Paper Title: Light- and Hyper-Nuclei Directed Flow in Au+Au Collisions in √sNN = 3.0 - 4.5 GeV at RHIC
PAs: Chengdong Han, Junyi Han, Xionghong He, Chenlu Hu, Yaping Wang, Nu Xu, Yue Xu, Yapeng Zhang
PA representative: Chengdong Han
Target journal: Phys. Rev. Lett.
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Abstract:
We report the first results on collision energy and particle mass dependence of directed flow v1 of light-nuclei (p, d, t, 3He, 4He)
and hyper-nuclei (3ΛH, 4ΛH) in mid-central Au+Au collisions at center of mass energy √sNN = 3.0, 3.2, 3.5, 3.9 and 4.5 GeV.
All data have been collected by the STAR experiment in the fixed-target mode during the second phase of the RHIC beam energy scan.
The mid-rapidity v1 slope, dv1/dy|y=0, of hyper-nuclei shows a similar energy and particle mass dependence to that of light-nuclei.
Calculations of hadronic transport model plus coalescence afterburner qualitatively reproduced the observed dependences.
These results suggest that the coalescence mechanism plays a dominant role in the formation of light-and hyper-nuclei in these heavy ion collisions.
Paper figures:
FIG. 1. Topologically reconstructed (2-body decay) 3ΛH (left panel), (3-body decay) 3Λ H (middle panel) and 4Λ H (right panel) from 3.2, 3.5, 3.9 and 4.5 GeV Au+Au collisions. Back- ground subtracted distributions are shown as red symbols. The significances of the mass peaks are also indicated in the figure.
FIG. 2. Light- and hyper-nuclei directed flow v1 shown as a function of particle rapidity from 3.2, 3.5, 3.9 and 4.5 GeV mid-central (5-40%) Au + Au collisions.
The rapidity dependence of Λ v1 is shown in left column. 3ΛH, with both 2-body and 3-body decays, and 4ΛH rapidity dependence are shown in the middle and
right column, respectively. The results of the fit are shown as the red-yellow lines. For comparison, the rapidity dependence for p, d, t, 3He, and 4He are shown
as open markers and the linear terms of the fitting results for these lightnuclei are displayed as dashed lines in the positive rapidity region.
FIG. 3. Particle mass dependence of the mid-rapidity v1 slope for hypernuclei (left plot) and lightnuclei (right plot) from mid-central 5-40% Au + Au collisions.
The results from the 3 GeV data is taken from Phys. Rev. Lett. 130, 212301 (2023). Transport model JAM + coalescence results are shown as colored bands.
FIG. 4. Collision energy dependence of the mid-rapidity v1 slope for hypernuclei (left plot) and lightnuclei (right plot) from mid-central 5-40% Au + Au collisions. The results from the 3 GeV data is taken from Phys. Rev. Lett. 130, 212301 (2023). Transport model JAM + coalescence results are shown as colored bands.
Conclusions:
In this letter, we report the collision energy and particle mass dependence of the directed flow $v_{1}$ for both light- and hyper-nuclei in $\sqrt{s_{NN}}$ = 3.0,
3.2, 3.5, 3.9 and 4.5 GeV Au + Au collisions measured by the STAR experiment at RHIC. An approximate atomic mass number scaling and energy dependence are
observed in the measured $v_{1}$ slopes of light- and hyper-nuclei at mid-rapidity. Calculations of hadronic transport model plus coalescence afterburner qualitatively
reproduced the observed dependences for hyper-nuclei as well as light-nuclei implying coalescence process dominate the underlying production mechanism for those light clusters.
%It suggests that the dominant process in the production mechanism for light clusters is the coalescence process. In addition, the distribution of particle mass and collision energy dependence of the mass scaled Mid-rapidity $v_{1}$ slope of light- and hyper-nuclei shows that as the collision energy increases, the baryon number scale breaks down,
indicating that the coalescence process dominates the production mechanism of light clusters becoming weaker.
Moreover, results from a high statistics 2 billion event samples for the 3.0 GeV Au + Au collisions in the next will significantly enhance the precision
and help constrain coalescence parameters, as well as constrain $N$-$N$ and $Y$-$N$ interactions for both light- and hyper-nuclei at the high densit
Presentations:
FCV-PWG meeting:
https://drupal.star.bnl.gov/STAR/system/files/Paper_proposal_Lightnuclei_hypernuclei_collectivity_3.0_3.9GeV_ChengdongHan.pdf
https://drupal.star.bnl.gov/STAR/system/files/Updated_paper_proposal_Paper_proposal_Lightnuclei_hypernuclei_v1_ChengdongHan.pdf
https://drupal.star.bnl.gov/STAR/system/files/20240513.pdf
https://drupal.star.bnl.gov/STAR/system/files/Chengdong_Han_preliminary_figures%20request_20230809.pdf
https://drupal.star.bnl.gov/STAR/system/files/20230817.pdf
https://drupal.star.bnl.gov/STAR/system/files/ChengdongHan_PWG_20230726.pdf
https://drupal.star.bnl.gov/STAR/system/files/ChengdongHan_FCV_PWG_20230329.pdf
https://drupal.star.bnl.gov/STAR/system/files/CDHan_20230322_v1_of_H4L_and_H3L.pdf
https://drupal.star.bnl.gov/STAR/system/files/Directed_flow_of_H4L_and_H3L_lambda_decay%20in_3.2GeV%20-%20v2.pdf
https://drupal.star.bnl.gov/STAR/system/files/CHan_PWG_20220427_Directed_flow_of_H4L_and_H3L_2-body_decay%20in_3.2GeV.pdf
https://drupal.star.bnl.gov/STAR/system/files/3p5_HN_FCV_0.pdf
https://drupal.star.bnl.gov/STAR/blog/yuexu/LightNucleiFlowpwg20230111
https://drupal.star.bnl.gov/STAR/system/files/LightNucleiFlowWithEfficiency_Yue20231129.pdf
https://drupal.star.bnl.gov/STAR/system/files/v1_Cross_Check_with_Sharang_Ding.pdf
QM 2023:
https://drupal.star.bnl.gov/STAR/system/files/ChengdongHan_PWG_20230726.pdf
SQM 2024:
https://drupal.star.bnl.gov/STAR/system/files/ChengdongHan_PWG_20230726.pdf
STAR Pre-QM2023 Meeting:
https://drupal.star.bnl.gov/STAR/system/files/ChengdongHan_QM2023_report_v4.pdf
STAR Analysis Meeting and BES-II Workshop:
https://drupal.star.bnl.gov/STAR/system/files/ChengdongHan_STAR%20Analysys%20meeting%20and%20BES-II%20workshop%20towards%20QM23_20230628.pdf
https://drupal.star.bnl.gov/STAR/system/files/20230628_Workshop.pdf
STAR Collaboration Meeting:
https://drupal.star.bnl.gov/STAR/system/files/CDHan_20220914_v1_v2_of_H4L_and_H3L_lambda_decay%20in_3.2GeV_0.pdf
https://drupal.star.bnl.gov/STAR/system/files/3p5_HN_0913.pdf
https://drupal.star.bnl.gov/STAR/system/files/20230301_Collaboration_Meeting.pdf
