Direct Production of Lightest Regge Resonances

TL;DR

This work develops a direct collider-facing framework for Regge excitations in open string theories with D-branes, constructing covariant vertex operators for the universal first massive level that survive generic Calabi–Yau compactifications. By computing helicity-resolved amplitudes for one massive Regge state plus up to three massless partons, the authors derive explicit two- and three-body decay channels and, crucially, parton-level cross sections for LHC-relevant production channels: gluon fusion, gluon–quark absorption, and quark–antiquark annihilation, with comprehensive monodromy-based relations and normalization checks. The results identify the universally observable resonances (notably the spin-2 $B(J=2)$ and scalar $\Phi(J=0)$) and provide a complete set of helicity amplitudes and cross sections in terms of the string scale $M$ ($M^2=1/\alpha'$) and the invariant variables $s,t,u$, offering model-independent collider signatures for low-mass string scenarios. These findings advance string phenomenology by delivering ready-to-use predictions for direct Regge resonance production at the LHC and clarifying how universal Regge states manifest across CY compactifications. The work also clarifies the role of boundary-changing operators for quark excitations and the interplay between SUSY currents and string excitations in shaping observable decay channels.

Abstract

We discuss direct production of Regge excitations in the collisions of massless four-dimensional superstring states, focusing on the first excited level of open strings ending on D-branes extending into higher dimensions. We construct covariant vertex operators and identify ``universal'' Regge states with the internal parts either trivial or determined by the world-sheet SCFT describing superstrings propagating on an arbitrary Calabi-Yau manifold. We evaluate the amplitudes involving one such massive state and up to three massless ones and express them in the helicity basis. The most important phenomenological applications of our results are in the context of low-mass string (and large extra dimensions) scenarios in which excited string states are expected to be produced at the LHC as soon as the string mass threshold is reached in the center-of-mass energies of the colliding partons. In order to facilitate the use of partonic cross sections, we evaluate them and tabulate for all production processes: gluon fusion, quark absorbing a gluon, quark-antiquark annihilation and quark-quark scattering.

Figures (1)

• Figure 1: Factorization of four--gluon amplitude into pairs of two three--point couplings.