arXiv subjects

André Baião Raposo

Publications and source records attributed to André Baião Raposo.

5 recordsLinked to original sources

arXiv2026

Preliminary study of the $H$ dibaryon in $N_{\rm f}=2+1$ lattice QCD

We present preliminary results on the $I=0$, $S=-2$ $H$ dibaryon in $N_{\rm f}=2+1$ QCD. The calculation is performed with heavier-than-physical quarks ($m_π\approx 280$ MeV) on a single CLS ensemble. Correlation matrices are constructed using the distillation technique and the three relevant channels, $ΛΛ$, $NΞ$, $ΣΣ$, are investigated to determine the interacting spectrum relevant for $S$-wave across multiple momentum frames. The scattering amplitude is determined by solving the corresponding two-body quantization condition. These preliminary results are part of the ongoing efforts to determine the properties of di-hyperons and to establish whether the $H$ dibaryon exists down to physical quark masses.

hep-lat↗

arXiv2026

Three-body study of the $T_{cc}(3875)^+$ from lattice QCD

We discuss an ongoing first lattice study of the doubly-charmed tetraquark $T_{cc}^+$(3875) via a three-body approach. We investigate the $DDπ$ system in the $I=0$, $C=2$ sector, where the $T_{cc}^+$ appears as a pole in the $J^P = 1^+$ $DDπ$ elastic scattering amplitude. The approach automatically incorporates two-body $DD^*$ and three-body $DDπ$ effects and treats left-hand cuts due to single $π$ exchanges. Two CLS ensembles, X252 and X253, with pion mass $M_π\approx 280$ MeV, are used, and an operator set comprised of two- and three-hadron and tetraquark operators is employed to extract finite-volume energies. Additional inputs are required for the three-body finite-volume analysis, in the form of amplitudes for the $I=1$ $DD$ and $I=1/2$ $Dπ$ two-body subsystems. We present preliminary results for these subchannels and perform exploratory three-body spectra determinations for simple choices of the three-particle K-matrix $\mathcal{K}_{\text{df}, 3}$, allowing a first comparison to the lattice spectrum.

hep-lat↗

arXiv2025

Extracting scattering amplitudes for arbitrary two-particle systems with one-particle left-hand cuts via lattice QCD

We derive a general formalism that relates the spectrum of two-particle systems in a finite volume to physical scattering amplitudes, taking into account the presence of any left-hand branch cuts due to single-particle exchanges. The method first relates the finite-volume spectrum to an infinite-volume short-range quantity, denoted \mathcal{M}_0, and then relates the latter to the physical scattering amplitudes via known integral equations. The derivation of both relations is performed using all-orders perturbation theory and is exact up to neglected exponentially suppressed volume dependence. The relations hold for arbitrary two-particle systems with any number of coupled channels, non-identical and non-degenerate particles, and any intrinsic spin.

hep-lat↗

arXiv2024

Finite-volume scattering on the left-hand cut

The two-particle finite-volume scattering formalism derived by Lüscher and generalized in many subsequent works does not hold for energies far enough below the two-particle threshold to reach the nearest left-hand cut. The breakdown of the formalism is signaled by the fact that a real scattering amplitude is predicted in a regime where it should be complex. In this work, we address this limitation by deriving an extended formalism that includes the nearest branch cut, arising from single particle exchange. We focus on two-nucleon ($NN \to NN$) scattering, for which the cut arises from pion exchange, but give expressions for any system with a single channel of identical particles. The new result takes the form of a modified quantization condition that can be used to constrain an intermediate K-matrix in which the cut is removed. In a second step, integral equations, also derived in this work, must be used to convert the K-matrix to the physical scattering amplitude. We also show how the new formalism reduces to the standard approach when the $N \to N π$ coupling is set to zero.

hep-lat↗

arXiv2023

The Lüscher scattering formalism on the $t$-channel cut

The Lüscher scattering formalism, the standard approach for relating the discrete finite-volume energy spectrum to two-to-two scattering amplitudes, fails when analytically continued so far below the infinite-volume two-particle threshold that one encounters the $t$-channel cut. This is relevant, especially in baryon-baryon scattering applications, as finite-volume energies can be observed in this below-threshold regime, and it is not clear how to make use of them. In this talk, we present a generalization of the scattering formalism that resolves this issue, allowing one to also constrain scattering amplitudes on the $t$-channel cut.

hep-lat↗