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Alarcon, J. M., Hiller Blin, A. N., Vicente Vacas, M. J., & Weiss, C. (2017). Peripheral transverse densities of the baryon octet from chiral effective field theory and dispersion analysis. Nucl. Phys. A, 964, 18–54.
Abstract: The baryon electromagnetic form factors are expressed in terms of two-dimensional densities describing the distribution of charge and magnetization in transverse space at fixed light-front time. We calculate the transverse densities of the spin-1/2 flavor-octet baryons at peripheral distances b = O(M-pi(-1)) using methods of relativistic chiral effective field theory (chi EFT) and dispersion analysis. The densities are represented as dispersive integrals over the imaginary parts of the form factors in the timelike region (spectral functions). The isovector spectral functions on the two-pion cut t > 4 M-pi(2) are calculated using relativistic chi EFT including octet and decuplet baryons. The chi EFT calculations are extended into the rho meson mass region using an N / D method that incorporates the pion electromagnetic form factor data. The isoscalar spectral functions are modeled by vector meson poles. We compute the peripheral charge and magnetization densities in the octet baryon states, estimate the uncertainties, and determine the quark flavor decomposition. The approach can be extended to baryon form factors of other operators and the moments of generalized parton distributions.
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Albaladejo, M., Bibrzycki, L., Dawid, S. M., Fernandez-Ramirez, C., Gonzalez-Solis, S., Hiller Blin, A. N., et al. (2022). Novel approaches in hadron spectroscopy. Prog. Part. Nucl. Phys., 127, 103981–75pp.
Abstract: The last two decades have witnessed the discovery of a myriad of new and unexpected hadrons. The future holds more surprises for us, thanks to new-generation experiments. Understanding the signals and determining the properties of the states requires a parallel theoretical effort. To make full use of available and forthcoming data, a careful amplitude modeling is required, together with a sound treatment of the statistical uncertainties, and a systematic survey of the model dependencies. We review the contributions made by the Joint Physics Analysis Center to the field of hadron spectroscopy.
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Cabrera, D., Hiller Blin, A. N., & Vicente Vacas, M. J. (2017). phi meson self-energy in nuclear matter from phi N resonant interactions. Phys. Rev. C, 95(1), 015201–9pp.
Abstract: The phi-meson properties in cold nuclear matter are investigated by implementing resonant phi N interactions as described in effective approaches including the unitarization of scattering amplitudes. Several N*-like states are dynamically generated in these models around 2 GeV, in the vicinity of the phi N threshold. We find that both these states and the non-resonant part of the amplitude contribute sizably to the phi collisional self-energy at finite nuclear density. These contributions are of a similar strength as the widely studied medium effects from the KK cloud. Depending on model details (position of the resonances and strength of the coupling to phi N) we report a phi broadening up to about 40-50 MeV, to be added to the phi -> KK in-medium decay width, and an attractive optical potential at threshold up to about 35 MeV at normal matter density. The phi spectral function develops a double peak structure as a consequence of the mixing of resonance-hole modes with the phi quasiparticle peak. The former results point in the direction of making up for missing absorption as reported in phi nuclear production experiments.
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Cabrera, D., Hiller Blin, A. N., Vicente Vacas, M. J., & Fernandez de Cordoba, P. (2017). phi meson transparency in nuclei from phi N resonant interactions. Phys. Rev. C, 96(3), 034618–6pp.
Abstract: We investigate the phi meson nuclear transparency using some recent theoretical developments on the phi in medium self-energy. The inclusion of direct resonant phi N scattering and the kaon decay mechanisms leads to a phi width much larger than in most previous theoretical approaches. The model has been confronted with photoproduction data from CLAS and LEPS and the recent proton induced phi production from COSY finding an overall good agreement. The results support the need of a quite large direct phi N-scattering contribution to the self-energy.
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Guerrero Navarro, G. H., Vicente Vacas, M. J., Hiller Blin, A. N., & Yao, D. L. (2019). Pion photoproduction off nucleons in covariant chiral perturbation theory. Phys. Rev. D, 100(9), 094021–18pp.
