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Hi Norman, 

I agree we probably want to find the large sensor displacement and fix it, which is causing the momentum structure we see. I have been staring at that momentum structure for weeks now. The bump used to be lower, underneath all the lower momentum electrons and I got it to move up some. I am pretty sure these are FEEs that have both slot and hole side hits, we could probably look at plots and chat about why I think this for at least an hour. I agree we still want to fix this major issue before we seriously go down the path of aligning the beam spot. Every time I have fixed something similar to this issue, the besmspot moves and I have to massage it back anyway. You might recall from slack a few hours after my talk I showed the top electron momentum with a really low momentum cut. I think the extra structure we saw there (double "bump" around 1GeV) is a related effect of the same issue. It is possible one of these three new detectors has improved the situation some, but I don't think all the way yet. I believe the issue is in the top layer 5 slot region of the SVT. It is tricky to align it though because it is a small fraction of FEEs that go over there, and they depend on the alignment of the slot side wrt the hole side. Need to find a selection which enriches the sample with these. 

Your later suggestions for how to align are rather vague and unhelpful. I wish it was possible to chat with you outside of meetings and email. Coordinating our efforts more often than just at a couple meetings per week where we don't have much time and a lot of other stuff to talk about would probably lead to more efficient progress.

Cheers,
Cameron


From: Graf, Norman A. <[log in to unmask]>
Sent: Thursday, March 24, 2022 9:29 AM
To: Bravo, Cameron B. <[log in to unmask]>; Graf, Norman A. <[log in to unmask]>; [log in to unmask] <[log in to unmask]>; hps-software <[log in to unmask]>
Subject: RE: SVT Vertex Analysis
 

Hi Cameron,

 

Thanks for taking a look at this presentation. I’ll take a look at the new detectors and post my findings.

 

It would be very useful if you would run the alignment over runs 753 and 754 using the wire positions as beamspot constraints, viz.

 

01753 SVT beamspot at (0.0, 0.2, 34.544)

01754 SVT beamspot at (0.0, 0.2, 20.600)

 

You can either accept all good electron and positron tracks and fit without a momentum constraint or you can align using only FEEs and impose the momentum constraint, but take note of the structure in the top electron momentum spectrum shown on slide 3. I believe that originates from FEEs on the positron side, so a first pass alignment without a momentum constraint might be needed there.

 

Thanks,

Norman

 

From: [log in to unmask] <[log in to unmask]> On Behalf Of Bravo, Cameron B.
Sent: Wednesday, March 23, 2022 11:53 PM
To: Graf, Norman A. <[log in to unmask]>; [log in to unmask]; hps-software <[log in to unmask]>
Subject: Re: SVT Vertex Analysis

 

Dear Norman,

 

Thanks for the plots, these are interesting to me. I have added 3 detectors to the ali21 branch of hps-java.

I would love to see all these plots for all three of those detectors.

 

Thanks,

Cameron

From: [log in to unmask] <[log in to unmask]> on behalf of Graf, Norman A. <[log in to unmask]>
Sent: Wednesday, March 23, 2022 10:46 PM
To: [log in to unmask] <[log in to unmask]>; hps-software <[log in to unmask]>
Subject: SVT Vertex Analysis

 

Dear Colleagues,

 

As a follow-up to my analysis of FEE events which I presented at this morning’s analysis/recon meeting (https://confluence.slac.stanford.edu/pages/viewpage.action?pageId=341254335&preview=/341254335/341256282/20220322_CalibrationReconstruction_Graf_HPS_DAWG_Meeting.pdf) I have reconstructed the data that was taken using the SVT positioning wires as targets. The positions of these wires are known to much higher precision than that of the tungsten target, and using both positron and electron tracks in the data should reduce the systematics and improve the precision of the vertex measurement. I have posted a new set of slides summarizing the current state of this analysis to https://confluence.slac.stanford.edu/pages/viewpage.action?pageId=341254335&preview=/341254335/341257564/20220323_SVTWireTargetVertexAnalysis_Graf_HPS_Weekly_Meeting.pdf . There are a number of interesting features in the data but the most interesting feature for me is that the latest SVT geometry encapsulated in the HPS_Run2021Pass2FEE detector reconstructs the wire positions almost a centimeter downstream of their measured locations. I invite you to look at the slides and let me know if you have any questions or suggestions on how to improve this analysis.

 

Sincerely,

Norman

 

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