Abstract: The DO Collaboration has recently seen a resonant-like peak in the B-s pi invariant mass spectrum, claimed to be a new state called X(5568). Using a B-s pi-B (K) over bar coupled channel analysis, implementing unitarity, and with the interaction derived from Heavy Meson Chiral Perturbation Theory, we are able to reproduce the reported spectrum, with a pole that can be associated to the claimed X(5568) state, and with mass and width in agreement with the ones reported in the experimental analysis. However, if the T-matrix regularization is performed by means of a momentum cutoff, the value for the latter needed to reproduce the spectrum is Lambda = 2.80 +/- 0.04 GeV, which is much larger than a “natural” value Lambda similar or equal to 1 GeV. In view of this, it is difficult to interpret the nature of this new state. This state would not qualify as a resonance dynamically generated by the unitarity loops. Assuming the observed peak to correspond to a physical state, we make predictions for partners in the D, D*, and B* sectors. Their observation (or lack thereof) would shed light into this issue.

Abstract: We study the electromagnetic form factors of the doubly charmed baryons, using covariant chiral perturbation theory within the extended on-mass-shell scheme. Vector-meson contributions are also taken into account. We present results for the baryon magnetic moments, charge, and magnetic radii. While some of the chiral Lagrangian parameters could be set to values determined in previous works, the available lattice results for Xi(+)(CC) and Omega(+)(CC) only allow for robust constraints on the low-energy constant combination, c(89) (= -1/3 c(8) + 4c(9)). The couplings of the doubly charmed baryons to the vector mesons have been estimated assuming the Okubo-Zweig-Iizuka rule. We also give the expressions for the form factors of the double-beauty baryons considering the masses predicted in the framework of quark models. A comparison of our results with those obtained in heavy baryon chiral perturbation theory at the same chiral order is made.

Abstract: In this work, we study systems composed of a rho/omega and B* meson pair. We find three bound states in isospin, spin-parity channels (1/2, 0(+)), (1/2, 1(+)), and (1/2, 2(+)). The state with J = 2 can be a good candidate for the B-2*(5747). We also study the rho B system, and a bound state with mass 5728 MeV and width around 20 MeV is obtained, which can be identified with the B-1(5721) resonance. In the case of I = 3/2, one obtains repulsion and, thus, no exotic (molecular) mesons in this sector are generated in the approach.