STAR Flow, Chirality and Vorticity PWG

[Prithwish Tribedy <ptribedy AT rcf.rhic.bnl.gov>]

Hi Niseem,
  Thanks for incorporating my comments. A couple of follow up comments. 
With these included I sign off.

Slide#2:

"S. Gavina"
-->
"S. Gavin"

"M. Abdel-Azizb"
-->
"M. Abdel-Aziz"

In the motivation bullet :
"2-P correlation"
-->
"Two particle (2-P) correlation"

Slide#3:
"Models don't "
-->
"Models do not"


Slide#4:
This statement needs a citation.
"Smaller \eta/s at RHIC"
Or to be more specific you can say something like:
"Smaller \eta/s at RHIC as demonstrated by .... model calcuations"

Slide#5:
"The slope of \sigma_{\Delta \eta} (G_2) is:"
-->
"The slope of \sigma_{\Delta \eta} (G_2) vs multiplicity is:"

I guess the following line is a summary statement and not a conclusion.
"We investigated the  p_T - p_T 2-P correlation function for Au+Auat 200 
GeV and we found that"

Which actually brings my point that somewhere, maybe on this slide you 
should mention what is new from the old STAR paper. For example, you can 
use terms like "we revisit this analysis" and "in a new approcah by 
excluding self correlations"

Slide#8:
I am still not comfortable plotting a_n and v_n on the same slide plot. 
But this is plot from your paper so let's keep it this way. My request 
is to add AMPT on top of this plot or inside the right plot. This is 
just to clarify that the right plot is not obtained using STAR data.

Many notations are undefined on this slide. For example what is v_n^{pT} 
?

"viscus effect"
-->
"viscous effect"

It's not clear what you mean by "viscous effects that has \delta p_T".

