Formation and lifetime measurements of light hypernuclei in Ag+Ag collisions at sNN = 2.55 GeV
Abstract
We present the first observation of 3 H and 4 H in Ag+Ag collisions at sNN = 2.55 GeV, emitted around mid-rapidity. The hypernuclei are reconstructed via their two-body decay channels and identified through their weak-decay topology, employing an artificial neural network for enhanced discrimination. The analysis methodology is validated using hyperons. The resulting rapidity distributions, dN/dy, exhibit a bell shape centered at mid-rapidity. The yield of 4 H is equal to or exceeds that of 3 H, which contrasts the measurement from the STAR collaboration at sNN = 3 GeV and is consistent with a scenario in which hypernuclei receive feed-down from excited states. The data enable a high-precision measurement of the hypernuclei lifetimes. For the 3 H, a lifetime of τ3 H = (239 23(stat) 18(sys))\,ps, is extracted, consistent on the 1σ level with that of the free . In contrast, the 4 H lifetime of τ4 H = (209 7(stat) 10(sys))\,ps, shows a 4.5 σ deviation from the free lifetime. The results consolidate the available world data.
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