Sphenix-calibration-l mailing list

["Frantz, Justin" <frantz AT ohio.edu>]

Hi all,

The discussion so far I think is leading to another question:  Suppose we did 
SOME p+p running in the first year to address our concerns.  How much do we 
need?  Can we do anything on the JES without something like 100 /pb?  Or does 
it help "enough" to have maybe 30/pb, and then still assume we would sharpen 
up the uncertainties after the 2nd years long pp running before releasing 
final results?     I actually think John Haggerty's plan has always been to 
commission with p+p, Jamie's slides don't specify what the commissioning 
would be done with, but I thought maybe Christof was saying  at our mtg there 
was some concern raised somewhere about the 2 weeks lost to switch the 
magnets (hence my d+d suggestion), which is the only argument I've heard 
against doing commissioning with p+p.    Could Spencer or Takao you clarify 
what politics would be preventing p+p in the first year, and does this apply 
to a smaller commissioning run?  

I am fine with the statement Takao wrote, were you planning  to send that 
tonight?   I can't imagine why we wouldn't also bring up all the concerns it 
says in there at tomorrow's meeting, I would be planning to if no one else 
is.  Will others be called into that tomorrow?  

Finally for Aaron specifically, if the problem is indeed the magnets and the 
two weeks lost, is my idea of d+d too crazy for you to comment on?  I don't 
believe for a second that the UE at 200 GeV from this would lead to virtually 
any modifications to the JES compared to p+p, the multiplicity is too low-- 
even in the most central collisions, but I don't know about some kind of 
model dependence or isospin effects that might play a role.

-Justin

----------------------------------------------
Justin Frantz, Ph. D.  
RHIC/AGS User Executive Committee
Brookhaven National Lab
Associate Professor
Ohio University Dept. Of Physics and Astronomy   
frantz AT ohio.edu   
646-228-2539  
PERSONAL ZOOM MEETING:  369-910-7530   Password:  1

> -----Original Message-----
> From: Aaron Angerami [mailto:angerami AT cern.ch]
> Sent: Thursday, August 13, 2020 2:50 PM
> To: Frantz, Justin
> Cc: Christof E Roland; Christof Roland via sPHENIX-calibration-l; Megan
> Connors; Takao Sakaguchi
> Subject: Re: BUR input from Calibration TF
> 
> Hi,
> 
> I think Takao’s draft input sent to the whole calibration TF list pretty 
> well
> summarizes my point of view.
> 
> What I didn’t see in Jamie’s draft slides was the motivation for taking 
> Au+Au
> in year 1 (2023) and only Au+Au. Does anyone know either a physics/political
> reason or RHIC technical constraint of why this needs to be? Is this an item
> that is even open for discussion?
> 
> In the current plan we have 11.5 weeks of commissioning + 9 weeks of
> physics data taking w/ Au+Au in 2023. What do we plan to achieve with that
> data, specifically what measurements do we plan to perform? I don’t see
> how we can establish a jet energy scale without pp data— this may be
> possible but no one has come up with an idea on how to do it. So this would
> mean that either
> 
> -We use the 2023 Au+Au data, but cannot publish any measurements using
> fully reconstructed jets until after we have taken the pp data in 2024 (and
> had time to analyze it).
> 
> -We do jet measurements using the 2023 data with no control over the
> energy scale, not because its particularly valuable to the field, but 
> because its
> the only thing we can do. As I tried to say in the meeting, I think this is 
> not a
> good idea. I also see a scenario in which people generally agree this is a 
> bad
> idea, but that goes out the window when the data actually comes or a major
> conference is on the horizon.
> 
> A good example is something like a jet R_CP. It is true that if you do this
> properly, a large component of the JES uncertainty (and also the JER) is
> correlated between central and peripheral collisions, and will partially 
> cancel
> in the ratio. However, the cancelation is not exact and properly evaluating 
> it
> requires knowledge of the absolute JES uncertainty. For example, in
> measurements at the LHC, even though there is cancellation, this is still 
> the
> largest source of systematic uncertainty. It’s probably fine to show a 
> result at
> a conference with these caveats, but I think it would be poor form to
> compare directly to a theory calculation or other experimental data.
> 
> So to try to answer Justin’s question, I think taking only Au+Au data in 
> 2023
> could “work” if there are some protocols of how the data is interpreted for
> cases like this would be established and enforced by the spokespersons, and
> I think the calibration TF has a role in helping craft those protocols. 
> This has to
> be a pretty common issues in experiments with the how people use data
> taken during commissioning. The Au+Au data of course will be real physics
> data, but some of those basic ideas should still apply.
> 
> Best,
> Aaron
> 
> 
> 
> 
> > On Aug 13, 2020, at 9:58 AM, Frantz, Justin <frantz AT ohio.edu> wrote:
> >
> > Hi guys,  I would be willing to write it up.   Perhaps though it's 
> > easiest to just
> attend Jamie's open meeting tomorrow on this (I was planning to) and
> express it there--- if we can come to a bit more of  a conclusion about it.
> >
> > Cause I think I knew where the general conclusion was headed but we did
> table the discussion before we had quite reached the end.   Perhaps we
> could just by email see if we can just make some statements concerning our
> areas that would form the basis of such a response, then I can try to
> integrate them essentially, and already bring up whatever fraction is
> appropriate by tomorrow's meeting.
> >
> > I had a couple questions though based on the discussion we did have:  
> > First
> for Aaron, if I understood your point of view, you do think it could work 
> for
> the JETS to get the p+p calibration data 0.75yr to 1 yr  afterwards,  ie and
> essentially finalize calibration after the fact, but you are more concerned 
> with
> the pressure to come up with first results before that (like R_CP), managing
> expectations (more internal or external?)?
> >
> > Here's a crazier idea:  what about commissioning with deuteron+deuteron
> or if there is another small system that has a more similar e/m  so that the
> magnet's don't need moved or as far?   (this was the original motivation in 
> my
> understanding why Rhic did d+Au in the first decade rather than p+Au.)  If
> this is at all a possibility I assume d+d would be virtually be the same as 
> p+p
> even for jets UE event etc (OK there's a little difference).  Is something 
> as
> large as d+Au still "OK" ie quite better than peripheral AuAu?   How big 
> could
> it go if this would work?
> >
> >
> > ----------------------------------------------
> > Justin Frantz, Ph. D.
> > RHIC/AGS User Executive Committee
> > Brookhaven National Lab
> > Associate Professor
> > Ohio University Dept. Of Physics and Astronomy
> > frantz AT ohio.edu
> > 646-228-2539
> > PERSONAL ZOOM MEETING:  369-910-7530   Password:  1
> >
> >
> >> -----Original Message-----
> >> From: Christof E Roland [mailto:cer AT mit.edu]
> >> Sent: Thursday, August 13, 2020 4:30 AM
> >> To: Christof Roland via sPHENIX-calibration-l
> >> Cc: Frantz, Justin; Megan Connors; Aaron Angerami; Takao Sakaguchi
> >> Subject: BUR input from Calibration TF
> >>
> >> Hi Everybody,
> >>
> >> in the last TF meeting we mentioned writing a few lines as input to the
> next
> >> BUR meeting on Friday.
> >> Would anybody voluteer to prepare a draft?
> >>
> >> Thanks
> >>
> >>   Takao & Christof