Best,
Prithwish




On 2021-07-13 12:01, Niseem wrote:
> Dear Prithwish,
>
> Thanks for the nice point.
>
> Please find the updated slides at,
>
> https://drupal.star.bnl.gov/STAR/node/55552
>
> Thanks,
> Niseem
>
> On 7/12/21 6:46 PM, Prithwish Tribedy wrote:
> > Hello Niseem,
> >   Here are my comments on your slides.
> >
> > Slide#1:
> > "In this analyses"
> > ->
> > "In this analysis"
> >
> > Slide#2:
> > The right figure needs a label -- what is this ? A toy model, cartoon 
> > or simulation ?
> > What is σ_c and σ_0 is not mentioned. You can use the label to clarify 
> > this.
> >
> > 'will be 1"
> > -->
> > "will be unity"
> >
> > "serves to reduce"
> > ->
> > "helps reduce"
> >
> > The Gavin ansatz needs a citation of Gavin's original work.
> >
> > The equations for G_2 shown here as well as the one from your paper 
> > 2101.01555 is different from what was used by ALICE in 1910.14393.
> >
> > Somewhere there is a normalization factor <pT><pT> that is missing in 
> > your equation.
> >
> > For example Eq.2 from ALICE paper:
> > https://urldefense.com/v3/__https://arxiv.org/pdf/1910.14393.pdf__;!!P4SdNyxKAPE!RWsB6eGt9lfCCPAu_EJM_UCalL46hovlXYcXRrmTnzRikQh0fPVEsf1vTmiubhd9N9pdzFkn$ 
> > Is this what you're doing? The G2 definition from ALICE is 
> > dimensionless. If you're using the same definition then there is a 
> > typo on your slide#2,
> >
> > should the pT 2-P correlator be this ?
> >  G2 = 1/<pT><pT> [ <pT pT>/<n><n> - <pT><pT>]
> >
> >
> > slide#3:
> > "Investigations of the pT-pT correlations"
> > -->
> > "Investigations of the pT-pT correlations from STAR"
> >
> > I am a bit confused here by the introduction of two notations f(Δφ) 
> > and G_2(Δφ).
> >
> > What is f(Δφ)? Is it same as G_2(Δφ) that is plotted ?
> >
> > G_2 defined on slide#2 has a dimension of pT^2, doesn't this mean 
> > G_2(Δφ) plotted on slide#3 should also have dimensions of pT^2 ? Did 
> > you miss the units of [GeV/c]^2 on the y-axis of the top left plot ?
> >
> > If f(Δφ) = G(Δφ) then a_n^{pT} is also dimensionful and should have 
> > the units of Gev/c.
> >
> > But then there is the following problem. I see ShinIchi also mentioned 
> > this point in his comments.
> >
> > Your G_2 definition also means a_n^{pT} is not a dimensionless ratio 
> > like v_n. In other words a_n^{pT} doesn't have to be bounded by the 
> > limits of 0 and 1. So, we can't compare a_n^{pT} with v_n.
> >
> > What am I missing ?
> >
> > slide#4:
> > The same argument of dimension goes here. Let's clarify this otherwise 
> > the comparison with ALICE becomes uninterpretable. Did you use the 
> > same definition as ALICE ? But then I don't understand Eq.7 from your 
> > paper 
> > https://urldefense.com/v3/__https://arxiv.org/pdf/2101.01555.pdf__;!!P4SdNyxKAPE!RWsB6eGt9lfCCPAu_EJM_UCalL46hovlXYcXRrmTnzRikQh0fPVEsf1vTmiubhd9N52A-M6d$ 
> > Best,
> > Prithwish
> >
> >
> > On 2021-07-09 15:21, Niseem via Star-fcv-l wrote:
> > > Dear ShinIchi,
> > >
> > > Thanks for the nice point.
> > > I found a scaling factor in my plotting macro for the 70-80. I 
> > > correct
> > > that typo.
> > >
> > > Please find the updated slides at,
> > >
> > > https://drupal.star.bnl.gov/STAR/node/55552
> > >
> > > Thanks,
> > > Niseem
> > >
> > > On 7/9/21 8:08 AM, ShinIchi Esumi via Star-fcv-l wrote:
> > >
> > > > Dear Niseem
> > > > Thanks for the answers, I'll wait for your next pwg presentation.
> > > > The error bars that we see on the correlation functions (G2 plot),
> > > > which is only visible
> > > > for peripheral in both delta_phi (on page 3) and delta_eta (on page
> > > > 4), do look strange
> > > > to me, if this is meant for statistical error, just because of the
> > > > point-to-point “statistical”
> > > > fluctuations between neighboring data points are much smaller than
> > > > the error bars.
> > > > Since you do not have any specific pT selection (0.2 - 2.0 GeV/c),
> > > > so that the statistical
> > > > errors should not be visible anyway even in peripheral, isn’t it?
> > > > Or are they systematic
> > > > error, in stead?
> > > >
> > > > Best regards, ShinIchi
> > > >
> > > > On Jul 9, 2021, at 5:42, Niseem via Star-fcv-l
> > > > <star-fcv-l AT lists.bnl.gov> wrote:
> > > >
> > > > Hi ShinIchi,
> > > >
> > > > Thanks for your nice comments, please find the updated slides at the
> > > > same link,
> > > >
> > > > https://drupal.star.bnl.gov/STAR/node/55552
> > > >
> > > > For your comments,
> > > > It could be informative, if you could plot "v2,3,4 vs centrality”
> > > > on top of the plot “a2,3,4 vs centrality” at the bottom-left of
> > > > page 3 with some scaling constant (better to be common for all the
> > > > orders) in order to show the centrality dependent shape (which does
> > > > not have to be in the talk, maybe in the analysis note later).
> > > > > > I added a plot to the backup slide showing the v_n and the
> > > > a^{p_T}_n.  I will include this in our analysis note later.
> > > >
> > > > The top-left formula of page 3 does include offset parameter a0^pT,
> > > > which also seems to show a possibly interesting centrality
> > > > dependence, that you could consider showing (maybe in the analysis
> > > > note...)
> > > > > > I showed this before in the PWG meeting. I will include this in
> > > > the analysis note which I’m working on it now.
> > > >
> > > > I was still thinking about the point I raised yesterday in the PWG
> > > > related to above points, how we can define the an^pT parameter to be
> > > > able to compare this with vn. Since G2 is defined as pT square after
> > > > subtracting the baseline that is the average pT square, so that the
> > > > a0^pT parameter is a kind of measure of "non-flow" with a dimension
> > > > of (GeV/c)^2 and an^pT parameters are the measure of "flow" with a
> > > > dimension of (GeV/c).
> > > >
> > > > G2’ = G2 / baseline = (pT_correlation - baseline) / baseline
> > > >
> > > > If we think about using modified G2’ as above in stead of your
