Combining heavy quark spin and local hidden gauge symmetries in the dynamical generation of hidden charm baryons

Abstract

We present a coupled channel unitary approach to obtain states dynamically generated from the meson-baryon interaction with hidden charm, using constraints of heavy quark spin symmetry. As a basis of states, we use D̄B, D ̄*B states, with B baryon charmed states belonging to the 20 representations of SU(4) with JP=1/2+, 3/2 +. In addition we also include the ηcN and J/ψN states. The inclusion of these coupled channels is demanded by heavy quark spin symmetry, since in the large mQ limit the D and D* states are degenerate and are obtained from each other by means of a spin rotation, under which QCD is invariant. The novelty in the work is that we use dynamics from the extrapolation of the local hidden gauge model to SU(4), and we show that this dynamics fully respects the constraints of heavy quark spin symmetry. With the full space of states demanded by the heavy quark spin symmetry and the dynamics of the local hidden gauge, we look for states dynamically generated and find four basic states that are bound, corresponding to D̄Σc, D̄Σc*, D̄*Σc, and D̄*Σc*, decaying mostly into ηcN and J/ψN. All the states appear in isospin I=1/2, and we find no bound states or resonances in I=3/2. The D̄Σc state appears in J=1/2 and the D̄Σc* in J=3/2; the D̄*Σc appears nearly degenerate in J=1/2, 3/2 and the D̄*Σc* appears nearly degenerate in J=1/2, 3/2, 5/2, with the peculiarity that in J=5/2 the state has zero width in the space of states chosen. All the states are bound with about 50 MeV with respect to the corresponding D̄B thresholds, and the width, except for the J=5/2 state, is also of the same order of magnitude. Finally, we discuss the uncertainties stemming from the expected breaking of SU(4) and the heavy quark spin symmetry. © 2013 American Physical Society.