STAR Flow, Chirality and Vorticity PWG

[Prithwish Tribedy <ptribedy AT rcf.rhic.bnl.gov>]

Dear Qiang,

Nice abstract! Please consider the following comments on version 2.

General comments: Your original abstract is a bit longer. I have 
proposed to shorten it a bit by like 20 words. The reference you have 
added are ok but not the best suited for the context. The 
McLerran-Skokov paper is about B-field with conductivity, but I am not 
sure it talks about Lambda polarization, you can keep it and I don't 
have a more appropriate suggestion at this moment. The PRL paper by Fu 
et al talks about shear-induced vorticity, again the context is not 
clear.

Here are my text suggestion:

"A significant non-zero global spin polarization of $\Lambda$ hyperons 
by STAR collaboration in the 1st phase of RHIC Beam Energy Scan (BES) 
provided the evidence of enormous vorticity in Quark Gluon Plasma (QGP) 
medium induced by the large angular momentum interactions. In these 
studies, there is a hint of larger $\bar{\Lambda}$ global polarization 
relative to $\Lambda$, consistent with expectation from a strong 
late-stage magnetic field sustained by the QGP. Such a splitting could 
reveal information about the electric conductivity of the QGP, and is 
therefore of great interest [1]."

-->

"STAR's measurement of a significant global spin polarization of 
$\Lambda$ hyperons in the first phase of RHIC BES provides evidence of 
vorticity in the QGP. The data also hinted at a larger polarization of 
$\bar{\Lambda}$, which is expected from a strong late-stage magnetic 
field sustained by the medium. A decisive experimental test of this 
splitting would be highly significant, as it could reveal valuable 
information about the electric conductivity of the QGP [1]."


"Recent theoretical calculations also indicate that the gradient of 
baryonic chemical potential (analogous to the electric field) can induce 
a sizable spin Hall current in Au+Au collisions at 
$\sqrt{s_{\mathrm{NN}}}$ $\sim$ 10 GeV. The predicted pattern and energy 
dependence of the difference between local polarization of $\Lambda$ and 
$\bar{\Lambda}$ hyperons ($P_x^\mathrm{net} \sin(2\Psi_2 - \phi_p^\ast), 
P_y^\mathrm{net} \cos(2\Psi_2 - \phi_p^\ast), P_z^\mathrm{net} 
\sin(2\Psi_2 - \phi_p^\ast)$, $P_{x,y,z}^\mathrm{net} = 
P_{x,y,z}^{\Lambda} - P_{x,y,z}^{\bar{\Lambda}}$, where $\Psi_2$ is the 
second-order event-plane angle and $\phi_p^\ast$ is the azimuthal angle 
of the proton in $\Lambda$'s rest frame) at RHIC BES energies are 
significantly different with and without the presence of baryonic spin 
Hall current [2,3]."

-->

"Similarly, the local polarization of $\Lambda$ and $\bar{\Lambda}$ 
hyperons are predicted to be different due to the gradient of baryonic 
chemical potential (analogous to the electric field) induced by the spin 
Hall effect. This effect is expected to be observable through the energy 
dependence of the angular modulation of the net polarization, 
$P^\mathrm{net}_{x,y,z} = P^\Lambda_{x,y,z} - 
P^{\bar{\Lambda}}_{x,y,z}$, as measured by 
$P^\mathrm{net}_{x,z}\sin(2\Psi_2-\phi_p^*)$ and 
$P^\mathrm{net}_{y}\cos(2\Psi_2-\phi_p^*)$, where $\Psi_2$ is the 
second-order event-plane angle and $\phi_p^*$ is the azimuthal angle of 
the proton in $\Lambda$'s rest frame [2,3]."



"During the 2nd phase of BES, STAR has collected high-statistics data 
sets with upgraded detectors, allowing precision measurements of 
polarization difference. In this talk, we will present the splitting in 
global and local spin polarization of Λ hyperons in RHIC BES-II Au+Au 
collisions at √sNN =7.7, 11.5, 14.6, 19.6, and 27 GeV."

-->

We report the first measurement of splitting in global and local spin 
polarization of $\Lambda$ hyperons in heavy ion collisions using data 
collected by the STAR experiment during the second phase of the RHIC 
Beam Energy Scan (BES II) with the upgraded STAR detector. We used Au+Au 
collisions at $\sqrt{s_{\mathrm{NN}}} = 19.6$ and 27 GeV for the former, 
and the same collision system at $\sqrt{s_{\mathrm{NN}}} = 7.7--27$ GeV 
for the latter, covering a wide range of energies.

"The polarization measurements will also be presented differentially as 
a function of centrality, transverse momentum, and rapidity."

-->

"We will also present the polarization measurements as a function of 
centrality, transverse momentum, and rapidity."

"These global and local polarization measurements will help reveal 
information about the late-stage magnetic field sustained by the QGP, as 
well as probe predicted Spin Hall currents in a highly dense baryonic 
environment."

-->

"Our measurements provide important insights on the late-stage magnetic 
field sustained by the QGP, as well as probe predicted spin Hall 
currents in a highly dense baryonic environment."


Best,
Prithwish



On 2023-04-18 23:20, webmaster--- via Star-fcv-l wrote:
> Dear star-fcv-l AT lists.bnl.gov members,
>
> Qiang Hu (qianghu AT impcas.ac.cn) has submitted a material for a review, 
> please
> have a look:
> https://drupal.star.bnl.gov/STAR/node/63469
>
> Deadline: 2023-05-01
> ---
> If you have any problems with the review process, please contact
> webmaster AT www.star.bnl.gov
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