Shedding light on Hexaquarks

Abstract

Several new findings in the four, five and six quark systems reheat the interest in the field of multiquark states (beyond trivial qq¯and qqq). A lot of progress has recently been made in the 6q sector, on both the theoretical and experimental side. A resonance like structure observed in double-pionic fusion to the deuteron, at M = 2.38 GeV with Γ =70 MeV and I(J P ) = 0(3 + ) has been consistently observed in a wealth of reaction channels, supporting the existence of a resonant dibaryon state -the d * (2380). These studies include measurement of all the principle strong decay channels in pn collisions in the quasi-free mode by the WASA-at-COSY and HADES collaborations. The internal structure of the d * (2380) is largely unknown. It can contain various hidden color 6q configurations, ∆∆ molecular states with angular momentum L=0,2,4,6 as well as meson-assisted dressed dibaryon structures. The large set of experimental data obtained to date gives some constraints on the internal structure of the d * (2380) dibaryon, but does not settle the issue. The d * is the only multiquark state which can be produced copiously at current facilities, offering unique access to information beyond its basic quantum numbers, particularly its physical size and internal structure.