STAR Correlations and Fluctuations PWG

[Nu Xu <nxu AT lbl.gov>]

Hi Mate and All,

Thank you for these explanation's.
All you have said is possible, but we should conclude with results, not 
speculations. The result should be presented in the talk.

Regards,
Nu

> On May 11, 2024, at 1:22 PM, Mate Csanad <csanad AT bnl.gov> wrote:
> 
> Hi Nu,
> 
> Sorry to amend myself, but there is an additonal point: if densities are 
> larger, freeze-out may happen later, and hence larger tails appear in the 
> freeze-out distribution. This may be the effect in the end that causes 
> alpha to decrease with increasing energy.
> 
> Best regards,
> Mate
> 
> 2024. 05. 11. 22:04 keltezéssel, Mate Csanad írta:
>> Hi Nu,
>> I am sorry if I misunderstand the point you raise, but maybe it helps 
>> clarifying things if I try to elaborate what Daniel is trying to say in 
>> the discussed slide.
>> The idea (speculation) is that the total hadron multiplicity is increasing 
>> with collision energy, and if this increase is faster than the 
>> quark-hadron (or chemical) freeze-out volume, then also hadron number 
>> density also increases with collision energy. In turn, this increase in 
>> density (and a possible increase in temperature) decreases the mean free 
>> path in the hadron gas phase. This is directly connected to the nature of 
>> diffusion, how anomalous it is, to what extent it differs from normal 
>> diffusion. The larger the difference, the more anomalous the diffusion is, 
>> the smaller alpha may become.
>> In other words, the following things happen with increasing collision 
>> energy:
>> 1) Increase in the number density of the hadron gas
>> 2) Decrease in the mean free path in the hadron gas
>> 3) More frequent hadron collisions, and more of them in total
>> 4) More anomalous nature of hadron diffusion (in the hadron gas)
>> 5) Smaller alpha values, i.e., larger tails of the spatial distribution of 
>> the last points of scattering (hadron kinetic freeze-out distribution)
>> This line of argumentation in fact can be checked in UrQMD, or any simle 
>> hadron gas model, how the spatial freeze-out distributions change with 
>> collision energy - was however not yet done. What is known (published) is 
>> that in EPOS (including UrQMD), alpha is a bit smaller at LHC than at top 
>> RHIC energy. Furthermore, Daniel's recent UrQMD results indicate that 
>> alpha is even larger in pure UrQMD at 3.2 or 3.9 GeV (and there is also a 
>> small increase from 3.9 to 3.2 GeV ).
>> I'm not sure if this clears the point to be conveyed, but Nu, please let 
>> Daniel and me know if we misunderstood what you wrote.
>> Thanks, best regards,
>> Mate
>> 2024. 05. 11. 16:56 keltezéssel, Nu Xu via Star-cf-l írta:
>>> Dear Daniel and All,
>>> 
>>> Thank you for the quick responses.
>>> Regarding to the first reply to my first point, I am still not convinced.
>>> Two particle correlations do not ‘see' the density because it only be 
>>> effective when the strong interactions are ceased. Source size parameters 
>>> do not reflected direct the size ( -> density) due to other effects such 
>>> as collective flow.
>>> 
>>> The claim of density effect could be misleading.
>>> 
>>> Regards,
>>> Nu
>>> 
>>>> On May 11, 2024, at 5:18 AM, Kincses Dániel <kincses AT ttk.elte.hu> wrote:
>>>> 
>>>> Dear Hanna, Nu,
>>>> Thank you for the comments and suggestions, I updated the slides 
>>>> accordingly.
>>>> I also compiled a list of answers here:
