sPHENIX cold QCD topical group

[Jamie Nagle <jamie.nagle AT colorado.edu>]

Hello Itaru,

Apologies if I was not clear in the  email.    The ZDCs will stay in their current position for now.    When we know how the TPC is working and if we will switch to +1.5 or +2.0 mrad, we will re-visit the issue of the ZDC positions.

Sincerely,

Jamie

||------------------------------------------------------------------------------------------
|| James L. Nagle   
|| Professor of Physics, University of Colorado Boulder

|| EMAIL:   jamie.nagle AT colorado.edu
|| SKYPE:  jamie-nagle        
|| WEB:      http://spot.colorado.edu/~naglej 
||------------------------------------------------------------------------------------------

On Wed, Jul 17, 2024 at 8:58 AM Itaru Nakagawa <itaru AT riken.jp> wrote:

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Hi Jamie,

 Do you meant we don't change the ZDC location for the rest of the p+p run? It is true that there is a mechanism that polarization vector has to be vertical in order to prevent the depolarization in store, therefore the vector suppose to be vertical. However please be aware that we are trying to observe the asymmetries in the level of 1% or even smaller. I am not sure if we can blindly believe the polarization vector wouldn't be the issue for the systematic error of our measurement with the measurement of the current ZDC position. We haven't seen anything obviously wrong in the observed asymmetries yet except for +2mrad data though, we are not yet reaching to the level to evaluate the precision of 1%. We are waiting for cross check analysis results now.

Regards,

-itaru

On 2024/07/16 5:28, Jamie Nagle wrote:

Hello  ZDC peoples (cc cold QCD),

After getting multiple inputs / viewpoints, I have decided that we will not move the ZDCs from their current positions.     We need our focus of experts to be in many other areas (including  TPC isobutane, etc), and leaving our luminosity counters as they are is a simplifying effort.

I know there may  be some concerns if the polarization is not vertical, but there are many reasons to believe this is not the case --  and likely not possible.     However, since we had a situation where the EMCal was unavailable last night, I instructed the shift crew to take a set of ZDCNS triggered runs.     It would be great if people can check these high statistics runs for vertical polarization and report at one of the upcoming SCM.

Run 48445, 48446, 48447.

Sincerely,

Jamie

||------------------------------------------------------------------------------------------
|| James L. Nagle   
|| Professor of Physics, University of Colorado Boulder

|| EMAIL:   jamie.nagle AT colorado.edu
|| SKYPE:  jamie-nagle        
|| WEB:      http://spot.colorado.edu/~naglej 
||------------------------------------------------------------------------------------------