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Gomez Dumm, D., Noguera, S., & Scoccola, N. N. (2023). Charged meson masses under strong magnetic fields: Gauge invariance and Schwinger phases. Phys. Rev. D, 108(1), 016012–29pp.
Abstract: We study the role of the Schwinger phase (SP) that appears in the propagator of a charged particle in the presence of a static and uniform magnetic field (B) over right arrow. We first note that this phase cannot be removed by a gauge transformation; far from this, we show that it plays an important role in the restoration of the symmetries of the system. Next, we analyze the effect of SPs in the one-loop corrections to charged pion and rho meson self-energies. To carry out this analysis we consider first a simple form for the meson-quark interactions, and then we study the pi(+) and rho(-) propagators within the Nambu-Jona-Lasinio model, performing a numerical analysis of the B dependence of meson lowest energy states. For both pi(+) and rho(-) mesons, we compare the numerical results arising from the full calculation-in which SPs are included in the propagators, and meson wave functions correspond to states of definite Landau quantum number-and those obtained within alternative schemes in which SPs are neglected (or somehow eliminated) and meson states are described by plane waves of definite four-momentum.
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Carlomagno, J. P., Gomez Dumm, D., Izzo Villafañe, M. F., Noguera, S., & Scoccola, N. N. (2022). Charged pseudoscalar and vector meson masses in strong magnetic fields in an extended NJL model. Phys. Rev. D, 106(9), 094035–17pp.
Abstract: The mass spectrum of pi(+) and rho(+) mesons in the presence of a static uniform magnetic field (B) over right arrow is studied within a two-flavor Nambu-Jona-Lasinio-like model. We improve previous calculations, taking into account the effect of Schwinger phases carried by quark propagators and using an expansion of meson fields in terms of the solutions of the corresponding equations of motion for nonzero B. It is shown that the meson polarization functions are diagonal in this basis. Our numerical results for the rho(+) meson spectrum are found to disfavor the existence of a meson condensate induced by the magnetic field. In the case of the pi(+) meson, pi-rho mixing effects are analyzed for the meson lowest-energy state. The predictions of the model are compared with available lattice QCD results.
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Gomez Dumm, D., Noguera, S., & Scoccola, N. N. (2017). eta-gamma and eta(')-gamma transition form factors in a nonlocal NJL model. Phys. Rev. D, 95(5), 054006–19pp.
Abstract: We study the eta and eta(') distribution amplitudes (DAs) in the context of a nonlocal SU(3)(L) circle times SUd(3)(R) chiral quark model. The corresponding Lagrangian allows us to reproduce the phenomenological values of pseudoscalar meson masses and decay constants, as well as the momentum dependence of the quark propagator arising from lattice calculations. It is found that the obtained DAs have two symmetric maxima, which arise from new contributions generated by the nonlocal character of the interactions. These DAs are then applied to the calculation of the eta-gamma and eta(')-gamma transition form factors. Implications of our results regarding higher twist corrections and/or contributions to the transition form factors originated by gluon-gluon components in the eta and eta(') mesons are discussed.
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Gomez Dumm, D., Noguera, S., & Scoccola, N. N. (2012). Form factors of radiative pion decays in nonlocal chiral quark models. Phys. Rev. D, 86(7), 074020–10pp.
Abstract: We study the radiative pion decay pi(+) -> e(+) nu(e)gamma within nonlocal chiral quark models that include wave function renormalization. In this framework we analyze the momentum dependence of the vector form factor F-V(q(2)) and the slope of the axial-vector form factor F-A(q(2)) at threshold. Our results are compared with available experimental information and with the predictions given by the Nambu-Jona-Lasinio model. In addition we calculate the low energy constants l(5) and l(6), comparing our results with the values obtained in chiral perturbation theory.
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Gomez Dumm, D., Roig, P., Pich, A., & Portoles, J. (2010). Hadron structure in tau -> KK pi nu(tau) decays. Phys. Rev. D, 81(3), 034031–17pp.
Abstract: We analyze the hadronization structure of both vector and axial-vector currents leading to tau -> KK pi nu(tau) decays. At leading order in the 1/N-C expansion, and considering only the contribution of the lightest resonances, we work out, within the framework of the resonance chiral Lagrangian, the structure of the local vertices involved in those processes. The couplings in the resonance theory are constrained by imposing the asymptotic behavior of vector and axial-vector spectral functions ruled by QCD. In this way we predict the hadron spectra and conclude that, contrary to previous assertions, the vector contribution dominates by far over the axial-vector one in all KK pi charge channels.
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