STAR Flow, Chirality and Vorticity PWG

[Barbara Trzeciak <barbara.trzeciak AT gmail.com>]

Hi Qian,

we understand your concerns regarding the signal extraction. There are certainly a few things that are still due to be checked, we went with Diyu through his analysis procedure. However, overall the methods he's using are correct and he already takes into account many sources of the systematic uncertainties, and many variations are conservative.

One of the effects you're pointing out, which in case of your analysis is not small, in case of Diyu's measurement that has both sizable statistical and systematic uncertainties is well within these uncertainties. 

We therefore decided to release these preliminary results. And we can add a note on the slide that work on the systematic uncertainties is ongoing - or something similar. It's not a precision measurement that will provide drastically different physics message with a few percentage variation w.r.t. what we currently have.

This doesn't mean that your results cannot be approved later. You're using second order, and the two measurements don't even have to give exactly the same results. 

It also doesn't mean that after QM he won't follow up on all the checks and suggestion that you've provided.

Cheers,

Barbara 

On Sun, 3 Sept 2023, 07:37 tc88qy via Star-fcv-l, <star-fcv-l AT lists.bnl.gov> wrote:

Hi Diyu

    can you tell me how did you do the mix-event normalization range?
So, I can understand how did you do it.
If the correction is purely for acceptance according to your study,
then we can compare J/psi correction shape and raw data directly. Am I
understand correctly?

Qian Yang

On 2023-09-02 00:04, dshen wrote:
> Hi Qian,
>
> Sure, no problem, any specific and scientific comments/questions are
> always welcome.
> Regarding to the crystalball fitting, I firstly fit the costheta*
> integrated invariance mass distribution, in this fitting there are
> limitations for J/Psi shape, like the center mass range. Then I fixed
> the J/Psi shape in each costheta* bin to extract the yields and
> backgrounds.
> Regarding to the fitting range, I couldn't check it for now because I
> am on the way to QM with my old laptop. All the materials are on my
> working computer. Form you experience, can you estimate how large this
> effect will be? Will it lead to different conclusion if consider the
> current error bar?
>
> Best,
> Diyu
>
>
>
> On 2023-09-01 21:02, tc88qy wrote:
>> Hi Diyu and all
>>    First of all, I want to bring it up that every people at STAR have
>> the right to express his/her concern about any analysis.
>> I also working on the same data and the same topic. The student Dandan
>> and I also did the J/psi polarization measurement by using exact the
>> same data set. The only different between spin alignment and
>> polarization measurement is the different reference z-axis. Dandan's
>> results will be present at the coming quark matter conference and got
>> approved by HP pwg.
>>    This two analysis have very similar method.  The concern I bring it
>> up because we have encountered such problem in the J/psi polarization
>> measurement. And from you comparison between crystal-ball and guassian
>> function, it already prove that the yield extraction will affect the
>> final results. By just changing the signal function, the rho00 central
>> value changes are comparable with statistic uncertainty in Ru+Ru
>> 40-80%.
>>    I did not know how did you do the fitting. The experience we have
>> is that J/psi shape (crystal-ball function) can not take as a free
>> parameter in the fitting.
>>    The fitting range of 2.6-3.6 GeV/c is a litter big narrow. There is
>> about 20-30% of J/psi yields are below 3 GeV/c2. Like in the pp
>> system, J/psi bin counting range is 2.7-3.3 GeV/c2 at STAR. You should
>> extend your fitting range to lower mass range, so that it will have a
>> better control on residual background.
>>
>> Qian Yang
>>
>> On 2023-08-31 18:11, dshen via Star-fcv-l wrote:
>>> Regardless of wether we should show J/Psi at QM, as the author I feel
>>> my duty to defend the reliability of my plot.
>>> So I checked with crystalball function instead of a simple Gaussian
>>> function. The variation is small.
>>> I acknowledge this plot can be improved in the future, but I don't
>>> think the physics message could be wrong (no J/Psi spin alignment
>>> relative to ZDC plane is observed).
>>> I am a careful people, no more no less.
>>>
>>> Thanks,
>>> Diyu
>>>
>>>
>>> On 2023-08-28 23:41, dshen wrote:
>>>> Dear Conveners,
>>>>
>>>> Here are our preliminary request for J/Psi spin alignment
>>>> measurement
>>>> relative to 1st order ZDC event plane.
>>>> https://drupal.star.bnl.gov/STAR/system/files/JPsiPreliminaryRequest.pdf
>>>>
>>>> Thanks,
>>>> Diyu
>>>>
>>>> On 2023-08-23 14:24, Sooraj Radhakrishnan via Star-fcv-l wrote:
>>>>> Hi Gavin,
>>>>>    These are nice results and quite interesting. I have a question
>>>>> on
>>>>> the rapidity dependence. The observed rapidity dependence is quite
>>>>> strong, and also the value of rho_00 for y < 0.5 is quite close to
>>>>> 1/3. I see that for efficiency correction you use a flat
>>>>> distribution
>>>>> in rapidity. At these energies is this a reasonable distribution to
>>>>> use? Do you have any systematics on the impact of the rapidity
>>>>> distribution used on efficiency evaluation?
>>>>>
>>>>> For the theory calculation, is this the same model as in the nature
>>>>> paper? Could you add the reference? Are there any assumptions in
>>>>> getting the rapidity dependence? Why wouldnt we see the
>>>>> spin-alignment
>>>>> at mid-rapidity, and see large values at forward rapidity?
>>>>> Shouldn't
>>>>> the physics causing spin alignment be present at mid-rapidity too?
>>>>> I
>>>>> see on your S33 the explanation that the values are linked to
>>>>> motion
>>>>> of the particle. Is this a trivial kinematic effect? The px, py, pz
>>>>> here are in lab frame?
>>>>>
>>>>> thanks
>>>>> Sooraj
>>>>>
>>>>> On Thu, Aug 17, 2023 at 9:06 PM Gavin Wilks via Star-fcv-l
>>>>> <star-fcv-l AT lists.bnl.gov> wrote:
>>>>>
>>>>>> Dear FCV Convenors,
>>>>>>
>>>>>> My preliminary request for QM2023 φ-meson global spin alignment
>>>>>> analysis can be found here:
>>>>>>
>>>>> https://drupal.star.bnl.gov/STAR/system/files/userfiles/6551/PreliminaryRequest_QM2023_FoldedRapidity.pdf
>>>>>>
>>>>>> Best,
>>>>>> Gavin_______________________________________________
>>>>>> Star-fcv-l mailing list
>>>>>> Star-fcv-l AT lists.bnl.gov
>>>>>> https://lists.bnl.gov/mailman/listinfo/star-fcv-l
>>>>>
>>>>> --
>>>>>
>>>>> Sooraj Radhakrishnan
>>>>>
>>>>> Research Scientist,
>>>>> Department of Physics
>>>>>
>>>>> Kent State University
>>>>>  Kent, OH 44243
>>>>>
>>>>> Physicist Postdoctoral AffiliateNuclear Science Division
>>>>> Lawrence Berkeley National Lab
>>>>> MS70R0319, One Cyclotron Road
>>>>> Berkeley, CA 94720
>>>>> Ph: 510-495-2473 [1]
>>>>>
>>>>> Email: skradhakrishnan AT lbl.gov
>>>>>
>>>>>
>>>>> Links:
>>>>> ------
>>>>> [1] tel:%28510%29%20495-2473
>>>>> _______________________________________________
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>>>
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