Analysis of rescattering effects in $$3\pi $$ final states
Dominik Stamen, Tobias Isken, Bastian Kubis, M. Mikhasenko, Malwin Niehus
Abstract
Abstract Decays into three particles are often described in terms of two-body resonances and a non-interacting spectator particle. To go beyond this simplest isobar model, crossed-channel rescattering effects need to be accounted for. We quantify the importance of these rescattering effects in three-pion systems for different decay masses and angular-momentum quantum numbers. We provide amplitude decompositions for four decay processes with total $$J^{PC} = 0^{--}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mi>J</mml:mi> <mml:mrow> <mml:mi>PC</mml:mi> </mml:mrow> </mml:msup> <mml:mo>=</mml:mo> <mml:msup> <mml:mn>0</mml:mn> <mml:mrow> <mml:mo>-</mml:mo> <mml:mo>-</mml:mo> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> , $$1^{--}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mn>1</mml:mn> <mml:mrow> <mml:mo>-</mml:mo> <mml:mo>-</mml:mo> </mml:mrow> </mml:msup> </mml:math> , $$1^{-+}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mn>1</mml:mn> <mml:mrow> <mml:mo>-</mml:mo> <mml:mo>+</mml:mo> </mml:mrow> </mml:msup> </mml:math> , and $$2^{++}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mn>2</mml:mn> <mml:mrow> <mml:mo>+</mml:mo> <mml:mo>+</mml:mo> </mml:mrow> </mml:msup> </mml:math> , all of which decay predominantly as $$\rho \pi $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>ρ</mml:mi> <mml:mi>π</mml:mi> </mml:mrow> </mml:math> states. Two-pion rescattering is described in terms of an Omnès function, which incorporates the $$\rho $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>ρ</mml:mi> </mml:math> resonance. Inclusion of crossed-channel effects is achieved by solving the Khuri–Treiman integral equations. The unbinned log-likelihood estimator is used to determine the significance of the rescattering effects beyond two-body resonances; we compute the minimum number of events necessary to unambiguously find these in future Dalitz-plot analyses. Kinematic effects that enhance or dilute the rescattering are identified for the selected set of quantum numbers and various masses.