Abstract: Pion photoproduction off the nucleon close to threshold is studied in covariant baryon chiral perturbation theory at O(p(3)) in the extended-on-mass-shell scheme, with the explicit inclusion of the Delta(1232) resonance using the delta counting. The theory is compared to the available data of cross sections and polarization observables for all the charge channels. Most of the necessary low-energy constants arc well known from the analysis of other processes and the comparison with data constrains some of the still unknown ones. The Delta(1232) contribution is significant in improving the agreement with data, even at the low energies considered.
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Gutsche, T., Hiller Blin, A. N., Kovalenko, S., Kuleshov, S., Lyubovitskij, V. E., & Vicente Vacas, M. J. (2017). CP-violating decays of the pseudoscalars eta and eta' and their connection to the electric dipole moment of the neutron. Phys. Rev. D, 95(3), 036022–9pp.
Abstract: Using the present upper bound on the neutron electric dipole moment, we give an estimate for the upper limit of the CP-violating couplings of the eta(eta') to the nucleon. Using this result, we then derive constraints on the CP-violating eta(eta')pi pi couplings, which define the two-pion CP-violating decays of the eta and eta' mesons. Our results are relevant for the running and planned measurements of rare decays of the. eta and eta' mesons by the GlueX Collaboration at JLab and the LHCb Collaboration at CERN.
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Hiller Blin, A. N. (2017). Systematic study of octet-baryon electromagnetic form factors in covariant chiral perturbation theory. Phys. Rev. D, 96(9), 093008–19pp.
Abstract: We perform a complete and systematic calculation of the octet-baryon form factors within the fully covariant approach of SU(3) chiral perturbation theory at O(p(3)). We use the extended on-mass shell renormalization scheme and include explicitly the vector mesons and the spin-3/2 decuplet intermediate states. Comparing these predictions with data including magnetic moments, charges, and magnetic radii, we determine the unknown low-energy constants and give predictions for yet unmeasured observables, such as the magnetic moment of the Sigma(0) and the charge and magnetic radii of the hyperons.
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Hiller Blin, A. N., Fernandez-Ramirez, C., Jackura, A., Mathieu, V., Mokeev, V. I., Pilloni, A., et al. (2016). Studying the P-c(4450) resonance in J/psi photoproduction off protons. Phys. Rev. D, 94(3), 034002–8pp.
Abstract: A resonancelike structure, the P-c(4450), has recently been observed in the J/psi p spectrum by the LHCb Collaboration. We discuss the feasibility of detecting this structure in J/psi photoproduction in the CLAS12 experiment at JLab. We present a first estimate of the upper limit for the branching ratio of the P-c (4450) to J/psi p. Our estimates, which take into account the experimental resolution effects, predict that it will be possible to observe a sizable cross section close to the J/psi production threshold and shed light on the P-c(4450) resonance in the future photoproduction measurements.
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Hiller Blin, A. N., Gutsche, T., Ledwig, T., & Lyubovitskij, V. E. (2015). Hyperon forward spin polarizability gamma(0) in baryon chiral perturbation theory. Phys. Rev. D, 92(9), 096004–9pp.
Abstract: We present the calculation of the hyperon forward spin polarizability gamma(0) using manifestly Lorentz-covariant baryon chiral perturbation theory including the intermediate contribution of the spin-3/2 states. As at the considered order the extraction of. 0 is a pure prediction of chiral perturbation theory, the obtained values are a good test for this theory. After including explicitly the decuplet states, our SU(2) results have a very good agreement with the experimental data and we extend our framework to SU(3) to give predictions for the hyperons'. 0 values. Prominent are the Sigma(-) and Xi(-) baryons as their photon transition to the decuplet is forbidden in SU(3) symmetry and therefore they are not sensitive to the explicit inclusion of the decuplet in the theory.
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Hiller Blin, A. N., Ledwig, T., & Vicente Vacas, M. J. (2016). Delta(1232) resonance in the (gamma)over-right-arrowp -> p pi(0) reaction at threshold. Phys. Rev. D, 93(9), 094018–19pp.
Abstract: We calculate the neutral pion photoproduction on the proton near threshold in covariant baryon chiral perturbation theory, including the Delta(1232) resonance as an explicit degree of freedom, up to chiral order p(7/2) in the delta counting. We compare our results with recent low-energy data from the Mainz Microtron for angular distributions and photon asymmetries. The convergence of the chiral series of the covariant approach is found to improve substantially with the inclusion of the Delta(1232) resonance.
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