Case for quasinuclearN¯Nbound states

Abstract

Recent experimental results on nucleon-antinucleon annihilation reactions of the type NN~~X have provided evidence for a new mesonic state X2 with quantum numbers J (I ) =2++ (0+ ) which lies outside of the usual quark-antiquark (QQ) tensor meson nonet of liavor SU(3). We show that the observed production rates of X2 from atomic pp states of orbital angular momentum L =0, 1, as well as the decay characteristics of X"namely, its preference for pp over~~decay and the absence of an observable KK mode, are consistent with an interpretation of X2 as a quasinuclear bound state of the NN potential. The principal binding mechanism for such states is provided by the coherent tensor forces for isospin I =0 which arise from meson exchanges. We review the evidence for the 0++(0+) and 1 (0 ) states predicted in this model and apply the 'Po strongcoupling quark model to estimate the decay branching ratios for a variety of NN bound states. Key experimental tests of our interpretation are discussed.

A new state of baryonium

“…Also, there have been many indications that in the nucleon-antinucleon system, there should be a strong attractive NN bound state near threshold [12,13]. This understanding evolved to attribute the long force to be that of pion exchanges and the repulsive short-range interaction to that of ω exchange [14].…”

Hadron spectroscopy with antiprotons

“…A glance at Figure 1 shows that the 13P2 multiplet is already complete and hence f2( 1520) must be exotic. Its most likely nature is a multiquark meson or a deeply bound" state (7). Figure 2b shows the qq mass spectrum for pp annihilation at rest into n"qq (8).…”

Metastable Exotic Multihypernuclear Objects

“…Furthermore, the Strangeness content of this strange nucleus is f, = S / A = 1. The formation of such novel, exotic states of nuclear matter in heavy-ion collisions [42] is an intriguing possibility; the production Cross section, however, will be very small. We are presently investigating this problem quantitatively based on a covariant coalescence model, using the microscopic baryon distribution from the relativistic quantum molecular-dynamics model as input [43].…”