Commissioning and running of sPHENIX

[Alexander Bazilevsky <shura AT bnl.gov>]

    Hi Stefan, 
    
    Ralf has calculations of the expected impact of the cross angle on
    polarization. I haven't seen any calculations like that from STAR
    people. So, they are talking qualitatively (yes, the effect may be
    there), but we are talking quantitatively (the effect is small). 
    I think Ralf may give more details and/or correct my understanding.
    
    
    Sasha.

On 9/18/23 10:09 AM, Stefan Bathe wrote:

      Hi All,

Please see Kiel’s message below.  I don’t feel qualified to answer this by myself.  So I’m asking for input.  But I’d like to turn this around within 24 h.

I think the answer to the question why we are not concerned about running polarized protons with a crossing angle is quantitative:  in principle it’s a concern, but quantitatively we think we can live with it. But I don’t know what the actual evidence is.

I think there’s no reasonable chance we’d switch to a zero crossing angle except in a disaster scenario (luminosity so low that we don’t need a crossing angle; or no tracking).

Best,

Stefan

- 

---------------------------------------------------------------------------------
Stefan Bathe

Professor of Physics
Baruch College, CUNY
and RIKEN Visiting Scientist

Baruch:                                     BNL:
17 Lexington Ave                      Bldg. 510
office 940                                  office 2-229
phone 646-660-6272                phone 631-344-8490
----------------------------------------------------------------------------------

Begin forwarded message:

From: "Hock, Kiel" <khock AT bnl.gov>

Subject: sPHENIX crossing angle with PP in Run24

            Date:
                September 18, 2023 at 09:20:48 EDT
              
            To:
                "stefan.bathe AT baruch.cuny.edu"
                <stefan.bathe AT baruch.cuny.edu>, "Bathe, Stefan"
                <bathe AT bnl.gov>
              
            Cc:
                "Fischer, Wolfram"
                <wfischer AT bnl.gov>, "Minty, Michiko"
                <minty AT bnl.gov>, "Schoefer, Vincent"
                <schoefer AT bnl.gov>, "Gu, Xiaofeng"
                <xgu AT bnl.gov>

* This email originates from a sender outside of CUNY. Verify the sender before replying or clicking on links and attachments. *

                Hi
                  Stefan,
                
                
                To
                  support intensities at RHIC above 2.1e11
                  protons/bunch, a crossing angle at sPHENIX is needed. 
                
                Is
                  there a reason why sPHENIX is not concerned about
                  having a crossing angle for polarized protons where
                  STAR is?
                Is
                  there a possibility that sPHENIX will change to a zero
                  crossing angle during the run, which would limit the
                  maximum intensity?
                
                
                Thank
                  you,
                
                
                
                Kiel
              
            
          
        
        
      
      
      
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-- 
Alexander Bazilevsky
Brookhaven National Laboratory, Bldg. 510D, 2-232
Upton, NY 11973 Tel: 631-344-3712
Email: shura AT bnl.gov
-------------------------------------------------