Commissioning and running of sPHENIX

[David Morrison <morrison AT bnl.gov>]

Hi Stefan,

It is also incorrect for Kiel to ask "why sPHENIX is not concerned".  We are concerned about *everything* that affects the science output of sPHENIX.  This includes a concern about the effect of space charge in the TPC. 

Dave

On 9/18/23 10:21 AM, Alexander Bazilevsky wrote:

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

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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
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Email: shura AT bnl.gov
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-- 
David Morrison  Brookhaven National Laboratory  phone: 631-344-5840
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