Assignments of ΛQ\Lambda_Q and ΞQ\Xi_Q baryons in the heavy quark-light diquark picture

We apply a new mass formula which is derived analytically in the relativistic flux tube model to the mass spectra of $\Lambda_Q$ and $\Xi_Q$ (\emph{Q} = \emph{c} or \emph{b} quark) baryons. To this end, the heavy quark-light diquark picture is employed. We find that all masses of the available $\Lambda_Q$ and $\Xi_Q$ states can be understood well. The assignments to these states do not appear to contradict the strong decay properties. $\Lambda_c(2760)^+$ and $\Xi_c(2980)$ are assigned to the first radial excitations with $J^P = 1/2^+$. $\Lambda_c(2940)^+$ and $\Xi_c(3123)$ might be the 2\emph{P} states. The $\Lambda_c(2880)^+$ and $\Xi_c(3080)$ are the good 1\emph{D} candidates with $J^P = 5/2^+$. $\Xi_c(3055)$ is likely to be a 1\emph{D} state with $J^P = 3/2^+$. $\Lambda_b(5912)^0$ and $\Lambda_b(5920)^0$ favor the 1\emph{P} assignments with $J^P = 1/2^-$ and $3/2^-$, respectively. We propose a search for the $\tilde{\Lambda}_{c2}(5/2^-)$ state which can help to distinguish the diquark and three-body schemes.Comment: 9 tables, more discussions and references adde

Spiral wave chimeras in locally coupled oscillator systems

The recently discovered chimera state involves the coexistence of synchronized and desynchronized states for a group of identical oscillators. This fascinating chimera state has until now been found only in non-local or globally coupled oscillator systems. In this work, we for the first time show numerical evidence of the existence of spiral wave chimeras in reaction-diffusion systems where each element is locally coupled by diffusion. This spiral wave chimera rotates inwardly, i.e., coherent waves propagate toward the phase randomized core. A continuous transition from spiral waves with smooth core to spiral wave chimeras is found as we change the local dynamics of the system. Our findings on the spiral wave chimera in locally coupled oscillator systems largely improve our understanding of the chimera state and suggest that spiral chimera states may be found in natural systems which can be modeled by a set of oscillators indirectly coupled by a diffusive environment.Comment: 5 pages, 5 figure

Hyper-accreting black hole as GRB central engine. I: Baryon loading in GRB jets

A hyper-accreting stellar-mass black hole has been long speculated as the best candidate of central engine of gamma-ray bursts (GRBs). Recent rich observations of GRBs by space missions such as Swift and Fermi pose new constraints on GRB central engine models. In this paper, we study the baryon loading processes of a GRB jet launched from a black hole central engine. We consider a relativistic jet powered by $\nu \bar\nu$-annihilation or by the Blandford-Znajek (BZ) mechanism. We consider baryon loading from a neutrino-driven wind from a neutrino-cooling-dominated accretion flow. For a magnetically dominated BZ jet, we consider neutron-drifting from the magnetic wall surrounding the jet and subsequent positron capture and proton-neutron inelastic collisions. The minumim baryon loads in both types of jet are calculated. We find that in both cases, a more luminous jet tends to be more baryon poor. A neutrino-driven "fireball" is typically "dirtier" than a magnetically dominated jet, while a magnetically dominated jet can be much cleaner. Both models have the right scaling to interpret the empirical $\Gamma-L_{\rm iso}$ relation discovered recently. Since some neutrino-driven jets have too much baryon loading as compared with the data, we suggest that at least a good fraction of GRBs should have a magnetically dominated central engine.Comment: 9 pages, 2 figures; Accepted for publication in Ap