Alpha-particle condensation in light hypernuclei

Gas-like α-cluster states are investigated in light Λ hypernuclei. The α condensate-type microscopic cluster model wave function is introduced to describe Λ hypernuclei. In particular, the analogous state to the famous Hoyle state, the second image state in 12C, is investigated in 13ΛC, with the use of the new type wave function. The Hoyle state is known to have a gas-like 3α cluster structure, where the 3α particles are condensed into an identical S orbit. The second image state in 13ΛC is shown to have the image structure. A strong shrinkage effect by adding the Λ particle is seen for the state, reducing the rms radius from 3.8 fm in the Hoyle state to 2.8 fm. In spite of the shrinkage effect, the α condensate fraction of about 60% still survives, though it is reduced by about 20% from the Hoyle state.