STAR Flow, Chirality and Vorticity PWG

["Wang, Fuqiang" <fqwang AT purdue.edu>]

Jagbir,

Please see my replies below.

Best regards,
Fuqiang



> -----Original Message-----
> From: jagbir <jagbir AT rcf.rhic.bnl.gov>
> Sent: Monday, December 14, 2020 11:18 AM
> To: Wang, Fuqiang <fqwang AT purdue.edu>
> Cc: STAR Flow, Chirality and Vorticity PWG <star-fcv-l AT lists.bnl.gov>; 
> star-cme-
> focusgroup-l AT lists.bnl.gov; aggarwal AT pu.ac.in
> Subject: Re: [Star-fcv-l] FCV PWG meeting, 18/Nov/2020 (Wed) 9:30am (New
> York time zone)
> 
> Dear Fuqiang,
> 
>     Please find my replies below:-
> 
> 1.   I understand your motivation doing that but I don't agree this is
> the right approach
>     (I think it causes biases).
> 
>     Please let me know why this is not the right approach and what kind of 
> biases
> you meant.
[Fuqiang Wang] because your selection is predominated by statistical 
fluctuations yet you're applying a cut on those statistical fluctuations.

Can you plot (data-chrgR. Bkg) and (Correlated bkg) vs (Dbmax bin) on slide 
25 so we can see the details better?

> 
> 
> 2.   you have only one point left. Your f_cme is basically the
>       (Delta gamma of those events in that Dbmax bin)
>       - (Delta gamma of a random collection of events in the same 
> centrality bin
> which happen
>       to have the same Dbmax_shuffle bin)
>       - (Delta gamma of those same random events calculated after the 
> charges
> are shuffled)
>       Do I understand it correctly?
> 
>     If only one point is left as you wrote, please see the explanation
> below:
> 
>     Here, there is nothing like random collection of events in the same 
> centrality bin.
[Fuqiang Wang] I mean the max Dbmax_shuffle bin is a random collection of 
events from this centrality bin.

