STAR Flow, Chirality and Vorticity PWG

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

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:
>
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>
> 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:
>>>>
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>>>> 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
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>>>>> Prithwish, Zhenyu and Subhash
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