[Primexd] [Revised Logentry] Accidentals in tagger, Be target

[Alexander Somov]

Hi Ashot,


The PS defines the trigger time (of the RF bunch where the
interaction occure).  For tagger counters, we see correlation
with with the trigger time.

Essentially, the PS is used as the real physics trigger
(the PS spectrum is not used at all).

Let's discuss it at the meeting today.

Cheers,
        Sasha




On 03/26/2019 03:31 PM, gasparan at jlab.org wrote:
>    Hi All,
>
>   When I stated that we better to look the time occupancy plot
>   from our physics trigger I meant process of identification of the
>   energy bin in the tagger for that particular event. As much as I
>   understand this is the simplified way of saying that. The PS may
>   have the similar occupancy but we will use the trigger timing and
>   look for the tagger ID number.
>   Another words, PS will define the INTEGRAL spectrum of the photon
>   beam on target, that we need but, event by event analysis is different.
>
>   Ashot
>
>
>> Hi Ashot,
>>
>> The fraction of accidentals depends on the reconstruction
>> channel (energy resolutions, etc.) and how you do physics
>> analysis (whether you perform kinematic fitting or simply
>> subtract accidentals, etc).
>>
>> Using the PS trigger and high-granularity counters,
>> implies that you reconstruct energy of the event
>> with the great precision (therefore you can study the fraction
>> of accidentals as a function of energy resolution).
>>
>> I doubt that we can do detailed reconstruction studies
>> of Compton and di-photons during this beam period. Running
>> at 200 nA is (probably) Ok.
>>
>> Another thing to consider, is the fraction of accidentals
>> in the CCAL .
>>
>>
>> Cheers,
>>         Sasha
>>
>>
>>
>> On 03/25/2019 10:43 PM, gasparan at jlab.org wrote:
>>>     Sasha,
>>>    Though it may not be much different but, it would be better to use
>>>    our experimental trigger instead of the PS trigger.
>>>
>>>    Thanks,
>>>    Ashot
>>>
>>>> Logentry Text:
>>>> --
>>>> Some quick (rough) estimates of the fraction of accidental hits in the
>>>> tagger (denoted as bg/sig in Fig. 2).
>>>>
>>>> 1. Consider PS trigger. Search for hits in the tagger around the PS
>>>> energy
>>>> in the window +- 1 GeV
>>>>
>>>> 2. Count number of hits correlated with the trigger time (signal).
>>>> Determine accidentals
>>>> from the side band of the time distribution (see Fig. 1). Subtract
>>>> accidentals
>>>>
>>>> 3. Fig. 2: fraction of accidental hits (in a  +- 1 GeV energy window)
>>>> in
>>>> the tagger as a function of the tagger energy
>>>>
>>>> I'll  check it later, just scratched the surface now.
>>>>
>>>>
>>>>
>>>> ---
>>>>
>>>> This is a plain text email for clients that cannot display HTML.  The
>>>> full
>>>> logentry can be found online at
>>>> https://logbooks.jlab.org/entry/3672169_______________________________________________
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>>>>
>>
>