>     We select events depending on Db+-max i.e., depending on the 
> back-to-back
> charge
>     separation fDbCS = Db+-max-1. As you wrote only one point, in that case 
> it is
> the
>     top 10% Db+-max events corresponding to maximum back-to-back charge
> separation events.
>     It is similar to selecting events in particular collision centrality 
> depending on
>     the impact parameter or event multiplicity. As we have selected in the 
> data
> top 10%
>     Db+-max corresponding to maximum back-to-back charge separation events,
> in  same way
>     we select events from charge reshuffle in the same collision centrality 
> for top
> 10%
>     Db+-max(here Db+-max of charge reshuffle) corresponding to maximum back-
> to-back
>     separation. Now we get delta_gamma_data of real data events
> corresponding to top
>     10% Db+-max of data and delta_gamma_sta of charge reshuffle events
> corresponding to top
>     10% Db+-max of charge reshuffle for a given collision centrality which 
> gives
>     us delta_gamma due to statistical fluctuations. Now for correlated
> background we
>     look for real events in the data corresponding to the top 10% Db+-max
>   of charge
>     reshuffle in a given centrality and get delta_gamma_cor from those real
>     data events.
> 
>     Now the f_CME is obtained as
> 
>     f_CME = N1*(delta_gamma_data - delta_gamma_sta -
> delta_gamma_cor)/(delta_gamma_data * N)
> 
>     Where N1 is number of events in top 10% Db+-max and
>     N is total number of events in a given collision centrality.
> 
> Thank you,
> With regards,
> Jagbir Singh
> 
> On 2020-12-14 10:32, Wang, Fuqiang wrote:
> > Jagbir,
> >
> > Thanks for your answers.
> >
> > To your questions:
> >> Please clarify the following
> >>       Of course you've also removed the large charge-shuffle
> >> background which is basically
> >>       an autocorrelation effect (sort to speak) due to the Dbmax (and
> >> Dbmax_shuffle)
> >>       selection bias.
> > I was just saying it in passing, referring to the fact that you're
> > largely selecting on statistical fluctuations and trying to remove the
> > auto-correlation effect by shuffling. It wasn't a question.
> >
> >>       Please explain the following:
> >>       So is your finite signal really due to the difference between
> >> the average of ratios
> >>       and the ratio of averages (or perhaps also due to residual
> >> effect from shuffling)?
> > I was referring to the fact that if you had a single Dbmax bin (i.e.
> > taking average first and then ratio) then you'd get zero signal by
> > definition. You now have 10 bins and take ratios first in each bin and
> > then take average of the ratios, and get a positive signal. During the
> > focus meeting discussion, it was made clear that your analysis
> > required multiple Dbmax bins, not taking average of all bins, but only
> > those with Delta gamma > 0. So now I think I understand technically
> > how you did it. I understand your motivation doing that but I don't
> > agree this is the right approach (I think it causes biases).
> > So let me try to understand better:
> > On slide 9 of your focus meeting presentation
> > https://drupal.star.bnl.gov/STAR/system/files/CME_FOCUS.pdf, you
> > state:
> > (1) If Delta gamma_bkg. is negative then it is taken as zero.
> > (2) If gamma_SS is not negative and gamma_OS is not positive then
> > delta gamma = 0.
> > Now to slide 25, let's take one centrality say 40-50%, you have the
> > blue points (signal) and red+green points (bkg). The 8 points to the
> > right of this centrality: all of them have negative bkg and negative
> > Delta gamma, so they are not counted in your calculation of CME
> > fraction. Now you're left with the two leftmost points. Do both points
> > satisfy (2) above? I know both points seem to have bkg>0 & Delta
> > gamma>0 but it's unclear if they satisfy SS<0 & OS>0. Assume they do,
> > then you're taking average of these two data points. For the sake of
> > simplicity, let me say you have only one point left. Your f_cme is
> > basically the (Delta gamma of those events in that Dbmax bin)
> > - (Delta gamma of a random collection of events in the same centrality
> > bin which happen to have the same Dbmax_shuffle bin)
> > - (Delta gamma of those same random events calculated after the
> > charges are shuffled) Do I understand it correctly?
> >
> > Best regards,
> > Fuqiang
> >
> >
> >
