STAR Correlations and Fluctuations PWG

[Takafumi Niida <niida AT bnl.gov>]

Date: Dec/16/2022

Participants: Sebastian Siejka, Hanna Zbroszczyk, Pawel Szymanski, Diana Pawlowska, Daniel Wielanek, Barbara Trzeciak, Maria Zurek, Nihar Sahoo, Prithwish Tribedy, Subhash Singha, Xiaoxuan Chu, Yi Yang, Yue-Hang Leung, Rongrong Ma, Takafumi Niida

Title: Proton femtoscopy in Au+Au collisions at BES energies in RHIC

PAs: Sebastian Siejka, Hanna Zbroszczyk, Pawel Szymanski, Diana Pawlowska, Daniel Wielanek

Target journal: PRC

Proposal page: https://drupal.star.bnl.gov/STAR/blog/siejka/Paper-proposal-Proton-femtoscopy-AuAu-collisions-BES-energies-RHIC

Presentation: https://drupal.star.bnl.gov/STAR/system/files/paper_proposal_pwgc-siejka.pdf

The PWGC panel previewed a paper proposal from CF PWG. The panel found that the analysis is mature and should move forward with the proposed target journal, although the estimation of the systematic uncertainties and physics conclusion should be revisited. The following points were discussed.

Slide 16

Q. What is “f_i” and how it was calculated?

A. It is a fraction of residual pairs and from models: vHLLE-UrQMD or Therminator.

C. We know that UrQMD cannot reproduce the data of Lambda/p ratio. 

A. It’s because Lambdas don’t decay in UrQMD model. We implemented afterburner decay and the production gets close to the data.

C. One could use published spectra and estimate the fraction in a data-driven way. It may help to reduce the systematic uncertainty.

Q. Fraction of primary (or residual) pairs is estimated from the model. Did you account for experimental cuts, e.g. |dca|<1cm, which reduces the secondary particles.

A. Same cuts including dca were applied in the model calculations.

Q. How are these plots calculated?

A. p-Lambda CF was calculated based on LL-model with input source sizes shown. The decay kinematics (right-upper plot) was obtained from Therminator model. Using those information, primary p-p decayed from Lambda CF was obtained. (the label is no accurate)

Q. Why you chose 3 R in the right bottom?

A. They correspond to 3 centrality bins.

Slide 23

Q. What’s in residual correction? only from model difference in the fraction or anything else?

A. One from the residual pair fraction and the other from variation of source size as shown as a band in the right bottom plots of slide 16.

Q. The values in this table and plots in slide 24 or 25 gives different impression on the uncertainty, at least by eye. Aye they averaged over all the data? How the total uncertainty was calculated? Are they for extracted radii or CF data points?

A. Yes, they are uncertainties for radii and averaged over centrality, energy, and particle combination. Total uncertainty was calculated by the quadrature sum of each contributions. Each data have different values.

C. Please double-check the consistency between the number in table and uncertainties in the figures. It might be better to have different table, especially the uncertainties are different for energy or particle pairs. 

Slide 24 and 26

Q. Conclusion says discrepancies between identical and nonidentical pairs but e.g. in slide 24, where can we find it?

A. ppbar looks systematically smaller than pp but the models expect similar R.

C. They are consistent within uncertainties. 

C. Please check if there is any correlated error between identical and non-identical pairs. One could take a ratio which can be calculated for all systematic cases, in that way, the correlated uncertainty should be cancelled.

Figure 7

Q. What is centrality for other data?

A. They are mostly for central data.

C. If so, it’s better to compare only with 0-10% data.

Q. Why the other data have smaller uncertainty?

A. They don’t consider residual correction but it’s important and is considered in this analysis.

Q. Do you know what ALICE data look like in terms of R value and systematic uncertainty? They applied the residual correction. Is it similar to what you got?