We make a theoretical study of the s-wave interaction of the nonet of vector mesons with the octet of pseudoscalar mesons starting from a chiral invariant Lagrangian and implementing unitarity in coupled channels. By looking for poles in the unphysical Riemann sheets of the unitarized scattering amplitudes, we get two octets and one singlet of axial-vector dynamically generated resonances. The poles found can be associated to most of the low lying axial-vector resonances quoted in the Particle Data Book: b 1 (1235), h 1 (1170), h 1 (1380), a 1 (1260), f 1 (1285) and two poles to the K 1 (1270) resonance. We evaluate the couplings of the resonances to the V P states and the partial decay widths in order to reinforce the arguments in the discussion.

We perform a theoretical analysis of the Λ b → J/ψK − p reaction from where a recent LHCb experiment extracts a Λ(1405) contribution in the K − p spectrum close to threshold and two baryon states of hidden charm in the J/ψ p spectrum. We recall that baryon states of this type have been theoretically predicted matching the mass, width and J P of the experiment, concretely some states built up from the J/ψ N ,D * Λc,D * Σc,DΣ * c andD * Σ * c coupled channels. We assume that the observed narrow state around 4450 MeV has this nature and we are able to describe simultaneously the shapes and relative strength of the the K − p mass distribution close to threshold and the peak of the J/ψ p distribution, with values of the J/ψ p coupling to the resonance in line with the theoretical ones. The non trivial matching of many properties gives support to a J P = 3/2 − assignment to this state and to its nature as a molecular state mostly made ofD * Σc andD * Σ * c .PACS numbers:

The axial vector meson K1(1270) was studied within the chiral unitary approach, where it was shown that it has a two-pole structure. We reanalyze the high-statistics WA3 experiment K − p → K − π + π − p at 63 GeV, which established the existence of both K1(1270) and K1(1400), and we show that it clearly favors our two-pole interpretation. We also reanalyze the traditional K-matrix interpretation of the WA3 data and find that the good fit of the data obtained there comes from large cancellations of terms of unclear physical interpretation.

The radiative decay of the axial-vector resonances into a pseudoscalar meson and a photon is studied using the vector meson Lagrangian obtained from the hidden gauge symmetry (HGS) formalism. The formalism is well suited to study this problem since it deals with pseudoscalar and vector mesons in a unified way, respecting chiral invariance. We show explicitly the gauge invariance of the set of diagrams that appear in the approach and evaluate the radiative decay width of the a1(1260) and b1(1235) axial vector meson resonances into pi gamma. We also include the contribution of loops involving anomalous couplings and compare the results to those obtained previously within another formalism.Comment: 24 pages, 6 tables, 11 figure

We make a theoretical study of the J/Ψ decays into ωππ, φππ, ωKK and φKK using the techniques of the chiral unitary approach stressing the important role of the scalar resonances dynamically generated through the final state interaction of the two pseudoscalar mesons. We also discuss the importance of new mechanisms with intermediate exchange of vector and axial-vector mesons and the role played by the OZI rule in the J/Ψφππ vertex, quantifying its effects. The results nicely reproduce the experimental data for the invariant mass distributions in all the channels considered.