Sphenix-calibration-l mailing list

[Takao Sakaguchi <takao AT bnl.gov>]

Dear Justin, Aaron, and all,

 Thanks for your input and comments. I also appreciate for comments
from Spencer. There is one reason to send it off tomorrow morning,
which is to get feedback from people residing in Europe. I would like to
hear from them and then send it to BUR TF.

 I remember that Jamie mentioned reasoning of pushing Au+Au for
the first year running rather than p+p, which relates to STAR's
run proposal. This is the political reason I remember. A good operational
argument from Christof was that if we run long-enough p+p collisions
in the year-1, we have to take that data perfectly, since we won't be
able to request another. I personally prefer to have "some" p+p data
(or d+d as Justin proposed if it is easier) in the year-1. With that we
could get data for calibration and basis for A+A analysis. By the way,
the isospin effect in jet production is negligible, and the effect in
photon production is kind of well understood, I think.

 The draft was trying to state that p+p is essential to establish initial
calibration and to perform precision measurement in Au+Au. It may
not be reflected in the BUR of this year, but I believe that it is important
to make our stance clear whenever this kind of discussion comes up.
The calibration TF is in very important position in this regard.

 I encourage those who can make the BUR meeting to join that.

Best,
Takao

On 8/13/20 8:15 PM, Frantz, Justin wrote:
> 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