Thank you Kin for the information, interesting … Ming From: Sphenix-run-l <sphenix-run-l-bounces AT lists.bnl.gov> on behalf of Kin Yip <kinyip AT bnl.gov>
Date: Tuesday, September 19, 2023 at 7:35 PM
To: "sphenix-run-l AT lists.bnl.gov" <sphenix-run-l AT lists.bnl.gov>
Subject: [Sphenix-run-l] Wolfram's answer to : "... we might not get back the best performance in 2015 after so many years." From: Fischer, Wolfram <wfischer AT bnl.gov>
Sent: Tuesday, September 19, 2023 9:02 PM
To: Yip, Kin <kinyip AT bnl.gov>; Rosi Reed <rosijreed AT lehigh.edu>
Subject: Re: ... we might not get back the best performance in 2015 after so many years. Hi Kin and Rosi, our performance evolution over many years was built on a model where we run a mode (say full energy Au+Au, or p+p) only 2-3 years apart, during which time we implemented upgrades to remove the next known bottlenecks. With a long gap (order decade), this model may not work anymore. It did not last run. With enough time we should be able to get back to the old performance, with new staff becoming experts again and tuning up all systems to peak performance again. It is unclear if we have enough time for this. Wolfram Dear Wolfram, In Chuyu’s powerpoint ( ![Image removed by sender.]() Crossing angle Lumi reduction.pptx ) related to luminosity and crossing angles, he said “Although It is possible, we might not get back the best performance in 2015 after so many years.” on page 14. You made a similar statement in the RHIC Retreat meeting. Our collaborator asked why curiously (see below). I understand that it’s mostly an observation from the bad performance in the Run 2023, isn’t it ? Will you be able to elaborate a little more ?? Kin Thanks for sharing, this was really interesting. One thing that's not clear to me, when it is said that we aren't able to get the luminosity that we had in previous runs "after so many years", do we really understand the issue? Is it a training issue - I understand that a large fraction of C-AD operators up until Run 23 hadn't been around for top energy running. Is it something in the RHIC ring itself? AGS? Since the luminosity is so important both to the program we can have in sPHENIX and for the EIC, I'd like to understand it a bit better. Hello, Thanks, Chuyu. I’ve updated my https://bnlbox.sdcc.bnl.gov/index.php/s/9oDpcep7ZD5Ciyk , in case some collaborators can’t get to your sharepoint file. Kin
Chuyu Liu
Collider Accelerator Department,
Brookhaven National Lab, Upton, NY
Work: +1 631 344-4431
Cell: +1 631 202-7823
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 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?
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). - ---------------------------------------------------------------------------------
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
---------------------------------------------------------------------------------- Subject: sPHENIX crossing angle with PP in Run24 Date: September 18, 2023 at 09:20:48 EDT * This email originates from a sender outside of CUNY. Verify the sender before replying or clicking on links and attachments. * 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?
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