> >> -----Original Message-----
> >> From: jagbir <jagbir AT rcf.rhic.bnl.gov>
> >> Sent: Sunday, December 13, 2020 10:12 AM
> >> To: Wang, Fuqiang <fqwang AT purdue.edu>
> >> Cc: STAR Flow, Chirality and Vorticity PWG
> >> <star-fcv-l AT lists.bnl.gov>;
> >> star-cme-
> >> focusgroup-l AT lists.bnl.gov; aggarwal AT pu.ac.in
> >> Subject: Re: [Star-fcv-l] FCV PWG meeting, 18/Nov/2020 (Wed) 9:30am
> >> (New York time zone)
> >>
> >> Dear Fuqiang, all,
> >>
> >>    Sorry for not answering your email. Infact, I did not look this
> >>    email. Please go through my replies below:
> >> ------------------------
> >>
> >>   1. A few events do not satisfy this cut so not including in it
> >> Db+-max
> >>      but in overall calculations all events are included.
> >>
> >>   2. Yes
> >>
> >>   3. We reshuffle charges in each event. We donot randomize charges
> >>      according to the positive/negative charge ratio of the given
> >> event.
> >>      In fact, we pick up one event and reshuffle positive/negative
> >> charges
> >>      keeping theta,  phi, number of postive charges and number of
> >> negative
> >>      charges as such. After this we calculate gamma correlator. This
> >> procedure
> >>      is repeated for each event. The Db+-max of reshuffle  is a bit
> >> bit wider
> >>      than the  real distribution which may be due to some
> >> correlations in the
> >>      real data whereas reshuffle is purely randomize. Db+-max binning
> >> is
> >>      done on the basis of same fractions.
> >>
> >>   4. Let me explain this point
> >>
> >>      We pick up a real data event and calculate following
> >>      i)  Dbmax+- of real data event
> >>      ii) reshuffle charges in an event
> >>
> >>      iii) again calculate Dbmax+- and termed it Db+-max of charge
> >> reshuffle
> >>      iv)  calculate gamma of real data event
> >>      v)   calculate gamma of reshuffle event
> >>
> >>      Now for a given centrality
> >>      Steps i) to v) repeated for each event. Db+-max (data) and
> >> Db+-max(reshuffle)
> >>      sliced into ten percentile bins.
> >>      Now average gamma is found in every sliced Db+-max (data) and
> >> Db+-max(reshuffle)
> >>      from the respective event samples. It should be noted that
> >> events in the top
> >>      say 10% Db+-max(data) are not the same as in the top 10%
> >> Db+-max(reshuffle) i.e,
> >>      real events in the top 10% Db+-max(data) are different from
> >> those top 10%
> >>      Db+-max(reshuffle). Now the correlated background is caculated
> >> from the real events
> >>      corresponding to the top 10% Db+-max(reshuffle) events.
> >>
> >>       Please clarify the following
> >>
> >>       Of course you've also removed the large charge-shuffle
> >> background which is basically
> >>       an autocorrelation effect (sort to speak) due to the Dbmax (and
> >> Dbmax_shuffle)
> >>       selection bias.
> >>
> >>   5.  Db+-max distribution is sliced in to ten percentile bins which
> >> represent
> >>       different amount of charge separation in each sliced db+-max
> >> bin.
> >> Let us
> >>       say we have Db+-max = 2, in this case fractional dumbbell
> >> charge separation
> >>       f_DbCS = Db+-max-1=1 i.e., 100% back-to-back charge separation
> >> i.e.,
> >>       positive charged particles on one side of the dumbbell and
> >> negative charge
> >>       particles on other side of the dumbbell. So, computing gamma in
> >> different
> >>       Db+-max and calculating things is different from just making a
> >> single wide
> >>       bin as you mentioned. This method is designed to get  CME-like
> >> enriched sample
> >>       in given collision centrality as one divides all events into
> >> different collision
> >>       centralities depending on either the impact parameter or event
> >> multiplicity but
> >>       one does not study all events taken together without making
> >> different
> >>       collision centrality classes. However, for a single wide
> >> Db+-max bin as you
> >>       wrote we will get zero signal.
> >>
> >>       Please explain the following:
> >>
> >>       So is your finite signal really due to the difference between
> >> the average of ratios
> >>       and the ratio of averages (or perhaps also due to residual
> >> effect from shuffling)?
> >>
> >>
> >> Thank you,
> >>
> >> with regards,
> >> Jagbir Singh
> >>
> >>
> >>
> >> On 2020-11-18 23:18, Wang, Fuqiang wrote:
> >> > Hi Jagbir,
