This Feynman diagram illustrates the interaction of two Kaluza-Klein particles with modes \( n \) and \( m \), which you can define. Modes represent the quantized momentum states of particles in extra dimensions, determining their mass and behavior in our four-dimensional world. The diagram shows two incoming particles (with modes \( n \) and \( m \)) interacting at a vertex to produce a third particle with mode \( - (n + m) \). Arrows indicate the direction of particle flow. By adjusting the input values for \( n \) and \( m \), you can explore how different mode combinations affect the outgoing particle's mode.