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1. Interactions of πK, ππK and KKπ systems at maximal isospin from lattice QCD

   https://doi.org/10.1007/JHEP05(2023)137  

   Draper, Zachary T.; Hanlon, Andrew D.; Hörz, Ben; Morningstar, Colin; Romero-López, Fernando; Sharpe, Stephen R. (May 2023, Journal of High Energy Physics)

   A<sc>bstract</sc> We study the interactions of systems of two and three nondegenerate mesons composed of pions and kaons at maximal isospin using lattice QCD, specificallyπ⁺K⁺,π⁺π⁺K⁺andK⁺K⁺π⁺. Utilizing the stochastic LapH method, we determine the spectrum of these systems on two CLSN_f= 2 + 1 ensembles with pion masses of 200 MeV and 340 MeV, and include many levels in different momentum frames. We constrain the K matrices describing two- and three-particle interactions by fitting the spectrum to the results predicted by the finite-volume formalism, including up topwaves. This requires also results for theπ⁺π⁺andK⁺K⁺spectrum, which have been obtained previously on the same configurations. We explore different fitting strategies, comparing fits to energy shifts with fits to energies boosted to the rest frame, and also comparing simultaneous global fits to all relevant two- and three-particle channels to those where we first fit two-particle channels and then add in the three-particle information. We provide the first determination of the three-particle K matrix inπ⁺π⁺K⁺andK⁺K⁺π⁺systems, finding statistically significant nonzero results in most cases. We includesandpwaves in the K matrix forπ⁺K⁺scattering, finding evidence for an attractivep-wave scattering length. We compare our results to Chiral Perturbation Theory, including an investigation of the impact of discretization errors, for which we provide the leading order predictions obtained using Wilson Chiral Perturbation Theory. 

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2. Two- and three-meson scattering amplitudes with physical quark masses from lattice QCD

   https://doi.org/10.1103/bx16-lp3r  

   Dawid, Sebastian M; Draper, Zachary T; Hanlon, Andrew D; Hörz, Ben; Morningstar, Colin; Romero-López, Fernando; Sharpe, Stephen R; Skinner, Sarah (July 2025, Physical Review D)

   We study systems of two and three mesons composed of pions and kaons at maximal isospin using four CLS ensembles with $a\approx 0.063\mathrm{fm}$, including one with approximately physical quark masses. Using the stochastic Laplacian-Heaviside method, we determine the energy spectrum of these systems including many levels in different momentum frames and irreducible representations. Using the relativistic two- and three-body finite-volume formalism, we constrain the two- and three-meson K matrices, including not only the leading $s$wave, but also $p$and $d$waves. By solving the three-body integral equations, we determine, for the first time, the physical-point scattering amplitudes for $3{\pi }^{+}$, $3K^{+}$, ${\pi }^{+}{\pi }^{+}{K}^{+}$, and $K^{+}{K}^{+}{\pi }^{+}$systems. These are determined for total angular momentum $J^P=0^{-}$, $1^{+}$, and $2^{-}$. We also obtain accurate results for $2{\pi }^{+}$, ${\pi }^{+}{K}^{+}$, and $2K^{+}$phase shifts. We compare our results to chiral perturbation theory and to phenomenological fits. 

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3. Three-body resonances in the φ4 theory

   https://doi.org/10.1007/JHEP02(2023)252  

   Garofalo, Marco; Mai, Maxim; Romero-López, Fernando; Rusetsky, Akaki; Urbach, Carsten (February 2023, Journal of High Energy Physics)

   A bstract We study the properties of three-body resonances using a lattice complex scalar φ 4 theory with two scalars, with parameters chosen such that one heavy particle can decay into three light ones. We determine the two- and three-body spectra for several lattice volumes using variational techniques, and then analyze them with two versions of the three-particle finite-volume formalism: the Relativistic Field Theory approach and the Finite-Volume Unitarity approach. We find that both methods provide an equivalent description of the energy levels, and we are able to fit the spectra using simple parametrizations of the scattering quantities. By solving the integral equations of the corresponding three-particle formalisms, we determine the pole position of the resonance in the complex energy plane and thereby its mass and width. We find very good agreement between the two methods at different values of the coupling of the theory. 

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4. QCD Predictions for Physical Multimeson Scattering Amplitudes

   https://doi.org/10.1103/6nql-yrhw  

   Dawid, Sebastian M; Draper, Zachary T; Hanlon, Andrew D; Hörz, Ben; Morningstar, Colin; Romero-López, Fernando; Sharpe, Stephen R; Skinner, Sarah (July 2025, Physical Review Letters)

   We use lattice QCD calculations of the finite-volume spectra of systems of two and three mesons to determine, for the first time, three-particle scattering amplitudes with physical quark masses. Our results are for combinations of π+ and K+, at a lattice spacing a=0.063 fm, and in the isospin-symmetric limit. We also obtain accurate results for maximal-isospin two-meson amplitudes, with those for ${\pi }^{+}{K}^{+}$and $2K^{+}$being the first determinations at the physical point. Dense lattice spectra are obtained using the stochastic Laplacian-Heaviside method, and the analysis leading to scattering amplitudes is done using the relativistic finite-volume formalism. Results are compared to chiral perturbation theory and to phenomenological fits to experimental data, finding good agreement. 

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5. The Effect of Particle Composition and Concentration on the Partitioning Coefficient for Mercury in Three Ocean Basins

   https://doi.org/10.3389/fenvc.2021.660267  

   Cui, Xinyun; Lamborg, Carl H.; Hammerschmidt, Chad R.; Xiang, Yang; Lam, Phoebe J. (May 2021, Frontiers in Environmental Chemistry)

   The downward flux of sinking particles is a prominent Hg removal and redistribution process in the ocean; however, it is not well-constrained. Using data from three U.S. GEOTRACES cruises including the Pacific, Atlantic, and Arctic Oceans, we examined the mercury partitioning coefficient, K d , in the water column. The data suggest that the K d varies widely over three ocean basins. We also investigated the effect of particle concentration and composition on K d by comparing the concentration of small-sized (1–51 μm) suspended particulate mass (SPM) as well as its compositional fractions in six different phases to the partitioning coefficient. We observed an inverse relationship between K d and suspended particulate mass, as has been observed for other metals and known as the “particle concentration effect,” that explains much of the variation in K d . Particulate organic matter (POM) and calcium carbonate (CaCO 3 ) dominated the Hg partitioning in all three ocean basins while Fe and Mn could make a difference in some places where their concentrations are elevated, such as in hydrothermal plumes. Finally, our estimated Hg residence time has a strong negative correlation with average log bulk K d , indicating that K d has significant effect on Hg residence time. 

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