Commissioning and running of sPHENIX

[Itaru Nakagawa <itaru AT riken.jp>]

Dear Kin,

 Certainly smaller beta* is attractive option though, we know it is the trade off of the backgrounds. I wonder if there was any attempts to operate smaller beta* than 0.85 in the past at 200GeV p+p even for testing. I cannot find any record below.

https://www.agsrhichome.bnl.gov//RHIC/Runs/

 I am kind of surprised if there was any attempt for the small beta* in the past because that's how we usually know the limit. 

In any case the hope is that new collimator around muon arm works to reduce the backgrounds in MVTX even with smaller beta*, right? And we won't know until we actually operate it, right?

Regards,

-itaru

On 2023/12/12 17:15, Perepelitsa, Dennis wrote:

Hi Kin and all,

Thanks a lot for passing this on.

Regarding the beta* = 50cm configuration, do you know if there is a “full” set of more quantitative C-AD projections for what that could look like, i.e. similar to the tables in https://www.rhichome.bnl.gov/RHIC/Runs/RhicProjections.pdf ? 

Dennis

On Dec 12, 2023, at 2:03 PM, Yip, Kin <kinyip AT bnl.gov> wrote:

Hello,

 

Kiel Hock (the RHIC Run Coordinator for 2024) and Guillaume Robert-Demolaize (lattice specialist in C-AD) have been working with beta*=50 cm at IP8 for a month, to the maturity that they think we can use this configuration (for the coming p-p collisions).

 

Compared to the nominal beta*=85 cm,  this will get us higher luminosity in general and also higher % of luminosity within vertex +/- 10 cm.

I include two plots that Kiel has sent me, LumiComp_8550.pdf and CollComp_8550.pdf.

 

The possible downside is that the beta-function in triplets (Q1/2/3) will increase which will generate more scrapping=>backgrounds, giving

rise to more background at IP8.   Angelika Drees (C-AD) – the person who does the collimation --- just confirmed with me about this worry.   She

actually reminded me that on Aug. 1, 2023, we actually tried to increase the beta* to 5 m (500 cm) --- an experiment --- in order to decrease the background.

 

Kiel’s good intention is to try to get us to 75/pb quicker (to achieve our luminosity goal).  I talked with him a few more times today.

The obvious thing to do is to start with beta* = 85 cm first and see what we get, and then try beta* = 50 cm to see how bad the background

is by comparison.

 

Maybe, some of us can discuss this in the Operations Board Meeting this Friday.

 

Below is the email that he sent today and if you can’t see https://www.cadops.bnl.gov/AP/Spin2024/ , I have saved it as PDF:

“RHIC Run-24.pdf”.  ( The important parts should be the beta* and crossing angle. )

 

Kin

 

From: Hock, Kiel <khock AT bnl.gov> 
Sent: Tuesday, December 12, 2023 12:32 PM
To: Lee, Jeong-Hun <jhlee AT bnl.gov>; Yip, Kin <kinyip AT bnl.gov>
Subject: RHIC parameters for Run24

 

Hi Kin and JH,

 

I have the main IR parameters summarized here:https://www.cadops.bnl.gov/AP/Spin2024/ and wanted to confirm them for our lattice designer:

STAR would like to remain at 85 cm and a 0 mrad crossing angle.

sPHENIX would like a smaller beta* (currently shooting for 50 cm) and a 2 mrad crossing angle.

 

Thanks,

 

Kiel

<LumiComp_8550.pdf><CollComp_8550.pdf><RHIC Run-24.pdf>_______________________________________________
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Dennis V. Perepelitsa
Associate Professor, Physics Department
University of Colorado Boulder

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