STAR Flow, Chirality and Vorticity PWG

[jagbir <jagbir AT rcf.rhic.bnl.gov>]

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-prelim
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