STAR Flow, Chirality and Vorticity PWG

[Sooraj Radhakrishnan <skradhakrishnan AT lbl.gov>]

Hi Shinichi, Prithwish,
   Thanks for the slides and comments

Regarding the v1 difference and hadro comparisons, there are a couple of points to note 

1) The difference in v1 between protons and anti-protons is explained using different initial tilted distributions for the bulk and for transported protons. There is no independent constraint on this and the tilts are tuned to data. In other words, the difference in the final state v1 is carried over to the difference in initial distributions - but without an independent constraint. So doesnt have much predictive power or helps explaining the v1 difference we see. Please find some more details here https://arxiv.org/pdf/2211.15659

2) What is interesting though is that the centrality dependence is explained through baryon diffusion. As you can see on S.37 here https://drupal.star.bnl.gov/STAR/system/files/FCV_Comments_Measurement%20of%20system%20size%20dependence%20of%20directed%20flow%20of%20protons%20%28anti-protons%29%20at%20RHIC_2.pdf, its the baryon diffusion that makes the difference go negative in peripheral collisions. The initial tilt difference is such that the proton v1 gets a positive contribution compared to anti-proton v1. Without the diffusion the difference doesnt go negative. Not sure, but I think its possible, constraints on the baryon diffusion can be checked with other measurements, for example on spectra or v2 

In short its the baryon inhomogeneity coupled with baryon diffusion that produced negative delta v1 in hydro calculations. Thought that is useful to point out

Best,
Sooraj

On Sun, Dec 1, 2024 at 6:41 PM EsumiShinIchi <esumi.shinichi.gn AT u.tsukuba.ac.jp> wrote:

Dear Prithwish and Diyu
Thank you very much for the suggestions, ALICE D0-D0bar are already included.
Let’s discuss whether we want to move this to Friday or not. I’ll try to include
the Lambda results.
Best regards, ShinIchi

> 2024/12/02 10:48、Diyu Shen <dyshen AT fudan.edu.cn>のメール:
>
> Hi Prithwish and ShinIchi,
>
> I think for this topic it is necessary to include all the results in heavy-ion experiment, not only from STAR but also from ALICE.
> So I would suggest to discuss D meson splitting observed by ALICE after point 5.
>
> Say D-Dbar results show 2.8 sigma splitting, despite D’s have no electrical charge — challenges naive EM-field explanation.
>
> Best,
> Diyu
>
>
>> On Dec 2, 2024, at 05:05, Prithwish Tribedy <ptribedy AT rcf.rhic.bnl.gov> wrote:
>>
>> Hi ShinIchi and all,
>> Thank you for the excellent compilation! Should we consider moving your v1​ talk to Friday? This would allow you to include both public and STAR internal results, providing more flexibility to address key issues that support or challenge EM-field explanations. I list a few points for you to consider on both support and apparent challenge to EM-field explanations:
>>
>>   1. Proton results change sign with centrality across all energies -- supports naive EM-field expectations
>>   2. Kaon results follow proton trends but are weaker -- supports EM-field if we assume strange quark behave differently
>>   3. Pion results align with protons/kaons at low energies, pion-proton-kaon all showing same trend -- challenging transport-only explanations.
>>   4. Above (#3) may not be the case for 200 GeV, it's unclear if pion results change sign like protons at 200 GeV -- points to something is missing in our understanding
>>   5. Net-ΛΛ results are almost on top of protons, despite Λ's have no electric charge -- challenges naive EM-field explanation
>>   6. Splitting increases with ΔqΔq, ΔBΔB, and ΔSΔS, if you assume NCQ scaling holds for produced particles -- supports both EM-field & has been explained by hydro models with baryon inhomogeneity
>>   8. NCQ scaling -- crucial but is hard to verify, attempt made for produced quarks only with limited significance, but there are proof that it does not hold for mixture of produced & transported quarks
>>   7. Hydro models explain proton data without EM fields -- challenging EM explanations
>>   8. Hydro models has not demonstrated that they can explain all PID data -- incompleteness to hydro models that challenge EM-field explanations
>>   9. Other models such as mean field -- I am not an expert but it's worth touching.
>>
>> Overall, this is a fascinating topic that deserves lengthy discussion, so having it as the last talk of the day may not be ideal.
>>
>> Let me know your thoughts!
>>
>> Best,
>> Prithwish
>>
>>
>> On 2024-12-01 12:40, EsumiShinIchi wrote:
>>> Dear Rich, Subhash, Prithwish and all
>>> I send you the draft of my talk on v1 splitting with materials that
>>> are already in public,
>>> if you have any suggestions, please let me know. Thank you very much
>>> in advance.
>>> Best regards, ShinIchi
>>> https://drupal.star.bnl.gov/STAR/system/files/v1split_bes2star_Esumi_2024Dec04.pdf
>>>> Hi Everyone
>>>> I like Subash’s suggestion
>>>> To be clear it is now
>>>> Sooraj - v1, v2 (and v3?) of light and strange hadrons and
>>>> implications
>>>> Chengdong Han - light and hyper nuclei flow
>>>> Xingrui Gou - Global and local polarization in BES-II COL (note that
>>>> we intend to make FXT-polarization a separate talk)
>>>> Zhiwan Xu - Chiral effects (CME related) in BES-II and 200GeV
>>>> Shinichi - v1 splitting and possible interpretations
>>>> Pretty good. Hope we can fit it all in. I think at least Sooraj and
>>>> Shinichi’s talks should be in the open session with the theorists
>>>> -Rich
>>>>> Dear Sooraj, ShinIchi, Richard and Prithwish,
>>>>> My understanding is that we were looking for candidates whose
>>>>> talks could present an unbiased perspective on topics such as the
>>>>> onset of partonic collectivity (bringing together all viewpoints)
>>>>> and the electromagnetic field (covering both electromagnetic and
>>>>> non-electromagnetic scenarios). However, we did not reach a
>>>>> consensus on the EM-talk.
>>>>> Therefore, may I suggest having ShinIchi give a summary talk on
>>>>> the experimental results of v1-splitting from STAR (if possible
>>>>> and if you agree), followed by a theorist? I would recommend
>>>>> Sandeep Chatterjee to discuss v1 with hydrodynamics. He is an
>>>>> expert on v1 splitting due to EM (predicted D-meson v1 splitting)
>>>>> and non-electromagnetic scenario with baryon. This talk could be
>>>>> part of an open session, as most of our v1 results are public.
>>>>> Although I don't see much space in agenda to accommodate
>>>>> v1-splitting theory speaker,  I’m cc’ing ShinIchi here to get
>>>>> his opinion on this.
>>>>> The followings are rest of the talks from FCV:
>>>>> Sooraj - Summarizing v1, v2 of light and strange hadrons
>>>>> Chengdong Han - light and hyper nuclei flow
>>>>> Xingrui Gou - Global and local polarization in BES-II COL (note
>>>>> that we intend to make FXT-polarization a separate talk)
>>>>> Zhiwan Xu - Chiral effects (CME related) in BES-II and 200GeV
>>>>> Thanks and regards,
>>>>> Subhash
>

--

Sooraj Radhakrishnan

Research Scientist,

Department of Physics

Kent State University

Kent, OH 44242

Physicist Postdoctoral Affiliate

Nuclear Science Division
Lawrence Berkeley National Lab
MS70R0319, One Cyclotron Road

Berkeley, CA 94720

Ph: 510-495-2473

Email: skradhakrishnan AT lbl.gov