Amplitude analysis of the Tcc+ observation using two-channel S-matrix

Abstract

Different amplitude analyses have contradicting interpretations on the nature of the doubly-charmed tetraquark T_cc⁺. This state emerges as a peak in the D⁰D⁰π⁺ invariant mass in pp collisions. This may decay into the D^*+D⁰ channel, and its peak lies just below this channel's energy. This means that the usual Breit-Wigner amplitude is less accurate in the amplitude analysis because of the coupled channel effects. We use the two-channel uniformized S-Matrix to generate the scattering amplitude. We manually fit this line shape to the experiment's D⁰D⁰π⁺ invariant mass distribution. We generate and compare two cross sections with the first having a one-pole configuration and the second with two-pole configuration. It was found that the one-pole configuration had a better fit (χ²/d.o.f. = 1.50) than the two-pole configuration (χ²/d.o.f. = 2.25), which gives a molecular interpretation of the T_cc⁺. Moreover, we recommend in the future to automate the fitting and consider higher numbers of poles using machine learning.