[Sbs_gems] [EXTERNAL] Fwd: Cosmic data for UV Layer and J1

Fri Nov 5 15:16:54 EDT 2021

Here is the hit distribution for hits on good tracks for the U/V layers from run 11298 (5 uA on LH2, SBS-1 kinematics).

The first plot is for the 2nd U/V layer.

In this plot, the y coordinate extends all the way to 20 cm on the negative side. On the positive side the edge of the active area is cut off by the BigBite magnet acceptance, among other things.

The second plot is the 1st U/V layer.

In this 2nd plot, the y coordinate distribution is cut off on both sides by the magnet acceptance. Since the BigBite GEMs are offset about 3 cm to beam left from the center of the magnet gap, the center of the magnet acceptance is at about -3 cm in the local GEM coordinates.

Some of the “holes” that you see are actually artifacts of the combined effect of using a 4-hit minimum requirement for tracking and the images of dead areas from other layers, some of the “holes” represent dead areas within the layer itself.

But as far as we can tell the active area size is in fact +/- 20 cm horizontally, and that is what we assume in the analysis code.

[cid:image001.png at 01D7D258.26426740]

[cid:image002.png at 01D7D258.26426740]
From: Sbs_gems <sbs_gems-bounces at jlab.org> on behalf of Liyanage, Nilanga K (nl8n) <nl8n at virginia.edu>
Date: Friday, November 5, 2021 at 3:04 PM
To: Jeffas, Sean (sj9ry) <sj9ry at virginia.edu>
Cc: sbs_gems at jlab.org <sbs_gems at jlab.org>
Subject: Re: [Sbs_gems] [EXTERNAL] Fwd: Cosmic data for UV Layer and J1

But I thought the active area goes to +/- 20 cm, right ? why is this edge a few cm inward from there ?

It this what we are seeing in the other UV chambers ?

Best

Nilanga
________________________________
From: Sean Jeffas <sj9ry at virginia.edu>
Sent: Friday, November 5, 2021 3:01 PM
To: Liyanage, Nilanga K (nl8n) <nl8n at virginia.edu>
Cc: Gnanvo, Kondo (kg6cq) <kg6cq at virginia.edu>; sbs_gems at jlab.org <sbs_gems at jlab.org>
Subject: Re: [Sbs_gems] [EXTERNAL] Fwd: Cosmic data for UV Layer and J1

Hi Nilanga,

This is the edge of the active area. The size of the graph is larger than the actual active area. The hits outside of the active area are just noise that got reconstructed improperly. Normally we do not see this with an XY GEM because in that coordinate system even fake hits must fall inside the active area. But if we have a 2D correlation that is not real in the UV GEM then it is possible for that to get reconstructed in an impossible position. This is because of the UV geometry. Hence why only UV GEMs will have noise that shows up outside of the active area.

Best,
Sean

On Fri, Nov 5, 2021 at 2:55 PM Liyanage, Nilanga K (nl8n) <nl8n at virginia.edu<mailto:nl8n at virginia.edu>> wrote:
Hi Sean

Yes, may be the mapping is correct.

But I have a question: What gives rise to the  drop along the sharp straight lines at roughly + and - 160 mm ? Is it the trigger scintillator ?

Best

Nilanga

________________________________
From: Sbs_gems <sbs_gems-bounces at jlab.org<mailto:sbs_gems-bounces at jlab.org>> on behalf of Sean Jeffas <sj9ry at virginia.edu<mailto:sj9ry at virginia.edu>>
Sent: Friday, November 5, 2021 2:15 PM
To: Gnanvo, Kondo (kg6cq) <kg6cq at virginia.edu<mailto:kg6cq at virginia.edu>>
Cc: sbs_gems at jlab.org<mailto:sbs_gems at jlab.org> <sbs_gems at jlab.org<mailto:sbs_gems at jlab.org>>
Subject: Re: [Sbs_gems] [EXTERNAL] Fwd: Cosmic data for UV Layer and J1

Hi All,

Here are the results using 2 hit minimum clusters. I think the UV GEM mapping looks fine. However there are a lot of areas with missing strips adding up (I count at least 7 areas). It looks to be about 5-10% of the active area in missing strips. Since we have time, as Bogdan suggests, I will try to fix as many as I can.

Best,
Sean

On Fri, Nov 5, 2021 at 1:56 PM Gnanvo, Kondo (kg6cq) <kg6cq at virginia.edu<mailto:kg6cq at virginia.edu>> wrote:

Hi Sean,

Maybe you are right, but please double-check carefully without assumption that just because you duplicate the same mapping for the other chambers, that you got all your mapping right.

