STAR Flow, Chirality and Vorticity PWG

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

Hi Diyu,

You say
“We don't have to scan the DCA to find the min and mix number, we just
need to find a reasonable range that we are confident to cover the
non-biased value.”

But how?

Best regards,
Fuqiang

> On Dec 7, 2023, at 9:51 PM, dshen <dshen AT rcf.rhic.bnl.gov> wrote:
>
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>
> Hi Fuqiang,
>
> I disagree with this statement:
> "For example, just for the sake of illustration, it is possible that
> DCA<1.5 cm gives the min. result and DCA<0.8 cm gives the max result,
> however, one would have to scan the DCA space to know this."
> We don't have to scan the DCA to find the min and mix number, we just
> need to find a reasonable range that we are confident to cover the
> non-biased value. Certainly you will have a large variation if you use
> DCA<0.01 - there are only few tracks, but we don't use it based on
> common sense.
>
> Best,
> Diyu
>
>
>> On 2023-12-08 10:30, Wang, Fuqiang wrote:
>> Hi Diyu,
>>
>> Please see comments in color below.
>>
>> Best regards,
>> Fuqiang
>>
>> -------------------------
>>
>> From: dshen <dshen AT rcf.rhic.bnl.gov>
>> Sent: Thursday, December 7, 2023 7:07 PM
>> To: STAR Flow, Chirality and Vorticity PWG <star-fcv-l AT lists.bnl.gov>
>> Cc: Wang, Fuqiang <fqwang AT purdue.edu>
>> Subject: Re: [Star-fcv-l] Discussion of systematic uncertainty
>> calculation - FCV PWG meeting on 06/December/2023 Wed. 9:30 AM EDT
>>
>> [You don't often get email from dshen AT rcf.rhic.bnl.gov. Learn why this
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>>   [1] ]
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>>
>> 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.
>>
>> Just to make sure we're on the same page: If we say the results lie
>> between def - diff and def + diff, we mean these are min and max. We
>> do have to make reasonably sure these are the min-max range. They of
>> course do not have to come from the min-max range of the cut, as the
>> result may not linearly depend on the cut. For example, just for the
>> sake of illustration, it is possible that DCA<1.5 cm gives the min.
>> result and DCA<0.8 cm gives the max result, however, one would have to
>> scan the DCA space to know this.
>>
>> 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.
>>
>> For a flat distribution of width 2, the equivalent Gaussian sigma is
>> 2/sqrt(12). So the error is +/- 2/sqrt(12). It is +/- 1/sqrt(3) or
>> approximately +/- 0.6, or 1.2 out of 2, i.e. 60%.
>>
>> 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:
>>>>
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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:
>>>>>
>>>>> [You don't often get email from dshen AT rcf.rhic.bnl.gov. Learn
>> why
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>> [2]
>>>>> ]
>>>>>
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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
>> [3]
>>>>>>>> The slides:
>>>>>>>>
>>>>>>>>
>> https://drupal.star.bnl.gov/STAR/system/files/paper_proposal_CME_BESII_v2.pdf
>> [4]
>>>>>>>>
>>>>>>>> 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
>> [5]
>>>>>>>>
>>>>>>>> Zoom details are copied below.
>>>>>>>>
>>>>>>>> Thanks and regards,
>>>>>>>> Prithwish, Zhenyu and Subhash
>>>>>>>>
>>>>>>>>
>>>>>>>> ZOOM LINK FOR FCV MEETING:
>>>>>>>> Join ZoomGov Meeting
>>>>>>>>
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