Baryon states with open charm in the extended local hidden gauge approach

Abstract

In this paper we examine the interaction of DN and D * N states, together with their coupled channels, by using an extension of the local hidden gauge formalism from the light meson sector, which is based on heavy quark spin symmetry. The scheme is based on the use of the impulse approximation at the quark level, with the heavy quarks acting as spectators, which occurs for the dominant terms where there is the exchange of a light meson. The pion exchange and the WeinbergTomozawa interactions are generalized and with this dynamics we look for states generated from the interaction, with a unitary coupled channels approach that mixes the pseudoscalar-baryon and vector-baryon states. We find two states with nearly zero width which are associated to the Λ c (2595) and Λ c (2625). The lower state, with J P = 1/2 − , couples to DN and D * N , and the second one, with J P = 3/2 − , to D * N . In addition to these two Λ c states, we find four more states with I = 0, one of them nearly degenerate in two states of J = 1/2, 3/2. Furthermore we find three states in I = 1, two of them degenerate in J = 1/2, 3/2. * liangwh@gxnu.edu.cn 1 I. INTRODUCTIONIn dealing with hadronic states involving heavy quarks (charm or beauty) the heavy quark spin symmetry [1][2][3][4] plays an important role and serves as a guiding principle to proceed with calculations. Heavy quark spin symmetry (HQSS) has been applied to calculate baryon spectra in Refs. [5][6][7][8][9][10][11][12]. The basic idea behind these works is to use HQSS to reduce the freedom in the interaction, which is then written in terms of a few parameters which are adjusted to some experimental data. Then predictions on spectra of baryons with charm or beauty, or hidden charm and beauty are made. In Ref.[5] an SU(8) spin-flavor scheme is used, to account for the spin symmetry, in order to obtain the interaction, and a coupled channels unitary approach is implemented to obtain poles in the scattering matrices, which correspond to the baryon resonance states. In particular the Λ c (2595) state is obtained and shown to couple largely to the D * N channel. In Ref.[8] the SU(8) scheme is once again used, but with some symmetry breaking, to match with an extension of the WeinbergTomozawa interaction in SU(3). Among other resonances, the states Λ c (2595) (J P = 1/2 − ) and Λ c (2625) (J P = 3/2 − ) are obtained. Further steps on the relationship of the Weinberg-Tomozawa interaction and HQSS are given in Refs. [10,13], where it is shown that this interaction, which stems from the exchange of vector mesons in the local hidden gauge approach [14][15][16] (see also Ref.[17] for practical rules), fulfills the HQSS. Indeed, the dominant terms correspond to the exchange of light vectors (the exchange of heavy vectors is suppressed), the heavy quarks act as spectators and hence the interaction does not depend on them. HQSS is then automatically fulfilled. Another step forward in this direction was given in Ref. [18], where using the impulse approximation at the quark level, the Weinb...

The hidden-charm pentaquark and tetraquark states

“…In this review we introduce this method and review their results briefly. However, we shall not discuss its application for open-charm baryons [274,275,276,277,278].…”

Hidden-charm pentaquarks as a meson-baryon molecule with coupled channels for D¯(*)ΛYamaguchi1, Santopinto2 2017Phys. Rev. D642410View full textAdd to dashboardCite

“…This mechanism has been suggested to have an important role in theD ( * ) N system in Refs. [43][44][45][46][47][48][49][50]. The coupledchannel analysis with the mixing of S -wave and Dwave was not performed in Refs.…”

Resonance on top of thresholds: TheΛc(2595)+as an extremely fine-tuned state

“…This point has prompted several studies of this state by analyzing πΣ c scattering, as well as including other relevant heavier intermediate states, such as ND, ND * , etc [14][15][16][17][18][19][20][21][22][23]. In these latter works, the unitarized chiral perturbation theory (UChPT) approach 1 is extended from the strange baryons to the charm sector, mainly motivated by the similarity of the isoscalar S-wave Λ(1405) and Λ c (2595) baryons [14][15][16][17][18][19][20][21][22][23]. The former state has a mass between the thresholds of πΣ andKN and it also couples strongly to both channels [24,27,31,32].…”