Commissioning and running of sPHENIX

[Anthony Frawley <afrawley AT fsu.edu>]

Hello Stefan,

I am not sure I understand. This table says that a 2 mrad crossing angle means more protons/bunch. I assume that was already factored into the CAD luminosity estimates. So this discussion is just about what effect this has on the polarization?

Thanks

Tony

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From: Sphenix-run-l <sphenix-run-l-bounces AT lists.bnl.gov> on behalf of Stefan Bathe <stefan.bathe AT baruch.cuny.edu>
Sent: Monday, September 18, 2023 3:12 PM
To: sphenix-run-l AT lists.bnl.gov <sphenix-run-l AT lists.bnl.gov>
Subject: Re: [Sphenix-run-l] [request for input] sPHENIX crossing angle with PP in Run24

 

Hi All,

I asked Kiel for some quantitative guidance.  Here’s his answer:

Best,

Stefan

----

Hi Stefan,

Currently I can fill out the table as follows. Obviously 3e11 would be quite high where Run15 and Run22, we had 2.38e11 and 2.25e11 maximum intensities respectively.

crossing angle/mrad | intensity

----------------------------------------

sphenix | STAR         |

----------------------------------------

0            | 0.               | ~2.1e11

0.           | 1                | ~2.6e11

1            | 0                | ~2.6e11

1            | 1                | ~3.0e11

2            | 0                | ~3.0e11

2            | 1                |

2            | 2                |

Kiel

- 

---------------------------------------------------------------------------------
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
----------------------------------------------------------------------------------

On Sep 18, 2023, at 11:07, Yip, Kin <kinyip AT bnl.gov> wrote:

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

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

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