STAR Flow, Chirality and Vorticity PWG

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

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:
>
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> 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.
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>>>> Thanks and regards,
>>>> Prithwish, Zhenyu and Subhash
>>>>
>>>>
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