D. R. Entem

Peripheral nucleon-nucleon scattering at fifth order of chiral perturbation theory

We present the two- and three-pion exchange contributions to the nucleon-nucleon interaction which occur at next-to-next-to-next-to-next-to-leading order (N4LO, fifth order) of chiral effective field theory, and calculate nucleon-nucleon scattering in peripheral partial waves with L>=3 using low-energy constants that were extracted from pi-N analysis at fourth order. While the net three-pion exchange contribution is moderate, the two-pion exchanges turn out to be sizeable and prevailingly repulsive, thus, compensating the excessive attraction characteristic for NNLO and N3LO. As a result, the N4LO predictions for the phase shifts of peripheral partial waves are in very good agreement with the data (with the only exception of the 1F3 wave). We also discuss the issue of the order-by-order convergence of the chiral expansion for the NN interaction.

Coupled channel approach to the structure of the X(3872)

We have performed a coupled channel calculation of the 1{sup ++} cc sector including qq and DD* molecular configurations. The calculation was done within a constituent quark model which successfully describes the meson spectrum, in particular, the cc 1{sup --} sector. Two and four-quark configurations are coupled using the {sup 3}P{sub 0} model. The elusive X(3872) meson appears as a new state with a high probability for the DD* molecular component. When the mass difference between neutral and charged states is included, a large D{sup 0}D*{sup 0} component is found which dominates for large distances and breaks isospin symmetry in the physical state. The original cc(2{sup 3}P{sub 1}) state acquires a sizable DD* component and can be identified with the X(3940). We study the B{yields}K{pi}{sup +{pi}-}J/{psi} and B{yields}KD{sup 0}D*{sup 0} decays, finding a good agreement with Belle and BABAR experimental data.

Renormalization of chiral two-pion exchange NN interactions: Momentum space versus coordinate space

The renormalization of the chiral np interaction in the {sup 1}S{sub 0} channel to next-to-next-to-next-to-leading order (N3LO) in Weinberg counting for the long-distance potential with one single momentum- and energy-independent counterterm is carried out. This renormalization scheme yields finite and unique results and is free of short-distance off-shell ambiguities. We observe good convergence in the entire elastic range below pion production threshold and find that there are some small physical effects missing in the purely pionic chiral NN potential with or without inclusion of explicit {delta} degrees of freedom. We also study the renormalizability of the standard Weinberg counting at next-to-leading order (NLO) and next-to-next-to-leading order (N2LO) when a momentum-dependent polynomial counterterm is included. Our numerical results suggest that the inclusion of this counterterm does not yield a convergent amplitude (at NLO and N2LO)

Scaling of the P03 strength in heavy meson strong decays

Abstract The phenomenological P 0 3 decay model has been extensively applied to calculate meson strong decays. The strength γ of the decay interaction is regarded as a free flavor independent constant and is fitted to the data. We calculate through the P 0 3 model the total strong decay widths of the mesons which belong to charmed, charmed-strange, hidden charm and hidden bottom sectors. The wave function of the mesons involved in the strong decays are given by a constituent quark model that describes well the meson phenomenology from the light to the heavy quark sector. A global fit of the experimental data shows that, contrarily to the usual wisdom, the γ depends on the reduced mass of the quark–antiquark pair in the decaying meson. With this scale-dependent strength γ, we are able to predict the decay width of orbitally excited B mesons not included in the fit.

Dominant contributions to the nucleon-nucleon interaction at sixth order of chiral perturbation theory

We present the dominant two- and three-pion-exchange contributions to the nucleon-nucleon interaction at sixth order (next-to-next-to-next-to-next-to-next-to-leading order, N5LO) of chiral perturbation theory. Phase shifts with orbital angular momentum L>=4 are given parameter free at this order and allow for a systematic investigation of the convergence of the chiral expansion. The N5LO contribution is prevailingly repulsive and considerably smaller than the N4LO one, thus, establishing the desired trend towards convergence. Using low-energy constants that were extracted from an analysis of pi-N scattering at fourth order, the predictions at N5LO are in excellent agreement with the empirical phase shifts of peripheral partial waves.

Molecular structures in the charmonium spectrum: the XYZ puzzle

We study in the framework of a constituent quark model the possible contributions of molecular structures to the XYZ charmonium-like states. We analyze simultaneously the structures and the possible molecular components in the coupled channel formalism. In the 1++ sector two states appear which could be identified with X(3872) and X(3940). The recently confirmed X(3915) state appears as a mixture of and components as a JPC = 0++ state in agreement with the new measurements. A second broad resonance which may correspond with the so-called Y(3940) state is found with these quantum numbers. In the JPC = 1−− sector we also found significant contributions of the molecular structures which may affect the phenomenology. In particular the study allows us to understand the G(3900) state recently observed in Belle and BaBar. All these resonances together with the prediction of the model of a structure for Z(3930) provide a reasonable scenario for the so-called XYZ states with masses near 3.9 GeV.

CONSTITUENT QUARK MODEL DESCRIPTION OF CHARMONIUM PHENOMENOLOGY

We review how quark models are able to describe the phenomenology of the charm meson sector. The spectroscopy and decays of charmonium and open charm mesons are described in a particular quark model and compared with the data and the results of other existing models in the literature. A quite reasonable global description of the heavy meson spectra is reached. A new assignment of the ψ(4415) resonance as a 3D state leaving aside the 4S state to the X(4360) is tested through the analysis of the resonance structure in e+e- exclusive reactions around the ψ(4415) energy region. We make tentative assignments of some of the XYZ mesons. To elucidate the structure of the 1+cs states, i.e., Ds1(2460) and Ds1(2536), we study the strong decay properties of the Ds1(2536) meson. We also perform a calculation of the branching fractions for the semileptonic decays of B and Bs mesons into final states containing orbitally excited charmed and charmed-strange mesons, which have become a very important source of information about the structure of heavy mesons. Analysis of the nonleptonic B-meson decays into D(*)DsJ are also included.

Towards a consistent approach to nuclear structure: EFT of two and many-body forces

We review the nuclear forces currently in use, i.e., the high-precision NN potentials of the 1990s and the nuclear two- and many-body forces based upon chiral effective field theory (EFT). We argue that the EFT approach is superior to any of the older schemes. Since accurate chiral forces are available now, the stage is set for microscopic nuclear structure to move into a new and exciting era.

Bottomonium spectrum revisited

We revisit the bottomonium spectrum motivated by the recently exciting experimental progress in the observation of new bottomonium states, both conventional and unconventional. Our framework is a nonrelativistic constituent quark model which has been applied to a wide range of hadronic observables from the light to the heavy quark sector and thus the model parameters are completely constrained. Beyond the spectrum, we provide a large number of electromagnetic, strong and hadronic decays in order to discuss the quark content of the bottomonium states and give more insights about the better way to determine their properties experimentally.

Nonperturbative renormalization of the chiral nucleon-nucleon interaction up to next-to-next-to-leading order

We study the nonperturbative renormalization of the nucleon-nucleon (NN) interaction at next-to-leading order (NLO) and next-to-next-to-leading order (NNLO) of chiral effective field theory. A systematic variation of the cutoff parameter is performed for values below the chiral symmetry breaking scale of about 1 GeV. The accuracy of the predictions is determined by calculating the