STAR Correlations and Fluctuations PWG

[Sooraj Radhakrishnan <skradhakrishnan AT lbl.gov>]

Date: 08/23/2024

Participants: Bijun Fan, Li'Ang Zhang, Yaping Wang, Yingjie Zhou, Youquan Qi, Jae Nam, Ting Ling, Xiaoxuan Chu, Hanna Zbroszczyk, Nu Xu, Richard Seto, Subhash Singha, Isaac Mooney, Nihar Sahoo, Yi Yang, Guannan Xie, Shuai Yang, Yue Hang Leung, ShinIchi Esumi, Sooraj Radhakrishnan

Title: Collision Energy Dependence of Kaon Femtoscopy in High Baryon Density Region

PAs: Wensong Cao, Bijun Fan, Youquan Qi, Li’Ang Zhang, Xin Dong, Chuan Fu, Xiaofeng Luo, Shusu Shi, Yaping Wang, Nu Xu, Yingjie Zhou

Target journal: PRL/PLB

Proposal page: https://drupal.star.bnl.gov/STAR/blog/lazhang/WebPage-Energy-dependence-Kaon-correlation-function-high-baryon-density-region

Presentation:https://drupal.star.bnl.gov/STAR/system/files/KKCF20240823PWGC_0.pdf

The PWGC panel previewed a paper proposal from CF PWG. The panel found that the analysis is mature and results are important and interesting, and the paper should move forward. The journal choice was also found to be appropriate. The following points were discussed.

Q: On Fig.4. isn't 1/sqrt{mT} the expected mT scaling? So aren't kaons following mT scaling?

A: Yes, this is the expectation from a thermalized medium. Kaons follow the mT scaling. But the pions do not follow the scaling

Q: Are the pion results also part of this paper?

A: Yes. See Fig.3, 4

Q: Can you quantify how much pions deviate from mT scaling?

A: The deviation is very strong. We will add the table 

Q: S.12, Do you have a plot of the correction factor double ratio? This correction factor could depend on the radius. Or do you have the ideal and smear correlations from the embedding? Are these correlations similar to that in the data?

A: Don't have in this presentation, but will add

Q: On Fig.4, do you understand why 3.5 GeV both R_inv and lambda show deviation for charged kaons?

A: We did not find any reasons, we expect that this is from statistical fluctuations 

Q: Can you quantify the deviation at 3.5 GeV?

A: Yes, we will do

Q: On Fig.4, how is the asymmetry evaluated and how are the uncertainties calculated?

A: For charged kaons, this is from the difference in yields. For neutral kaons,  it is using equation shown in S.3. Particle - anti-particle will contribute to the final state strong interactions and particle - particle or anti-particle - ant-particle won't. When epsilon is 0, there is no asymmetry 

C: The error bars are large, have to careful how to word the decreasing trend of the asymmetry with energy

A: Yes, will do

Q: On Fig.3, For K0s at 3 GeV, the first point deviates from the fit. Does this impact the extracted values?

A: We include the variation of fitting range as a source of systematic uncertainty to take into account this

Q: On Fig.3, what is the difference between solid and open black circles?

A:  Black circles are the measured and the open circles are with only the quantum statistics, without final state interactions 

Q: Should the fit to the black data points be also shown? To show the quality?

A: This may make the plot very busy

Q: Do you plan to redo the analysis with the newer production, particularly with the updated alignment?

A: Yes, we plan to do that

Q: From Fig.4, the conclusion is drawn that pions and kaons are not in equilibrium. Given pions get other contributions, fo e.g from resonances are since kaons follow mT scaling, can we make this statement?

A: The mT dependence is less affected by these effects. Also at these low energies the resonance contribution to pions are small 

Q: What is the mT dependence at higher collision energies?

A: At higher collision energies they show 1/sqrt{mT} dependence. This is shown by the solid line 

C: Could consider changing marker symbols for different energies

Q: In the title, should the collision energies be specified instead of saying high baryon density?

A: There are no other measurements for kaons at high mu_B, we prefer to keep this

Q: Should pions also be indicated in the title?

A: We will discuss with PAs

--

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