>>>> https://urldefense.com/v3/__https://docs.google.com/document/d/1ukHI7AjBrvGqx38Rw92UbKR8o-YjG7i_s6NkDqQ3Gsw/edit?usp=sharing__;!!P4SdNyxKAPE!CZR6W96_ct1ht2jBBbzhX_QQcYy3nG_lF2UMvvYdbS4Fd36N1EHQ3ub83NIVl_9Nd9POaT-FWItK2Sw1Pso$
>>>> 
>>>> Thanks,
>>>> Daniel
>>>> 
>>>> Feladó: Star-cf-l <star-cf-l-bounces AT lists.bnl.gov>, meghatalmazó: Nu Xu 
>>>> via Star-cf-l <star-cf-l AT lists.bnl.gov>
>>>> Elküldve: 2024. május 11., szombat 4:01
>>>> Címzett: STAR Correlations and Fluctuations PWG <star-cf-l AT lists.bnl.gov>
>>>> Másolatot kap: Nu Xu <nxu AT lbl.gov>
>>>> Tárgy: Re: [Star-cf-l] STAR presentation by Daniel Kincses for CPOD 2024 
>>>> submitted for review
>>>>   Dear Daniel and All,
>>>> 
>>>> I agree with all comments/suggestions offered by Hanna.
>>>> In addition, I have the following two suggestions:
>>>> 
>>>> 1) slide 19 - Summary: (i) “Increasing particle density → rescattering 
>>>> decreases 𝜶?”  the HBT refers to the freeze-out particle correlation. 
>>>> Why does it sensitive to density before freeze-out? It appears that at 
>>>> higher collision energy or more central collisions, the source is 
>>>> further away from Gaussian. I suggest remove the speculation. (ii) Lower 
>>>> - right figure: remake the plot till x-axis to 300 GeV;
>>>> 
>>>> 2) slide 18 - last bullet: replace "No non-monotonic trend observed yet” 
>>>> by “No non-monotonic trend in alpha observed yet”;
>>>> 
>>>> Hope this is helpful.
>>>> 
>>>> Nu
>>>> 
>>>> On May 10, 2024, at 3:34 PM, Hanna Paulina Zbroszczyk via Star-cf-l 
>>>> <star-cf-l AT lists.bnl.gov> wrote:
>>>> 
>>>> Dear Daniel,
>>>> 
>>>> Thanks for your update, I have a few more remaining comments:
>>>> 
>>>> Slide 3:
>>>> I still don’t understand why S function depends on spatial and momentum 
>>>> coordinates.
>>>> Provide a reference here. Why do you use different to Koonin-Pratt 
>>>> equation?
>>>> 
>>>> Slide 4:
>>>> Once more about the statement dla Levy shape of the correlation function 
>>>> is not a consequence of conversion from 3D to 1D case. Can you prove 
>>>> this? Do you have any example that if your source can be described by 
>>>> Gaussian distributions in 3D, you will end up with Gaussian in 1D as 
>>>> well?
>>>> 
>>>> Slide 6:
>>>> Again: speaking about critical behavior, do you have prediction of D(r) 
>>>> when \alpha is 0.5?
>>>> Do you have an example of the correlation function for such a case?
>>>> 
>>>> Slide 15:
>>>> Can you discuss here how S_{core} and S_{halo} look like?
>>>> 
>>>> Slide 18:
>>>> I suggest not to discuss CMS results, especially when you don’t show 
>>>> them (which is ok).
>>>> 
>>>> Kind regards,
>>>> Hanna
>>>> 
>>>> Prof. Hanna Zbroszczyk, PhD, DSc, Eng.
>>>> E-mail: hanna.zbroszczyk AT pw.edu.pl
>>>> Tel: +48 22 234 5851 (office)
>>>> 
>>>> Address:
>>>> Warsaw University of Technology
>>>> Faculty of Physics
>>>> Nuclear Physics Division
>>>> Koszykowa 75
>>>> Office: 117b (via 115)
>>>> 00-662 Warsaw, Poland
>>>> 
>>>> 
>>>> 
>>>> Wiadomość napisana przez webmaster--- via Star-cf-l 
>>>> <star-cf-l AT lists.bnl.gov> w dniu 06.05.2024, o godz. 17:12:
>>>> 
>>>> Dear star-cf-l AT lists.bnl.gov members,
>>>> 
>>>> Daniel Kincses (kincses AT ttk.elte.hu) has submitted a material for a 
>>>> review,
>>>> please have a look:
>>>> https://drupal.star.bnl.gov/STAR/node/67691
>>>> 
>>>> Deadline: 2024-05-20
>>>> ---
>>>> If you have any problems with the review process, please contact
>>>> webmaster AT www.star.bnl.gov
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