Mesonic and binding contributions to the nuclear Drell-Yan process

We have evaluated the Drell-Yan cross section in nuclei paying special attention to the meson cloud contribution from pion and rho-meson, for which an accurate calculation using the meson nuclear spectral functions is used. Similarly, the nucleonic contribution is evaluated in terms of a relativistic nucleon spectral function. Fair agreement with experiment is found for different nuclei and the results show a sizeable contribution from the renormalized meson cloud. In order to reproduce the experiment a novel element is introduced, consisting of a gradual energy loss of the incoming proton in its pass through the nucleus which produces a strong A dependence at x_1 large

Renormalization of the f(0)(980) and a(0)(980) scalar resonances in a nuclear medium

The meson-meson interaction in the scalar sector in the presence of a nuclear medium is studied with particular attention to the change of the properties of the f(0)(980) and a(0)(980) resonances. By using a chiral unitary approach which generates the f(0) and a(0) resonances and reproduces their free properties, we find that the position of the resonances in the medium is barely changed but their widths are considerably broadened. New many body corrections generating from higher orders in the chiral Lagrangian plus the contribution from N*h excitations, not considered before in connection with the pi pi interaction in the nuclear medium, are also investigated

The low lying scalar resonances in the D0 decays into K0s and f0(500), f0(980), a0(980)

The D0 decay into Ks0 and a scalar resonance, f0(500), f0(980), a0(980), are studied obtaining the scalar resonances from final state interaction of a pair of mesons produced in a first step in the D0 decay into Ks0 and the pair of pseudoscalar mesons. This weak decay is very appropriate for this kind of study because it allows to produce the three resonances in the same decay in a process that is Cabibbo-allowed, hence the rates obtained are large compared to those of B-0 decays into J/ψ and a scalar meson that have at least one Cabibbo-suppressed vertex. Concretely the a0(980) production is Cabibbo-allowed here, while it cannot be seen in the B-s0 decay into J/ψa0(980) and is doubly Cabibbo-suppressed in the B-0 decay into J/ψa0(980) and has not been identified there. The fact that the three resonances can be seen in the same reaction, because there is no isospin conservation in the weak decays, offers a unique opportunity to test the ideas of the chiral unitary approach where these resonances are produced from the interaction of pairs of pseudoscalar mesons

s-wave pion nucleon scattering lengths from pi N, pionic hydrogen, and deuteron data

The isoscalar and isovector scattering lengths (b(0),b(1)) are determined using a unitarized coupled channel approach based on chiral Lagrangians. Using experimental values of pionic hydrogen and deuterium as well as low energy piN scattering data, the free parameters of the model are calculated. Isospin violation is incorporated to a certain extent by working with physical particle masses. For the deuterium scattering length a(pi)(-)d new significant corrections concerning real and imaginary parts are evaluated, putting new constraints from pi(-)d scattering on the values of (b(0),b(1)). In particular, dispersion corrections, the influence of the Delta(1232) resonance, crossed terms and multiple scattering in a Faddeev approach are considered

Baryonic resonances from baryon decuplet-meson octet interaction

We study S-wave interactions of the baryon decuplet with the octet of pseudoscalar mesons using the lowest order chiral Lagrangian. In the S=1 sector, we find an attractive interaction in the ΔK channel with I=1 while it is repulsive for I=2. The attractive interaction leads to a pole in the second Riemann sheet of the complex plane and is manifested as a large strength in the scattering amplitude close to the ΔK threshold, which is not the case for I=2. We use the unitarized coupled channel approach to also investigate all the other possible values of strangeness and isospin. We find two bound states in the SU(3) limit corresponding to the octet and decuplet representations. These are found to split into eight different trajectories in the complex plane when the SU(3) symmetry is broken gradually. Finally, we are able to provide a reasonable description for a good number of 4-star 3/2− resonances listed by the Particle Data Group. In particular, the Ξ(1820), the Λ(1520) and the Σ(1670) states are well reproduced. We predict a few other resonances and also evaluate the couplings of the observed resonances to the various channels from the residues at the poles of the scattering matrix from where partial decay widths into different channels can be evaluated

Short range correlations in the pion s-wave self-energy of pionic atoms

We evaluate the contribution of second order terms to the pion-nucleus s-wave optical potential of pionic atoms generated by short range nuclear correlation. The corrections are sizeable because they involve the isoscalar s-wave πN amplitude for half off-shell situations where the amplitude is considerably larger than the on-shell one. In addition, the s-wave optical potential is reanalyzed by looking at all the different conventional contributions together lowest order, Pauli corrected rescattering term, second order absorptive effects, terms from the interaction of pions with the virtual pion cloud (chiral corrections) and correlation effects. Different off-shell extrapolations for the πN amplitude are used and it is found that, although some individual terms are sensitive to the extrapolation, the sum of them is rather insensitive. The results are compared with empirical values from best fits to the data and are found to be compatible, within theoretical and empirical uncertainties. The results do not rule out further contributions but they put stringent constraints on their strength

Meson resonances in the open and hidden charm sectors

We briefly expose our model for generating open and hidden charm resonances and present the most interesting results

Limits to the fixed center approximation to Faddeev equations: The case of the phi(2170)

The Fixed Center Approximation to the Faddeev equations (FCA) has been used lately with success in the study of bound systems of three hadrons. It is also important to set the limits of the approach in those problems to prevent proliferation of inaccurate predictions. In this paper we study the case of the ϕ(2170), which has been described by means of Faddeev equations as a resonant state of ϕ and KK¯, and show the problems derived from the use of the FCA in its study. At the same time we also expose the limitations of an alternative approach recently proposed

Recent developments on hadron interaction and dynamically generated resonances

In this talk I report on the recent developments in the subject of dynamically generated resonances. In particular I discuss the gamma p -> K-0 Sigma+ and gamma n -> K-0 Sigma(0) reactions, with a peculiar behavior around the K*(0)Lambda threshold, due to a 1/2(-) resonance around 2035 MeV. Similarly, I discuss a BES experiment, J/psi -> eta K*(0) (K) over bar*(0) decay, which provides evidence for a new h(1) resonance around 1830 MeV that was predicted from the vector-vector interaction. A short discussion is then made about recent advances in the charm and beauty sectors

Isoscalar S-wave π–π interaction in the nuclear medium

The s-wave isoscalar π π scattering amplitude in a nuclear medium has been evaluated using a non-perturbative unitary coupled channels method and the standard chiral Lagrangians. The method is successful describing the π π properties in vacuum, in the scalar-isoscalar channel up to 1.2 GeV giving rise to poles in the T matrix for the ƒ0(980) and the σ. The extension of the method to the nuclear medium implies the renormalization of the pions in the medium and also the introduction of interaction terms related to contact terms in the πN → ππN reaction.Vicente Vacas, Manuel Jose, [email protected] ; Oset Baguena , Eulogio, [email protected]