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sphenix-run-l - Re: [Sphenix-run-l] Fwd: [request for input] sPHENIX crossing angle with PP in Run24

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Subject: Commissioning and running of sPHENIX

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Chronological Thread  
  • From: "Yip, Kin" <kinyip AT bnl.gov>
  • To: Anthony Frawley <afrawley AT fsu.edu>, "Bazilevsky, Alexander" <shura AT bnl.gov>, "sphenix-run-l AT lists.bnl.gov" <sphenix-run-l AT lists.bnl.gov>
  • Cc: "Liu, Chuyu" <cliu1 AT bnl.gov>
  • Subject: Re: [Sphenix-run-l] Fwd: [request for input] sPHENIX crossing angle with PP in Run24
  • Date: Mon, 18 Sep 2023 15:07:34 +0000

Hi,

 

Our polarization experts such as Ralf Seidl and Sasha have had some email discussion about the polarization effect with crossing angles.

 

  • What is at stake here? Do we have guidance from CAD on crossing angle vs maximum luminosity?

 

In the RHIC Retreat, basically, C-AD (Chuyu Liu and Wolfram Fischer) told us that what we saw ( a factor of 6-7) is “right” and real.

Their previous calculation assuming Gaussian only profile is wrong.  After the RHIC Retreat, I asked Chuyu and he

sent us this file for his new calculation :

 

https://bnlbox.sdcc.bnl.gov/index.php/s/9oDpcep7ZD5Ciyk

 

Kin

 

From: Sphenix-run-l <sphenix-run-l-bounces AT lists.bnl.gov> On Behalf Of Anthony Frawley
Sent: Monday, September 18, 2023 10:41 AM
To: Bazilevsky, Alexander <shura AT bnl.gov>; sphenix-run-l AT lists.bnl.gov
Subject: Re: [Sphenix-run-l] Fwd: [request for input] sPHENIX crossing angle with PP in Run24

 

Hello Stefan,

 

This seems like a very important question that we should make sure to get right.

 

What is at stake here? Do we have guidance from CAD on crossing angle vs maximum luminosity?

 

Thanks

Tony

 


From: Sphenix-run-l <sphenix-run-l-bounces AT lists.bnl.gov> on behalf of Alexander Bazilevsky <shura AT bnl.gov>
Sent: Monday, September 18, 2023 10:21 AM
To: sphenix-run-l AT lists.bnl.gov <sphenix-run-l AT lists.bnl.gov>
Subject: Re: [Sphenix-run-l] Fwd: [request for input] sPHENIX crossing angle with PP in Run24

 

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

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
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