Scattering Massive String Resonances through Field-Theory Methods

TL;DR

This paper introduces a novel, exact method in string theory to compute tree-level amplitudes involving one massive state and any number of massless states, using a simplified heterotic string model.

Contribution

The authors develop a new approach that leverages the twisted heterotic string to explicitly compute mixed massive and massless string amplitudes at tree level.

Findings

Explicit formulas for amplitudes with one massive state

Mapping of heterotic string amplitudes to type-I and type-II superstrings

Method applicable to arbitrary numbers of massless states

Abstract

We present a new method, exact in $\alpha'$, to explicitly compute string tree-level amplitudes involving one massive state and any number of massless ones. This construction relies on the so-called twisted heterotic string, which admits only gauge multiplets, a gravitational multiplet, and a single massive supermultiplet in its spectrum. In this simplified model, we determine the moduli-space integrand of all amplitudes with one massive state using Berends-Giele currents of the gauge multiplet. These integrands are then straightforwardly mapped to gravitational amplitudes in the twisted heterotic string and to the corresponding massive amplitudes of the conventional type-I and type-II superstrings.