> > > > current G2, one can plot (1) an^pT/<pT>, which is more comparable
> > > > definition to the "non-flow subtracted vn”, and/or (2)
> > > > an^pT/sqrt(baseline + a0^pT), where the baseline is the average pT
> > > > square, this is could even be more reasonable to be compared with vn
> > > > measurement.
> > > > In this definition, (1)"non-flow subtracted vn" is even larger the
> > > > other one (2), which is similar to the difference between reference
> > > > fitting (or c1_subtraction) and template fittings for the small
> > > > system vn analysis.
> > > > > > I will discuss this point with Claude Pruneau and I will update
> > > > the PWG.
> > > >
> > > > How is sigma_delta_eta(G2) defined? Is this defined as RMS or
> > > > Gaussian fitting of G2(delta_eta) distribution? How did you treat
> > > > the baseline that we see in G2 as a function of delta_eta? I
> > > > remember we’ve discussed this sometime ago in the PWG, but not
> > > > yesterday. The baseline could also be defined from a0^pT parameter
> > > > from azimuthal fitting at large delta_eta or even in 2D... The sigma
> > > > (or RMS) would largely be affected by the method how we define the
> > > > baseline, so we need to make sure what we do and what we observe.
> > > > > > (1)  sigma_delta_eta(G2) = RMS, I added this to the slides
> > > > > > (2) The baseline is defined from the from azimuthal fitting at
> > > > different delta_eta
> > > > > > (3) The baseline decrease with increasing the Nch (i.e. it will
> > > > not impact the linear increase of the  RMS with Nch)
> > > > > > (4) Now I’m working with the SBU and WSU groups on a paper
> > > > proposal and we will include all this information in our analysis
> > > > note
> > > >
> > > > Related to this, several different cuts on delta_phi to look at
> > > > delta_eta shape, as well as, several different cuts on delta_eta to
> > > > look at delta_phi shape, would be important, 2D analysis could even
> > > > be better as we discussed at the end of PWG yesterday.
> > > > > > Now I’m working with the SBU and WSU groups on a paper proposal
> > > > and we will include all this information in our analysis note.
> > > >
> > > > Thanks,
> > > > Niseem
> > > >
> > > > On 7/8/21 2:12 AM, ShinIchi Esumi via Star-fcv-l wrote:
> > > >
> > > > Dear Niseem
> > > >
> > > > It could be informative, if you could plot "v2,3,4 vs centrality”
> > > > on top of the
> > > > plot ”a2,3,4 vs centrality” at the bottom-left of page 3 with
> > > > some scaling
> > > > constant (better to be common for all the orders) in order to show
> > > > the
> > > > centrality dependent shape (which does not have to be in the talk,
> > > > maybe
> > > > in the analysis note later).
> > > >
> > > > The top-left formula of page 3 does include offset parameter a0^pT,
> > > > which
> > > > also seems to show a possibly interesting centrality dependence,
> > > > that you
> > > > could consider showing (maybe in the analysis note...)
> > > >
> > > > I was still thinking about the point I raised yesterday in the PWG
> > > > related to
> > > > above points, how we can define the an^pT parameter to be able to
> > > > compare
> > > > this with vn. Since G2 is defined as pT square after subtracting the
> > > > baseline
> > > > that is the average pT square, so that the a0^pT parameter is a kind
> > > > of
> > > > measure of "non-flow" with a dimension of (GeV/c)^2 and an^pT
> > > > parameters
> > > > are the measure of "flow" with a dimension of (GeV/c).
> > > >
> > > > G2’ = G2 / baseline
> > > > = (pT_correlation - baseline) / baseline
> > > >
> > > > If we think about using modified G2’ as above in stead of your
> > > > current G2, one can plot
> > > > (1) an^pT/<pT>, which is more comparable definition to the "non-flow
> > > > subtracted vn”,
> > > > and/or (2) an^pT/sqrt(baseline + a0^pT), where the baseline is the
> > > > average pT square,
> > > > this is could even be more reasonable to be compared with vn
> > > > measurement.
> > > > In this definition, (1)"non-flow subtracted vn" is even larger the
> > > > other one (2),
> > > > which is similar to the difference between reference fitting(or
> > > > c1_subtraction) and
> > > > template fittings for the small system vn analysis.
> > > >
> > > > How is sigma_delta_eta(G2) defined? Is this defined as RMS or
> > > > Gaussian fitting
> > > > of G2(delta_eta) distribution ? How did you treat the baseline that
> > > > we see in G2 as
> > > > a function of delta_eta? I remember we’ve discussed this sometime
> > > > ago in the PWG,
> > > > but not yesterday. The baseline could also be defined from a0^pT
> > > > parameter from
> > > > azimuthal fitting at large delta_eta or even in 2D... The sigma (or
> > > > RMS) would largely
> > > > be affected by the method how we define the baseline, so we need to
> > > > make sure
> > > > what we do and what we observe.
> > > >
> > > > Related to this, several different cuts on delta_phi to look at
> > > > delta_eta shape, as well
> > > > as, several different cuts on delta_eta to look at delta_phi shape,
> > > > would be important,
> > > > 2D analysis could even be better as we discussed at the end of PWG
> > > > yesterday.
> > > >
> > > > Best regards, ShinIchi
> > > >
> > > > On Jul 8, 2021, at 4:41, webmaster--- via Star-fcv-l
> > > > <star-fcv-l AT lists.bnl.gov> wrote:
> > > >
> > > > Dear star-fcv-l AT lists.bnl.gov members,
> > > >
> > > > Niseem Magdy Abdelwahab Abdelrahman (niseemmagdy AT yahoo.com) has
> > > > submitted a
> > > > material for a review, please have a look:
> > > > https://drupal.star.bnl.gov/STAR/node/55552
> > > >
> > > > ---
> > > > If you have any problems with the review process, please contact
> > > > webmaster AT www.star.bnl.gov
> > > > _______________________________________________
> > > > Star-fcv-l mailing list
> > > > Star-fcv-l AT lists.bnl.gov
> > > > https://lists.bnl.gov/mailman/listinfo/star-fcv-l
> > > >
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