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Paper proposal: Non-identical particle femtoscopy measurements in the STAR Beam Energy Scan program

Updated on Sun, 2024-03-24 09:21. Originally created by pawszy on 2022-09-13 07:47.

Title: Non-identical particle femtoscopy measurements in the STAR Beam Energy Scan program

PA: Diana Pawłowska, Sebastian Siejka, Paweł Szymański, Daniel Wielanek, Hanna Zbroszczyk

Abstract: 

The femtoscopy method can probe the space-time structure and dynamics of strongly interacting nuclear matter created in high-energy collisions. The correlation of two non-identical particles allows one to extract information about asymmetry in the emission process between two kinds of particles. Such asymmetry arises in a system with a strong radial flow. In this work, femtoscopic analysis of three different systems (pion-kaon, pion-proton, and kaon-proton) in central (0-10\%) Au+Au collisions at $\sqrt{s_{NN}} = 39$ GeV is reported. Source sizes are consistent between different sign combinations and larger in the case of pion-kaon and pion-proton than for kaon-proton pairs. Obtained asymmetries show that lighter particles, on average, are emitted closer to the center of the source and/or later than heavier particles. Additionally, the pion-kaon correlations are analyzed in the centrality dependence in Au+Au collisions at $\sqrt{s_{NN}} = 39$ GeV and for three energies of the Beam Energy Scan program $\sqrt{s_{NN}} = 7.7$, $11.5$, and $39$ GeV. The sizes of pion-kaon sources increase with increasing centrality and energy. These results confirm that collective behavior exists in the lower energies of the BES-I program.

Paper draft:

Analysis Note:

Presentation: 
 

Results (Proposed figures):

Figure 1



Comparison of $C_0^0 (k^*)$ (left) and $\Re C_1^1 (k^*)$ (right) SH components of like-sign (bottom) and unlike-sign (top) $\pi K$ pairs for Au+Au collisions at $\sqrt{s_{NN}} = 39$ GeV in different (0-10\%, 10-30\% \& 30-70\%) centrality classes. Lines represent theoretical fits calculated using CorrFit software [1]. Errors are statistical only.

Figure 2

Comparison of $C_0^0 (k^*)$ (left) and $\Re C_1^1 (k^*)$ (right) SH components of like-sign (bottom) and unlike-sign (top) $\pi K$ pairs for central(0-10\%) Au+Au collisions at different energies $\sqrt{s_{NN}} = 7.7$, $11.5$ \& $39$ GeV. Lines represent theoretical fits calculated using CorrFit software [1]. Errors are statistical only.

Figure 3

Comparison of $C_0^0 (k^*)$ (left) and $\Re C_1^1 (k^*)$ (right) SH components of like-sign (bottom) and unlike-sign (top) for pion-kaon, pion-proton and kaon-proton pairs for central(0-10\%) Au+Au collisions at $\sqrt{s_{NN}} = 39$ GeV. Lines represent theoretical fits calculated using CorrFit software [1]. Errors are statistical only.


Figure 4



Centrality dependence of pion-kaon source size (R) for Au+Au collisions at $\sqrt{s_{NN}}$ = 39 GeV.

Figure 5



Centrality dependence of pion-kaon emission asymmetry ($\mu$) for Au+Au collisions at $\sqrt{s_{NN}}$ = 39 GeV.

Figure 6

Energy dependence of pion-kaon source size (R) for 0-10\% most central Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5 and 39 GeV.


Figure 7

Energy dependence of pion-kaon emission asymmetry ($\mu$) for 0-10\% most central Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5 and 39 GeV.

Figure 8

Mean pair transverse mass dependence of source size for central (0-10\%) Au+Au collisions at $\sqrt{s_{NN}}$ = 39 GeV for different charge combinations of pion-kaon, pion-proton, and kaon-proton pairs.

Figure 9

Mean pair transverse mass dependence of emission asymmetry for central (0-10\%) Au+Au collisions at $\sqrt{s_{NN}} = 39$ GeV for different charge combinations of pion-kaon, pion-proton, and kaon-proton pairs.


Figure 10

  

Comparison of the relation between emission asymmetry of $\pi K$, $\pi p$, and $K p$ pairs for different charge combinations.


Figure 11

Model (Therminator 2 and UrQMD) predictions for $\pi^+ K^+$ correlation functions. UrQMD and experimental functions correspond to 0-10\% and Therminator 2 to 0-5\% central Au+Au collisions at $\sqrt{s_{NN}}$ = 39 GeV.

Figure 12


Model (Therminator 2 and UrQMD) predictions for $\pi^- K^+$ correlation functions. UrQMD and experimental functions correspond to 0-10\% and Therminator 2 to 0-5\% central Au+Au collisions at $\sqrt{s_{NN}}$ = 39 GeV.

Figure 13

Comparison of correlation functions from Therminator 2 model for primary and all $\pi^+ K^+$ pairs for Au+Au collisions at $\sqrt{s_{NN}}$ = 39 GeV in 0-5\% centrality class.

Figure 14


Comparison of correlation functions from UrQMD model for primary and all $\pi^+ K^+$ pairs for Au+Au collisions at $\sqrt{s_{NN}}$ = 39 GeV in 0-10\% centrality class.

 


Conclusions:

  • Results indicate that the average space-time positions of pions and kaons (and also pions and protons) are not the same for Au+Au collisions at 7.7, 11.5, and 39 GeV.
  • Very small asymmetry is present in the case of kaon-proton pairs.
  • Measured asymmetry satisfies the predicted relationship:
     
  • Values of source parameters are consistent for all charge combinations.
  • Spherical harmonics components are well described using 3-dimensional Gauss distribution as the source function.
  • Strong interaction between kaons and protons needs investigation.




 

Previous presentations:

 

Bibliography:

[1] Kisiel, A., "CorrFit - A program to fit arbitrary two-particle correlation functions,", Nukleonika 49, 81-83 (2004).
 

 

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