?  I don’t think Norman is using a beamspot constraint.  Do you have chisq distributions for Norman’s tracks??

T

> On Mar 24, 2022, at 10:05 AM, Bravo, Cameron B. <[log in to unmask]> wrote:
>
> I have chi2 plots for days. I believe a bias will be introduced if you have the beamspot in the incorrect position in z, and this bias manifests as the asymmetrical z distribution.
>
>
> From: Nelson, Timothy Knight <[log in to unmask]>
> Sent: Thursday, March 24, 2022 10:02 AM
> To: Nelson, Timothy Knight <[log in to unmask]>
> Cc: Graf, Norman A. <[log in to unmask]>; Bravo, Cameron B. <[log in to unmask]>; [log in to unmask] <[log in to unmask]>; hps-software <[log in to unmask]>
> Subject: Re: SVT Vertex Analysis
>
> Also… any idea why the z-vertex distributions are so asymmetric: that seems fundamentally unhealthy.
>
> > On Mar 24, 2022, at 9:59 AM, Timothy K Nelson <[log in to unmask]> wrote:
> >
> > I wonder what the track chisq distributions look like, BTW.
> >
> > Tim
> >
> >> On Mar 24, 2022, at 9:56 AM, Nelson, Timothy Knight <[log in to unmask]> wrote:
> >>
> >> Obviously, there is something going on here that we haven’t thought at all about, but not sure what it is yet.
> >>
> >> However, your study does point out a major issue that should have been obvious and which we didn’t consider the impact of: most of these tracks (and nearly all positrons) don’t hit the first layers because of angular acceptance that begins at something like 30 mrad instead of 15 mrad.  The reason for the positron/electron asymmetry is I believe the acceptance effect that we discovered so long ago: positron tracks in this momentum range have to start out going in the electron direction and vice versa, and angular coverage on the positron side is much better in the front of the detector, relative to the electron side.
> >>
> >> So… it’s a really different (and extremely unusual) set of tracks, acceptance wise, than what we do alignment with.
> >>
> >> Tim
> >>
> >>> On Mar 24, 2022, at 9:29 AM, Graf, Norman A. <[log in to unmask]> wrote:
> >>>
> >>> 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
> >>>
> >>> Use REPLY-ALL to reply to list
> >>> To unsubscribe from the HPS-SOFTWARE list, click the following link:
> >>> https://listserv.slac.stanford.edu/cgi-bin/wa?SUBED1=HPS-SOFTWARE&A=1
> >>>
> >>> Use REPLY-ALL to reply to list
> >>> To unsubscribe from the HPS-SOFTWARE list, click the following link:
> >>> https://listserv.slac.stanford.edu/cgi-bin/wa?SUBED1=HPS-SOFTWARE&A=1
> >>>
> >>> Use REPLY-ALL to reply to list
> >>> To unsubscribe from the HPS-SOFTWARE list, click the following link:
> >>> https://listserv.slac.stanford.edu/cgi-bin/wa?SUBED1=HPS-SOFTWARE&A=1
> >>
> >>
> >> ########################################################################
> >> Use REPLY-ALL to reply to list
> >>
> >> To unsubscribe from the HPS-SOFTWARE list, click the following link:
> >> https://listserv.slac.stanford.edu/cgi-bin/wa?SUBED1=HPS-SOFTWARE&A=1
> >
>