Smith, W. A., Glazier, D. I., Mathieu, V., Albaladejo, M., Albrecht, M., Baldwin, Z., et al. (2023). Ambiguities in partial wave analysis of two spinless meson photoproduction. Phys. Rev. D, 108(7), 076001–12pp.
Abstract: We describe the formalism to analyze the mathematical ambiguities arising in partial-wave analysis of two spinless mesons produced with a linearly polarized photon beam. We show that partial waves are uniquely defined when all accessible observables are considered, for a wave set which includes S and D waves. The inclusion of higher partial waves does not affect our results, and we conclude that there are no mathematical ambiguities in partial-wave analysis of two mesons produced with a linearly polarized photon beam. We present Monte Carlo simulations to illustrate our results.
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Winney, D., Fernandez-Ramirez, C., Pilloni, A., Hiller Blin, A. N., Albaladejo, M., Bibrzycki, L., et al. (2023). Dynamics in near-threshold J/ψ photoproduction. Phys. Rev. D, 108, 054018–15pp.
Abstract: The study of J/ψ photoproduction at low energies has consequences for the understanding of multiple aspects of nonperturbative QCD, ranging from mechanical properties of the proton to the binding inside nuclei and the existence of hidden-charm pentaquarks. Factorization of the photon-c¯c and nucleon dynamics or vector meson dominance are often invoked to justify these studies. Alternatively, open-charm intermediate states have been proposed as the dominant mechanism underlying J/ψ photoproduction. As the latter violates this factorization, it is important to estimate the relevance of such contributions. We analyze the latest differential and integrated photoproduction cross sections from the GlueX and J/ψ−007 experiments. We show that the data can be adequately described by a small number of partial waves, which we parametrize with generic models enforcing low-energy unitarity. The results suggest a non-negligible contribution from open-charm intermediate states. Furthermore, most of the models present an elastic scattering length incompatible with previous extractions based on vector meson dominance and thus call into question its applicability to heavy mesons. Our results indicate a wide array of physics possibilities that are compatible with present data and need to be disentangled.
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