Importance of Baryon-Baryon Coupling in Hypernuclei

Abstract

The $\Lambda N - \Sigma N$ coupling in $\Lambda$--hypernuclei and $\Lambda \Lambda - \Xi N$ coupling in $\Lambda \Lambda$--hypernuclei produce novel physics not observed in the conventional, nonstrange sector. Effects of $\Lambda \leftrightarrow \Sigma$ conversion in $^3_{\Lambda}$H are reviewed. The role of $\Lambda N - \Sigma N$ coupling suppression in the $A=4,5$ $\Lambda$--hypernuclei due to Pauli blocking is highlighted, and the implications for the structure of $^{10}_{\;\, \Lambda}$B are explored. Suppression of $\Lambda \Lambda - \Xi N$ conversion in $^{\;\;\, 6}_{\Lambda \Lambda}$He is hypothesized as the reason that the $< V_{\Lambda \Lambda} >$ matrix element is small. Measurement of $^{\;\;\, 4}_{\Lambda \Lambda}$H is proposed to investigate the full $\Lambda \Lambda - \Xi N$ interaction. The implication for $\Lambda \Lambda$ analog states is discussed.Comment: 17 pages LATEX, 1 figure uuencoded postscrip

Hyperon–nucleon interaction within chiral effective field theory revisited

“…10 (c). Then the contribution of, say, the transition ΛN → ΣN → ΛN to the effective two-body potential is reduced as compared to the situation in free space because the propagator includes now the kinetic energy of the spectator nucleons and, as a consequence, the effective interaction is less attractive [27,60]. At the same time, the equal treatment of the Λ and Σ hyperons in the two-and few-body equations generates contributions of the form shown in Fig.…”

“…The anomalously small binding energy of this state has been notoriously difficult to describe in past calculations [66]. Among other things, a strong suppression of the ΛN -ΣN coupling is seen as one possible explanation [60,67]. Thus, one would expect noticeable differences between the predictions of the two EFT interactions.…”

“…In former studies of hyperonic few-body systems, the role of the spin-dependence of the ΛN potential for the binding energies of s-shell hypernuclei has been discussed in terms of the appropriately averaged effective ΛN interaction [58][59][60]. We will do the same here.…”

Hyperonic mixing in five-baryon double-strangeness hypernuclei in a two-channel treatment

“…The probability of the rare π + channel of hypernuclear weak decay is sensitive to Σ + admixture [10,11]. The coupling can lead in some cases to the reverse order of spin doublet levels [12]. Also production of neutronrich Λ hypernuclei from (K − , π + ) and (π − , K + ) reactions can proceed via Σ − admixture as a doorway state [13].…”

Calculation of theHΣ4eBound State in theHHarada1 1998Phys. Rev. Lett.615680View full textAdd to dashboardCite

“…[8,9]. The coupling is expected to be one of the key elements for solving the anomalous binding energies of 4 L He, 4 L H, and 5 L He [10,11].…”