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Title: Measurements of hypernuclei production and hyper-to-light nuclei ratios in Au+Au √s_NN = 3 GeV collisions
PAs: Xin Dong, Xionghong He, Chenlu Hu, Yuanjing Ji, Yue Hang Leung, Xiujun Li, Nu Xu, Fengyi Zhao, Yapeng Zhang, Yifei Zhang
Target journal: Physics Letter B

Bookmarks: Abstract Figures Supplemental materials Paper draft Note

Abstract:

We report the measurements of hypernuclei production in Au+Au √s_NN = 3 GeV collisions. Hypertriton are reconstructed via both 2-body and 3-body mesonic decay channels. Precise measurements on hypertriton branching ratio R3 are reported. Light-to-hyper nuclei yield ratios as well as strangeness population factor S_A (A=3, 4) are also reported as a function of momentum and rapidty in 0-10% and 10-40% centralities. No kinematic and centrality dependence of S_A is observed within uncertainties. This phenomena provide evidence that coalescence parameter BA of light and hyper nuclei follow similar tendency versus pT, rapidity and centrality.

Proposed figures:

Figure 1:

Figure 1: (a)The reconstructed invariant mass distribution of H3L via H3L→pdπ^-. Black solid circles are the reconstructed hypertriton candidates from the same event. The uncorrelated combinatorial backgrounds (open circles) are reconstructed by the mix-event method. Both uncorrelated (dpπ) triplets (dotted line) and Λd (dashed line) contribute to the uncorrelated combinatorial backgrounds. (b) An example of template fit to the topological distribution of dpπ triplets after subtracting mix-event backgrounds in 2.989<Mass(dpπ)<2.995 GeV/c. Two templates built from full detector simulations, Λd (gray shadow) and H3L (magenta shadow), are used to fit the data (blue solid circles). (c) Blue solid circles are the invariant mass distribution of H3L candidates after subtracting uncorrelated mixe-event backgrounds. Besides H3L (magenta shadow), correlated Λd (primary Λ, gray shadow) and Λd(Ξ→Λ, green shadow) will also enhance the invariant mass distribution of (dpπ) triplets around H3L mass region. The residual backgrounds (brawn dashed lines) are fitted by linear function.

Figure 2:

Figure 2: Complementary to binding energy measurements, H3L R₃=(B.R.(H3L→³He π^- ))/(B.R.(H3L→pdπ^- )+B.R.(H3L→³Heπ^- )) would provide additional constrains on Y-N interaction strength. New measurements on H3L R₃ from STAR are presented. The uncertainties from this measurement are much improved compared with helium chamber measurements and STAR previous measurements.

Figure 3:

Figure 3: The hyper-to-light nuclei yield ratios H3L/³He (Blue),H4L/⁴He (Magenta) as well as yield ratios (Black) are shown as a function of rapidity in 0-10% and 10-40% centralities.

Figure 4:

Figure 4: Strangeness population factor SA is defined as hyper-to-light nuclei yield ratios over Λ/p yield ratios: S_A=^A_ΛH/(^AHe×Λ/p). This plot shows S3 (Blue) and S4 (Magenta) shown as a function of pT/A in 3 rapidity bins in 0-10% and 10-40% centralities.

Figure 5:

Figure 5: This plot shows S3 (Blue) and S4 (Magenta) at pT/A>0.4 GeV/c as a function of rapidity in 0-10% and 10-40% centralities.

Conclusions:

Production of hypertriton are measured via both 2-body and 3-body decay channel, and branching ratio R₃ are reported.
Suppression of ³_ΛH/³He yield ratios compared to that of Λ/p is observed at both 0-10% and 10-40% centrality in Au+Au collisions at 3 GeV. The ⁴_ΛH/⁴He yield ratios are comparable to that of Λ/p, which is possibly due to feed-down contributions from exited state that enhances ⁴_ΛH production.
No obvious kinematic and centrality dependence of S_A is observed at 3 GeV. This phenomena give evidence that coalescence parameter BA of light and hyper nuclei follow similar tendency versus p_T, rapidity and centrality.

Analysis notes:

Paper draft:

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Paper proposal: Measurements of hypernuclei production and hyper-to-light nuclei ratios in Au+Au $\snn=3$ GeV collisions