I see a lot of patterns in both 2D hit map and 1D hit distribution that make me suspect that there is a mapping issue, though I am not prepare to bet my life on this

Best regards

Kondo

From: Sean Jeffas <sj9ry at virginia.edu<mailto:sj9ry at virginia.edu>>
Sent: Friday, November 5, 2021 1:48 PM
To: Gnanvo, Kondo (kg6cq) <kg6cq at virginia.edu<mailto:kg6cq at virginia.edu>>
Cc: Ezekiel Wertz <ewertz at email.wm.edu<mailto:ewertz at email.wm.edu>>; sbs_gems at jlab.org<mailto:sbs_gems at jlab.org>
Subject: Re: [Sbs_gems] [EXTERNAL] Fwd: Cosmic data for UV Layer and J1

Hi Kondo,

The UV layer does not have a mapping problem. It is an exact copy of the mapping from BB, which is proven to be correct. I believe the pattern and all the hits outside the active area are just noisy strips that cause bad 2D correlations, since this is a low level analysis and does not have tracking to check that hits are true. Also notably, I just realized this is an old version that accepts 1 strip clusters, which certainly also contributes a lot to the noise that we see. It may be worth it to rerun with 2 hit minimum clusters.

For the UV data, I see there are some strips missing, and an entire APV on the right most side. I looked at the GEM yesterday and did not see anything disconnected, and also the raw APV data did not show me that the APV was bad. So I am not sure if it is possible to fix all these missing strips. If we have time I can try replacing some APVs, but it will likely end up being more work than it is worth. Also I will note that the large missing area from one APV on the right side correspond to the top of the GEM, and would therefore be outside of the production cross section anyway.

Best,

Sean

On Fri, Nov 5, 2021 at 1:26 PM Gnanvo, Kondo (kg6cq) <kg6cq at virginia.edu<mailto:kg6cq at virginia.edu>> wrote:

Hi Zeke,

I don’t think it is a big deal. Sean or John will probably fix it quickly

Thanks

Kondo

From: Ezekiel Wertz <ewertz at email.wm.edu<mailto:ewertz at email.wm.edu>>
Sent: Friday, November 5, 2021 1:24 PM
To: Gnanvo, Kondo (kg6cq) <kg6cq at virginia.edu<mailto:kg6cq at virginia.edu>>
Cc: sbs_gems at jlab.org<mailto:sbs_gems at jlab.org>
Subject: Re: [Sbs_gems] [EXTERNAL] Fwd: Cosmic data for UV Layer and J1

Hi Kondo,

I am not as familiar with the UV layer mapping. So I'll talk to Sean about this. I'll also do some comparison with the BB UV layer mappings.

Zeke

On Fri, Nov 5, 2021 at 1:19 PM Gnanvo, Kondo (kg6cq) <kg6cq at virginia.edu<mailto:kg6cq at virginia.edu>> wrote:

Hi Zeke,

That is great. Thanks for these first results.

It looks to me that there is a mapping problem with the UV layer.

Please have a look at the pattern of the 2D hit map. Just a minor issue

Best regards

Kondo

From: Sbs_gems <sbs_gems-bounces at jlab.org<mailto:sbs_gems-bounces at jlab.org>> On Behalf Of Ezekiel Wertz
Sent: Friday, November 5, 2021 1:11 PM
To: sbs_gems at jlab.org<mailto:sbs_gems at jlab.org>
Subject: [Sbs_gems] [EXTERNAL] Fwd: Cosmic data for UV Layer and J1

---------- Forwarded message ---------
From: Ezekiel Wertz <ewertz at email.wm.edu<mailto:ewertz at email.wm.edu>>
Date: Fri, Nov 5, 2021 at 11:47 AM
Subject: Cosmic data for UV Layer and J1
To: <sbs_gem at jlab.org<mailto:sbs_gem at jlab.org>>

Hi GEM folks,

Attached you will find cosmic data and plots for the UV layer and J1. Taking cosmic data on the UV layer was priority, but we managed to get INFN J1 running as well. We took this data earlier this week. There were about 500,000 events.

Other than a few strips that look not great, it looks like the UV layer is performing fairly well. Maybe Sean, Anu, or John has more to say about that.

In regards to J1, each module on this layer has 2 shorted sectors. Which we see fairly clearly. However, there is a missing APV on the middle module. This was disabled because of connection problems that have since been better  understood. The top module has a partial or almost missing APV, this connection has since been remedied but needs to be checked. So this APV on the middle module is the last major thing that needs to be resolved for J1. There are some strips on the top and middle module that are partial and it needs to be understood if those are bad strips or partially disconnected APVs.

So again the main result for this is the UV layer. But this is also a good starting place for J1. Also take note that the empty plots are simply because this plotting macro was not adjusted for 2 layers instead of 5.

Best,

Zeke

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