Hybrid and conventional baryons in the flux-tube model

Conventional and hybrid light quark baryons are constructed in the nonrelativistic flux-tube model of Isgur and Paton, which is motivated by lattice QCD. The motion of the flux tube with the three quark positions fixed, except for center-of-mass corrections, is discussed. It is shown that the problem can be reduced to the independent motion of the junction and the strings connecting the junction to the quarks. The important role played by quark-exchange symmetry in constraining the flavor structure of (hybrid) baryons is emphasized. The flavor, quark spin S, and J(P) of the seven low-lying hybrid baryons are found to be (N,Delta)(2S+1)J(P)=N-2 1/2(+), N-2 3/2(+), Delta(4) 1/2(+), Delta(4) 3/2(+), Delta(4) 5/2(+), where the N-2 1/2(+) and N-2 3/2+ states are doublets. The motion of the three quarks in an adiabatic potential derived from the flux-tube dynamics is considered. A mass of 1870+/-100 MeV for the lightest nucleon hybrids is found by employing a variational method.