunkel]

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
>>>>
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