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.

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.

Abstract: We present a detailed study of the lowest-lying 1/2(-) and 3/2(-) Lambda Q resonances both in the heavy 2 2 quark (bottom and charm) and the strange sectors. We have paid special attention to the interplay between the constituent quark-model and chiral baryon-meson degrees of freedom, which are coupled using a unitarized scheme consistent with leading-order heavy quark symmetries. We show that the Lambda(b)(5912) [J(P) = 1/2(-)], Lambda(b)(5920) [J(P) = 3/2(-)] and the Lambda(c)(2625) [J(P) = 3/2-], and the Lambda(1520) [J(P) = 3/2(-)] admitting larger breaking corrections, are heavyquark spin-flavor siblings. They can be seen as dressed quark-model states with Sigma Q(()*()) pi molecular components of the order of 30%. The J(P)=1(-) Lambda(2595) has, however, a higher molecular 2 probability of at least 50%, and even values greater than 70% can be easily accommodated. This is because it is located almost on top of the threshold of the Sigma(c)pi pair, which largely influences its properties. Although the light degrees of freedom in this resonance would be coupled to spin-parity 1(-) as in the Lambda(b)(5912), Lambda(b)(5920) and Lambda(c)(2625), the Lambda(c)(2595) should not be considered as a heavy-quark spin-flavor partner of the former ones. We also show that the Lambda(1405) chiral two-pole pattern does not have analogs in the 1 – charmed and bottomed sectors, because the 2 N D-(*()) and N (B) over bar (()*()) channels do not play for heavy quarks the decisive role that the N (K) over bar does in the strange sector, and the notable influence of the bare quark-model states for the charm and bottom resonances. Finally, we predict the existence of two Lambda(b)(6070) and two Lambda(c)(2765) heavy-quark spin and flavor sibling odd parity states.