E(1420) meson as aKK¯π molecule

In this article an experimental summary of the E(1420) meson with ${\mathit{J}}^{\mathit{P}\mathit{C}}$=$1^{++}$ is presented and it is argued that the E(1420) is not explained by QCD in terms of being a fundamental arrangement of quarks and gluons. We then develop a final-state rescattering mechanism based on one-particle-exchange Born terms. We sum these Born terms through a Fredholm integral equation and obtain a Fredholm determinant which shows an enhancement at the E(1420) with ${\mathit{J}}^{\mathit{P}\mathit{C}}$=$1^{++}$. The subsequent sum of Born terms is analogous to a π orbiting in a p wave around an s-wave KK¯ system. This represents the first example of a molecular state which is bound by color-singlet particle exchanges, as opposed to work by Weinstein and Isgur, which uses color forces to bind their molecule. A phenomenological analysis of all the latest KK¯π data arising from hadroproduction argues that the molecular picture for the E(1420) is consistent. We show that if the molecular nature for the E(1420) is generated by the above final-state Born terms, an exotic ${\mathit{K}}^{+}$K${\mathrm{¯}}_0$ ${\mathit{K}}^{+}$ ${\mathit{J}}^{\mathit{P}}$=$0^{\mathrm{-}}$ molecule must exist at the KK¯K threshold.