[Clas12_rgh] [EXTERNAL] RGH meeting February 17

[Anselm Vossen, Ph.D.]

Hi Marco,

we had some more discussions with Gerard on the effects playing a role here and 'it is complicated'.
As Nilanga showed, for short bars, a significant fraction of the photons comes from Cherenkov light, but since this is emitted at a specific angle, this is very much deendent on geometry and what is covered by the sensors.
In general, if you have wider bars, you have more photons which increases the resolution. I think there is also a geometric effect, as it becomes more likely for the photon to not hit a wall, I am not sure if that is completely absorbed into the area factor.
The other thing we learned from Nilanga's studies, is that a lot of the resolution has to do with the readout chain. I.e. the rise time of the readout circuit and the sampling fraction of the digitizer.
Here is likely a large difference to Panda. When we compare with Panda we assume our rise time (about 1 ns) and then scale for the area. But that is underestimating the resolution. Because when you have a small SiPM you can have a shorter rise time since you have less capacitance. So even though you operate with less area, this might be made up by the faster readout.

Overall, looking at the Panda results, they essentially have the same resolution for all lengths. Some of them are even worse for shorter bars then for the longer bar with the same width and thickness, but within uncertainties. So my suspicion is that the actual photon distribution only plays a small effect for them.

Best,

Anselm

________________________________________
From: Marco Contalbrigo <mcontalb at fe.infn.it>
Sent: Monday, February 17, 2025 11:52 AM
To: Nilanga Wickramaarachchi, Ph.D. via Clas12_rgh
Cc: Anselm Vossen, Ph.D.
Subject: Re: [Clas12_rgh] [EXTERNAL] RGH meeting February 17

Hi Nilanga,
thank you for this interesting study. You are welcome to
present it next time. Meanwhile, let me ask you some
clarification:

------------------
Slide 2:
------------------

- What do you mean by "pixel": Is it a SiPM ?

- You ask at least 10 photons, and take the time of
the first, is it correct ?

- Do you vary the impact position of the proton or
take just the middle of the bar ?

------------------
Slide 3:
------------------

- Cherenkov radiation is prompt, scintillation is
slow. How can the second arrives earlier ?

------------------
Slide 5:
------------------

- The scale factor describes the fraction of detected
light. I am not sure it drives the resolution. Can not
you consider only the photons within the sensor
equivalent area ?

------------------
Slide 6:
------------------

- What is the difference between coloumn 2 and 3: is
the 2 the first photon, and 3 the threshold time ?

- Which electronics are you considering ?

- In the last two rows, 10 mm is thickness or width ?
Row 4 is better than row 2, and row 5 is better than 3
while I would expect the contrary for wider tiles.

I guess PANDA combines the sensors at both ends, i.e.
has a sort of 1/sqrt(2) improvement.


You may consider also this benchmark:

T.~Rostomyan et al., {\it Timing detectors with SiPM
read-out for the MUSE experiment at PSI},
Nucl. Instrum. Meth. A 986 (2021) 164801.

Ciao, Marco.

On Mon, 17 Feb 2025, Nilanga Wickramaarachchi, Ph.D. via Clas12_rgh wrote:

> Hi All,
>
> I uploaded a few slides on TOF timing resolution studies to the meeting wiki page.
> https://urldefense.com/v3/__https://clasweb.jlab.org/wiki/images/b/b2/RGH_Update_02_17_2025.pdf__;!!OToaGQ!ucw-yfdGe9wQ_SdtxMpMp403tKS9OHa1Q0hKZuTpegRvMMlHQ6piLb-8crTuD2hfwkeaENAwV1Ql7xBNLPzRVBVj$
> I can present it at the next meeting.
>
> Regards,
> Nilanga Wickramaarachchi
>
> ___________________________________________________________________________________________________________________________________________________________________________________________________
> From: Clas12_rgh <clas12_rgh-bounces at jlab.org> on behalf of Marco Contalbrigo via Clas12_rgh <clas12_rgh at jlab.org>
> Sent: Sunday, February 16, 2025 4:11 AM
> To: clas12_rgh at jlab.org <clas12_rgh at jlab.org>
> Subject: [Clas12_rgh] [EXTERNAL] RGH meeting February 17
> Dear all,
> the next RGH meeting is scheduled for Monday
> February 17 at 8:00 am EST (2 pm CET).
>
> We will discuss the recoil status and plans
> for background studies.
>
> Please let me know if you are ready to present a
> contribution and be ready to upload it on the
> wiki:
> https://urldefense.com/v3/__https://clasweb.jlab.org/wiki/index.php/RGH_Meetings__;!!OToaGQ!qMC9F600sjSQKu3j2cz-W7cmU8LVgIqaw8glXNY07ROPiounVSgFCSwLxP0H9OTU5Hm_KK4gX5twu7pQ4UT3_OwhCpW-CPQm$
>
> Zoom connection details:
> ID 160 307 2676
> Code 273174
>
> See you there, Marco.
>
> _______________________________________________
> Clas12_rgh mailing list
> Clas12_rgh at jlab.org
> https://urldefense.com/v3/__https://mailman.jlab.org/mailman/listinfo/clas12_rgh__;!!OToaGQ!qMC9F600sjSQKu3j2cz-W7cmU8LVgIqaw8glXNY07ROPiounVSgFCSwLxP0H9OTU5Hm_KK4gX5twu7pQ4UT3_OwhCr09FFBC$
>
>