Title: Hypernuclear decay of strangeness -2 hypernuclei
Abstract: Decay of S = -2 hypernuclei: Weak and strong baryon-baryon-meson verticesJordi ManeuThe study of the decay of hypernuclear systems gives us a very valuable information on the strong and weak interaction between hyperons and nucleons.These exotic systems decay mainly through two-body mechanisms, involving one or two hyperons (ΛN or ΛΛ) in the initial state and none or one hyperon (Y ) in the final state (NN or Y N).One-meson-exchange models can give us a theoretical description of the elementary reaction, requiring the knowledge of strong and weak baryon-baryon-meson (BBM) couplings.While the vertices for the ΛN → NN were already derived a few years ago [1,2] in the context of the decay of single-Λ hypernuclei, the ones involving an initial ΛΛ pair were only derived for the direct ΛΛ → Y N weak transition [3,4,5,6], participating in the decay of strangeness -2 systems.The consideration of the strong interaction between the baryons in the initial pair (ΛΛ -ΞN -ΣΣ) leads to additional weak two-body transitions, starting from either a ΞN pair or a ΣΣ one, and therefore requires the explicit calculation of new strong and weak vertices.The main objective of this work is to present the relevant vertices for theIn a meson exchange picture, every ΛΛ → Y N transition can be understood in terms of the exchange of mesons between the interacting baryons, with masses related to the inverse of the interaction range and with quantum numbers allowed by the symmetries governing the underlying dynamics.Within this model, a reaction can be understood as a product of two contributions: a strong vertex and a weak one, where the strangeness variation occurs, connected through the meson propagator.While the calculation for the exchange of pseudoscalar mesons other than the pion requires the use of SU(3) f symmetry, the inclusion of vector mesons in the formalism requires the use of SU(6) = SU(2) s × SU(3) f spin-flavour symmetry (SU(6) W for the weak vertices), as will be explained further below. PoS(CD15)129Decay of S = -2 hypernuclei: Weak and strong baryon-baryon-meson vertices Jordi Maneu