> >> >
> >> > Your results are quite interesting. I have a few further questions
> >> > about the details of your analysis:
> >> > 1. For each event you have Dbmax with the condition of |Dbasy|<0.25.
> >> > You bin events of each centrality in Dbmax. You use all events in
> >> > your analysis (i.e. you're not throwing away events based on Dbmax
> >> > or Dbasy), right?
> >> > 2. In your calculation of gamma=<...>/v2c for a particular Dbmax
> >> > bin of a given centrality, the v2c is calculated using those events
> >> > only, right?
> >> > 3. For the charge reshuffle, you reshuffle the charges of all
> >> > events, and repeat your analysis from step 1 (i.e. you treat this
> >> > as a completely separate "new" data sample), right? Did you
> >> > "randomize" the charges according to the positive/negative charge
> >> > ratio of the given event? On s11, the Dbmax_shuffle distribution is
> >> > a bit wider than the real distribution, do you understand why? How
> >> > do you bin the Dbmax and Dbmax_shuffle into 10 bins, respectively
> >> > (same bin edges or same fractions)?
> >> > 4. Your correlated background gamma is calculated for the Dbmax bin
> >> > where Dbmax is from the charge-shuffled events, but using restored
> >> > charges, right? If so, then you're effectively taking gamma
> >> > difference between Dbmax_i events and Dbmax_shuffle_i events (which
> >> > are different events), right? Of course you've also removed the
> >> > large charge-shuffle background which is basically an
> >> > autocorrelation effect (sort to
> >> > speak) due to the Dbmax (and Dbmax_shuffle) selection bias.
> >> > 5. You divide Dbmax (and Dbmax_shuffle) into 10 bins and do your
> >> > analysis in each bin separately, and then take the weighted average
> >> > for your f_cme result. You could just use a single wide Dbmax (and
> >> > Dbmax_shuffle) bin, then in principle you should get zero signal
> >> > because the correlated "background" is your real signal since they
> >> > are now identical event sample. So is your finite signal really due
> >> > to the difference between the average of ratios and the ratio of
> >> > averages (or perhaps also due to residual effect from shuffling)?
> >> >
> >> > This is a complicated analysis. It would be really good to have
> >> > more discussions so the details can flesh out better.
> >> >
> >> > Thanks,
> >> > Fuqiang
> >> >
> >> >
> >> >
> >> >> -----Original Message-----
> >> >> From: Star-fcv-l <star-fcv-l-bounces AT lists.bnl.gov> On Behalf Of
> >> >> jagbir via Star- fcv-l
> >> >> Sent: Tuesday, November 17, 2020 10:49 AM
> >> >> To: ShinIchi Esumi <esumi.shinichi.gn AT u.tsukuba.ac.jp>; STAR Flow,
> >> >> Chirality and Vorticity PWG <star-fcv-l AT lists.bnl.gov>
> >> >> Subject: Re: [Star-fcv-l] FCV PWG meeting, 18/Nov/2020 (Wed)
> >> >> 9:30am (New York time zone)
> >> >>
> >> >> Dear ShinIchi, Prithwish and Jiangyong,
> >> >>
> >> >> I would like to give "Update on event by event charge separation
> >> >> in
> >> >> Au+Au collisions at 200GeV with STAR detector"
> >> >>
> >> >> Please add me to agenda.
> >> >> I will post my slides later.
> >> >>
> >> >> Thankyou,
> >> >> Jagbir Singh
> >> >>
> >> >> On 2020-11-16 15:57, ShinIchi Esumi via Star-fcv-l wrote:
> >> >> > Dear FCV PWG colleagues
> >> >> > We will have our weekly FCV PWG meeting on coming Wednesday
> >> >> > 18/Nov/2020
> >> >> > 9:30AM (in BNL) at our usual time and place. So if you have
> >> >> > anything to present, please let us know and please post your
> >> >> > slide by
> >> Tuesday.
> >> >> > We'll talk about the "HLT express productions" in the beginning
> >> >> > of the meeting as you see in the agenda page. Jiangyong, please
> >> >> > send a link to your slide from last week.
> >> >> >
> >> >> > The zoom room link, ID and password are in our usual drupal
> >> >> > agenda page below.
> >> >> > Please also keep in mind that all the preliminary plots should
> >> >> > have already been there in the summary area below.
> >> >> > Best regards, Jiangyong, Prithwish and ShinIchi
> >> >> >
> >> >> > Meeting agenda page with zoom link :
> >> >> > https://drupal.star.bnl.gov/STAR/blog/jjiastar/bulkcorr
> >> >> >
> >> >> > Preliminary page :
> >> >> > https://drupal.star.bnl.gov/STAR/pwg/bulk-correlations/bulkcorr-
> >> >> > pre
> >> >> > lim inary-summary
> >> _______________________________________________
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