Paper Title:  Energy dependence of Kaon correlation function 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

 Abstract: 
 We present the K^{+} - K^{+}, K_{s}^{0} - K_{s}^{0} femtoscopic correlations in Au + Au fixed-targed collisions at sqrt{s_{NN}} = 3.0, 3.2, 3.5, 3.9 and 4.5 GeV from STAR. Extracted invariant radius r_{G} and correlation strength \lambda are consistent between charged Kaon and neutral kaon. There is no clear energy dependence observed. The abundance asymmetry of K^{0} - \bar{K}^{0} extracted by K_{s}^{0} - K_{s}^{0} pair correlation function The K^{0} - \bar{K}^{0} asymmetry decrease with collision energy increasing. UrQMD calculations qualitatively describe results.

Figure 1:

Fig. 1: Panel (a) shows the invariant mass distribution of K_{s}^{0} from the combination pair of \pi^{+} and \pi^{-}. Blue circles are the background distribution constructed by rotating momentum vectors of daughter pions. Panel (b) is the square of mass distribution extracted from the time-of-flight (TOF) detector. Results of the fitting are shown by red line while the vertical blue dashed lines indicate the signal region.

Figure 2:




Fig. 2: K_{s}^{0} (upper panels) and K^{+} (lower panels) acceptances are shown as p_{T} vs. rapidity from \sqrt{s_{NN}} = 3.0, 3.2, 3.5, 3.9 and 4.5 GeV Au + Au collisions. Dashed red boxes indicate the acceptance region used in the kaon correlation function analysis. In the lower panels, the long dashed black lines show the momentum cuts in the STAR TPC, which limits the charged kaon acceptance at mid-rapidity.

Figure 3:

Fig. 3: Solid circles are the measured K_{s}^{0} - K_{s}^{0} (upper panels) and K^{+} - K^{+} (lower panel) one-dimension correlation functions from \sqrt{s_{NN}} = 3.0, 3.2, 3.5, 3.9 and 4.5 GeV Au + Au collisions at 0-60% centrality. Vertical lines and open boxes represent the statistical and systematic uncertainties, respectively. Open circles show the Kaon correlation function with the effect of only quantum statistics, and the results of a Gaussian source to the correlation function are shown by the dashed lines. The green bands are Kaon correlation functions from transport model UrQMD plus a correlation package CRAB.

Figure 4:

Fig. 4: Energy dependence of the extracted Gaussian source parameters r_{G} (a), correlation strength \lambda (b) and Kaon - anti-Kaon asymmetry (c) for K^{+} - K^{-} [1] (open circle) and K^{0} - \bar{K}^{0} (solid circle). Panel (d) shows the r_{G} as function as <m_{T}>. For comparison, on-dimension Gaussian source parameters from pion correlation functions are shown in panel (a), (b) and (c) as squares. Results from transport model UrQMD are shown as dashed lines.

Summary:

1. K_{s}^{0} and K^{+} source size and correlation strangth are consistent, pion source size are larger then kaons.
2. No clear energy dependence of pion, K_{s}^{0} and K^{+} particle emission source, and consistent with UrQMD model.
3. The abundance asymmetry of K^{0} and \bar{K}^{0} extracted. The asymmetry decrease depending on the energy increasing, and consistent with UrQMD model.

presentation links:
K_{s}^{0}:
https://drupal.star.bnl.gov/STAR/system/files/20220721CFPWG_LiAngZhang.pdf
https://drupal.star.bnl.gov/STAR/system/files/20220913_LiAngZhang_FXTK0sK0sCF.pdf
https://drupal.star.bnl.gov/STAR/system/files/20230301LiAngUpdateAndPaperProposal_v3.pdf
https://drupal.star.bnl.gov/STAR/system/files/20230425LiAngK0s-K0sCFUpdate.pdf
https://drupal.star.bnl.gov/STAR/system/files/20230629STARBESIIWorkshop_LiAngZhang_BijunFan.pdf
https://drupal.star.bnl.gov/STAR/system/files/20230803LiAngK0s-K0sCFUpdate.pdf
https://drupal.star.bnl.gov/STAR/system/files/K0sK0sCFUpdates_LiAngZhang_PreliminaryRequest.pdf
https://drupal.star.bnl.gov/STAR/system/files/K0sK0sA0F0Par_LiAngZhang.pdf

K^{+}:
https://drupal.star.bnl.gov/STAR/system/files/K_CF_0.pdf
https://drupal.star.bnl.gov/STAR/system/files/sys_K_CF_6.pdf
https://drupal.star.bnl.gov/STAR/system/files/KK_CF_3GeV_0.pdf
https://drupal.star.bnl.gov/STAR/system/files/collaboration%20meeting_0.pdf
https://drupal.star.bnl.gov/STAR/system/files/KK_CF_FXT_3p85_Collabration_meeting_bijunFan.pdf
https://drupal.star.bnl.gov/STAR/system/files/KK_3p2GeV_CF_0525_pwg.pdf
https://drupal.star.bnl.gov/STAR/system/files/deltaphistar_3p2_KK.pdf
https://drupal.star.bnl.gov/STAR/system/files/preliminary_request_3p2_KK_230601_0.pdf
https://drupal.star.bnl.gov/STAR/system/files/Preliminary_request_KK_HBT_3p2to3p9_Bijun_230810_v2.pdf
https://drupal.star.bnl.gov/STAR/system/files/Collabration_meeting_KK_HBT_FXT_Bijun_231017sss.pdf
https://drupal.star.bnl.gov/STAR/system/files/Charged_Kaon_HBT_STAR_FXT_with_eTOF_0111.pdf