A meson-baryon molecular interpretation for some $\Omega_{c}$ Ω c excited states

Abstract

We explore the possibility that some of the five narrow Ωc resonances recently observed at LHCb could correspond to pentaquark states, structured as meson-baryon bound states or molecules. The interaction of the low-lying pseudoscalar mesons with the ground-state baryons in the charm +1, strangeness −2 and isospin 0 sector is built from t-channel vector meson exchange, using effective Lagrangians. The resulting s-wave coupled-channel unitarized amplitudes show the presence of two structures with similar masses and widths to those of the observed Ωc(3050) 0 and Ωc(3090) 0 . The identification of these resonances with the meson-baryon bound states found in this work would also imply assigning the values 1/2 − for their spin-parity. An experimental determination of the spin-parity of the Ωc(3090) 0 would help in disentangling its structure, as the quark-based models predict its spin-parity to be either 3/2 − or 5/2 − .

The Molecular Nature of Some $$\varOmega _c^0$$ States

“…Several other works [17,18,19,20] have also addressed the possibility of interpreting of some of the Ω c states seen at CERN as quasi-bound meson-baryon systems, as well as the prediction of analogous states in the bottom sector [21], finding results which are similar to those of our work [16] and hinting that the meson-baryon description cannot be ignored when trying to understand the nature of these excited heavy baryons.…”

“…The G l function for the meson-baryon loop is regularized using the dimensional regularization approach, which introduces the dependence on a subtraction constant a l (µ) for each intermediate channel l at a given regularization scale µ (see Eq. (18) in [16]).…”

“…Some works suggest a css quark description within revisited quark models [2,3,4,5,6,7,8,9] while others propose a pentaquark interpretation [10,11,12]. Models that can describe some resonances as quasi-bound states of an interacting meson-baryon pair [13,14,15] offer a complementary scenario, an approach that we have re-examined in [16] in view of the new experimental data. It is plausible to expect that some excitations in the C = 1, S = −2 sector can be obtained by adding a uū pair to the natural css content of the Ω 0 c , just as a pentaquark structure with a cc pair is more natural to explain the P c (4380) and P c (4450) excited nucleon resonances than an extremely high energy excitation of the three quark system.…”

$\Omega_c$ excited states with heavy-quark spin symmetry

“…[7] two Ω c resonant states at 3050 MeV and 3090 MeV were generated with spin-parity J P = 1/2 − , reproducing two of the experimental states. Also, within an extended local hidden gauge approach that incorporates low-lying 1/2 + and 3/2 + baryons together with pseudoscalar and vector mesons [8], two J P = 1/2 − Ω c states and one J P = 3/2 − Ω * c were observed, the first two in good agreement with the outcome of [7].…”

Investigating the excited Ωc0 states through ΞcK<

“…Besides, both Refs. [21,22] interpreted some Ω 0 c excited baryons as meson-baryon molecular states. To study the structure of the observed Ω [23].…”