Search for $^6_Lambda$H hypernucleus by the $^6$Li$(pi^-,K^+)$ reaction at $p_{pi^-}$ = 1.2 GeV/$c$

We have carried out an experiment to search for a neutron-rich hypernucleus, $^6_{Lambda}$H, by the $^6$Li($pi^-,K^+$) reaction at $p_{pi^-}$ =1.2 GeV/$c$. The obtained missing mass spectrum with an estimated energy resolution of 3.2 MeV (FWHM) showed no peak structure corresponding to the $^6_{Lambda}$H hypernucleus neither below nor above the $^4_{Lambda}$H$+2n$ particle decay threshold. An upper limit of the production cross section for the bound $^6_{Lambda}$H hypernucleus was estimated to be 1.2 nb/sr at 90% confidence level.