Search for evidence of Λ3n by observing d+π^- and t+π^- final states in the reaction of 6Li+12C at 2A GeV

The experimental data obtained from the reaction of 6Li projectiles at 2A GeV on a fixed graphite target were analyzed to study the invariant mass distributions of d+π^- and t+π^-. Indications of a signal in the d+π^- and t+π^- invariant mass distributions were observed with significances of 5.3 σ and 5.0 σ, respectively, when including the production target, and 3.7 σ and 5.2 σ, respectively, when excluding the target. The estimated mean values of the invariant mass for d+π^- and t+π^- signal were 2059.3 ± 1.3 ± 1.7 MeV/c2 and 2993.7 ± 1.3 ± 0.6 MeV/c2 respectively. The lifetime estimation of the possible bound states yielding to d+π^- and t+π^- final states were deduced to be as 181-24+30±25 ps and 190-35+47±36 ps, respectively. Those final states may be interpreted as the two-body and three-body decay modes of a neutral bound state of two neutrons and a Λ hyperon, Λ3n.