STAR Flow, Chirality and Vorticity PWG

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

A typo correction and clarification of my previous email.
Then we assume the non-biased value is in between -1 to 1 with a uniform 
distribution. So I present the result as 0 +- 1/sqrt(12), it means the 
non-biased value falls within +- 1/sqrt(12) with a probability of 
1/sqrt(12) which is exactly the probability of a standard deviation in 
uniform (-1, 1).

Best,
Diyu



On 2023-12-08 08:07, dshen via Star-fcv-l wrote:
> Hi Fuqiang,
>
> It seems we have an agreement on the first point, i.e. the result to
> lie between def - diff and def + diff. It doesn't say the diff should
> be the maximum, say, it has to be default to DCA<0.01 or <100.
>
> Regarding 1 sigma should be diff/sqrt(12) or 2*diff/sqrt(12), let me
> explain it in terms of probability.
> Let's take an example, say, the measured quantity is 0, and the
> variation is 1. Then we assume the non-biased value is in between -1
> to 1 with a uniform distribution. So I present the result as 0 +-
> 1/sqrt(12), it means the non-biased value falls within +- 1/sqrt(12)
> with a probability of 2*1/sqrt(12) which is exactly the standard
> deviation of 2*varition=2. If you define 1 sigma as
> 2*variation/sqrt(12), then we should present as +- half sigma to have
> the same probability as before.
>
> Thanks,
> Diyu
>
>
>
> On 2023-12-08 02:17, Wang, Fuqiang via Star-fcv-l wrote:
> > Hi Diyu,
> >
> > So the central issue is whether you get the maximum variation. If one
> > varies towards only one side, and quote +/- assuming the variation is
> > symmetric, then you’re really assuming the result to lie between min
> > def-diff and max diff+diff, so you should quote def +/- diff/sqrt(3).
> >
> > Best regards,
> > Fuqiang
> >
> > > On Dec 7, 2023, at 1:08 PM, Wang, Fuqiang <fqwang AT purdue.edu> wrote:
> > >
> > > ---- External Email: Use caution with attachments, links, or sharing 
> > > data ----
> > >
> > >
> > > Hi Diyu,
> > >
> > > I realize that there may be a misunderstanding on the term “max. 
> > > variation”. It means variations in cuts that result in maximum 
> > > variation in result.
> > >
> > > Regarding sqrt(12) vs sqrt(3):
> > > If one believes def. is min and sys. is max, then it’s probably 
> > > better to quote the average of def. and sys. as the central value and 
> > > +/- diff/sqrt(12) as the error.
> > > If there’s strong reason to quote the value to be the min. (or max. 
> > > for that matter) and the negative side error is really zero, then we 
> > > should quote the value as def.+diff/sqrt(3) not sqrt(12) because the 
> > > common understanding of error is that it covers 68% probability.
> > >
> > > Best regards,
> > > Fuqiang
> > >
> > > > On Dec 7, 2023, at 10:50 AM, dshen <dshen AT rcf.rhic.bnl.gov> wrote:
> > > >
> > > > [You don't often get email from dshen AT rcf.rhic.bnl.gov. Learn why 
> > > > this is important at 
> > > > https://urldefense.com/v3/__https://aka.ms/LearnAboutSenderIdentification__;!!P4SdNyxKAPE!HrVa2wHd3fzH5a6Dr0kh6WgIrrU2y5XXz4t2XzuC3J9-Pwp1Dh9szY1HZyJ18mNbUqk5PWsV8mJ1HGVk7kTAs3ZK0w$ 
> > > >  ]
> > > >
> > > > ---- External Email: Use caution with attachments, links, or sharing 
> > > > data ----
> > > >
> > > >
> > > > Hi Fuqiang,
> > > >
> > > > One sigma is |def.-sys.|/sqrt(12), and it shows as +- 1 sigma for 
> > > > the
> > > > case of (def. - |def.-sys.|,  def. + |def.-sys.|).
> > > > The critical point is that it doesn't require a maximum variation, 
> > > > it
> > > > just requires that the variation could cover the true value. The
> > > > confidence level is based on experience and common sense, there is 
> > > > no
> > > > mathematical way to quantify it - it is not statistics.
> > > >
> > > > Best,
> > > > Diyu
> > > >
> > > >
> > > > > > On 2023-12-07 23:28, Wang, Fuqiang wrote:
> > > > > Hi Diyu,
> > > > >
> > > > > What you wrote is just another way to say that the physics quantity 
> > > > > in
> > > > > question is within the min and max of (def. - |def.-sys.|,  def. +
> > > > > |def.-sys.|), respectively. In such a case, one would quote a sigma 
> > > > > of
> > > > > 2*|def.-sys.|/sqrt(12) = |def.-sys.|/sqrt(3). The essential point 
> > > > > is
> > > > > to demonstrate to reasonable confidence that this is indeed the
> > > > > maximum syst. variation in the result.
> > > > >
> > > > > Best regards,
> > > > > Fuqiang
> > > > >
