Field theoretic study of light hypernuclei

A nonperturbative field theoretic calculation has been made for the $s$-shell hypernuclei. Here we dress the $\Lambda$- and $\Sigma$- hypernuclei with off-mass shell pion pairs. The analysis replaces the scalar isoscalar potential by quantum coherent states. The binding energies of $^{4+n\Lambda}$He $(n=0,1,2)$ agree quite well with the RMF result of Greiner. The experimental binding energies of $^4$He and $^3$He are reasonably well reproduced in our calculation. A satisfactory description of the relevant experimental $\Lambda$- and $\Sigma$- separation energies has been obtained.