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Title: Scattering amplitudes and contour deformations
Authors: Eichmann, Gernot
Duarte, Pedro
Peña, M. T.
Stadler, Alfred
Keywords: Scattering amplitudes
Bethe-Salpeter equation
Bound states
Nonperturbative effects in quantum field theory
Issue Date: 1-Nov-2019
Publisher: American Physical Society
Citation: Gernot Eichmann, Pedro Duarte, M. T. Peña, and Alfred Stadler, "Scattering amplitudes and contour deformations", Physical Review D 100, 094001 (2019)
Abstract: We employ a scalar model to exemplify the use of contour deformations when solving Lorentz-invariant integral equations for scattering amplitudes. In particular, we calculate the onshell 2→2 scattering amplitude for the scalar system. The integrals produce branch cuts in the complex plane of the integrand which prohibit a naive Euclidean integration path. By employing contour deformations, we can also access the kinematical regions associated with the scattering amplitude in Minkowski space. We show that in principle a homogeneous Bethe-Salpeter equation, together with analytic continuation methods such as the Resonances-via-Padé method, is sufficient to determine the resonance pole locations on the second Riemann sheet. However, the scalar model investigated here does not produce resonance poles above threshold but instead virtual states on the real axis of the second sheet, which pose difficulties for analytic continuation methods. To address this, we calculate the scattering amplitude on the second sheet directly using the two-body unitarity relation which follows from the scattering equation.
Type: article
Appears in Collections:FIS - Publicações - Artigos em Revistas Internacionais Com Arbitragem Científica

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