TeV-scale string resonances at hadron colliders

Abstract

We construct tree-level four-particle open-string amplitudes relevant to dilepton and diphoton production at hadron colliders. We expand the amplitudes into string resonance (SR) contributions and compare the total cross-section through the first SR with the ${Z}^{\ensuremath{'}}$ search at the Tevatron. We establish a current lower bound based on the CDF Run I results on the string scale to be about $1.1\ensuremath{-}2.1$ TeV, and it can be improved to about $1.5\ensuremath{-}3$ TeV with 2 ${\mathrm{f}\mathrm{b}}^{\ensuremath{-}1}$. At the LHC, we investigate the properties of signals induced by string resonances in dilepton and diphoton processes. We demonstrate the unique aspects of SR-induced signals distinguishable from other new physics, such as the angular distributions and forward-backward asymmetry. A $95%$ C.L. lower bound can be reached at the LHC for ${M}_{S}>8.2\ensuremath{-}10$ TeV with an integrated luminosity of $300$ ${\mathrm{f}\mathrm{b}}^{\ensuremath{-}1}$. We emphasize the generic features and profound implications of the amplitude construction.