> > > > > > On Dec 7, 2023, at 6:32 AM, dshen via Star-fcv-l
> > > > > > <star-fcv-l AT lists.bnl.gov> wrote:
> > > > > >
> > > > > > ---- External Email: Use caution with attachments, links, or 
> > > > > > sharing
> > > > > > data ----
> > > > > >
> > > > > >
> > > > > > Hi Fuqiang, Zhiwan and all,
> > > > > >
> > > > > > It was a inspiring discussion on the systematic uncertainty
> > > > > > calculations
> > > > > > yesterday, it pushes me to think.
> > > > > > I tend to agree with Zhiwan and what the blind-analysis did, i.e. 
> > > > > > use
> > > > > > denominator of 1/sqrt(12).
> > > > > > The argument was that one shouldn't divide the variation by 
> > > > > > 1/sqrt(12)
> > > > > > because the variation isn't proved to be the maximum - minimum, I
> > > > > > think
> > > > > > there is a misunderstanding of the reason behind it.
> > > > > > It isn't based on the assumption that the variation is maximum -
> > > > > > minimum, the underlying assumption is that the true value falls 
> > > > > > within
> > > > > > "default cut" +- "variation".
> > > > > > Let's take an example, say, the default cut is DCA<2, and the
> > > > > > systematic
> > > > > > cut is DCA<1.
> > > > > > The assumption is that the non-biased value is in the interval of
> > > > > > (def.
> > > > > > - |def.-sys.|,  def. + |def.-sys.|), and it can be any value in 
> > > > > > that
> > > > > > interval with equal probability (uniform distribution) assuming we
> > > > > > don't
> > > > > > have any pre-knowledge to the best position. That's the reason of 
> > > > > > why
> > > > > > people assign |def.-sys.|/sqrt(12) as 1 sigma and use two-side 
> > > > > > band.
> > > > > > It hasn't to be the maximum - minimum, although it isn't incorrect
> > > > > > technically to use larger uncertainty, say, use Dca<0.1 to 
> > > > > > Dca<100.
> > > > > > But
> > > > > > I think the principal is to provide the best estimate instead of 
> > > > > > the
> > > > > > most conservative value.
> > > > > > What variation can be considered as reasonable? I think it is 
> > > > > > based on
> > > > > > experience and common sense to a specific physics topic. For CME
> > > > > > study,
> > > > > > like what Zhiwan did, it is reasonable to assume the non-biased 
> > > > > > value
> > > > > > falls with in DCA<2 +- |DCA<2 - DCA<1|, for example.
> > > > > >
> > > > > > That's my two cents.
> > > > > >
> > > > > > Best,
> > > > > > Diyu
> > > > > >
> > > > > >
> > > > > >
> > > > > > > On 2023-12-06 05:10, Zhiwan Xu via Star-fcv-l wrote:
> > > > > > > Dear Conveners,
> > > > > > > I would like to update the paper proposal on the CME search in 
> > > > > > > STAR
> > > > > > > BES-II.
> > > > > > > Please kindly add me to the schedule.
> > > > > > >
> > > > > > > The paper proposal webpage:
> > > > > > >
> > > > > > > https://drupal.star.bnl.gov/STAR/blog/zhiwanxu/Paper-Proposal-Search-Chiral-Magnetic-Effect-RHIC-Beam-Energy-Scan-II
> > > > > > > The slides:
> > > > > > >
> > > > > > > https://drupal.star.bnl.gov/STAR/system/files/paper_proposal_CME_BESII_v2.pdf
> > > > > > >
> > > > > > > Best,
> > > > > > > Zhiwan
> > > > > > >
> > > > > > > ------------------------------------
> > > > > > > Zhiwan Xu,
> > > > > > > Department of Physics and Astronomy, UCLA
> > > > > > > zhiwanxu AT physics.ucla.edu
> > > > > > >
> > > > > > > ----- Original Message -----
> > > > > > > From: "subhash via Star-fcv-l" <star-fcv-l AT lists.bnl.gov>
> > > > > > > To: "STAR Flow, Chirality and Vorticity PWG"
> > > > > > > <star-fcv-l AT lists.bnl.gov>
> > > > > > > Cc: "subhash" <subhash AT rcf.rhic.bnl.gov>
> > > > > > > Sent: Sunday, December 3, 2023 11:21:34 PM
> > > > > > > Subject: [Star-fcv-l] FCV PWG meeting on 06/December/2023 Wed. 
> > > > > > > 9:30
> > > > > > > AM
> > > > > > > EDT
> > > > > > >
> > > > > > > Dear All,
> > > > > > >
> > > > > > > We shall have our weekly FCV PWG meeting this Wednesday 
> > > > > > > (06/Dec/2023)
> > > > > > > at
> > > > > > > 9:30 AM EDT. If you would like to present please let us know. 
> > > > > > > Please
> > > > > > > try
> > > > > > > posting your slides by Tuesday. The agenda will be collected at:
> > > > > > > https://drupal.star.bnl.gov/STAR/blog/jjiastar/bulkcorr
> > > > > > >
> > > > > > > Zoom details are copied below.
> > > > > > >
> > > > > > > Thanks and regards,
> > > > > > > Prithwish, Zhenyu and Subhash
> > > > > > >
> > > > > > >
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