Limits on Low Scale Gravity from $e^+ e^- \to W^+ W^-, ZZ$ and $\gamma \gamma$

TL;DR

This paper investigates how virtual graviton exchange in low-scale gravity models affects certain collider processes, setting a lower limit of about 1 TeV on the string scale based on LEP2 data.

Contribution

It provides the first constraints on low-scale gravity models from $e^+ e^-$ collider processes involving gauge boson pair production.

Findings

LEP2 data constrains the string scale to approximately 1 TeV.

Virtual graviton exchange affects $e^+ e^- o W^+ W^-, ZZ, ext{and}\, \gamma \, ext{gamma}$.

Lower bounds on the quantum gravity scale are established.

Abstract

It has been proposed recently that the scale of quantum gravity (``the string scale'') can be $M_S \sim$ few TeV with $n \geq 2$ extra dimensions of size $R \stackrel{<}{\sim}$ mm so that, at distances greater than $R$, Newtonian gravity with $M_{Pl} \sim 10^{18}$ GeV is reproduced if $M_{Pl}^2 \sim R^n M_S^{n+2}$. Exchange of virtual gravitons in this theory generates higher-dimensional operators involving SM fields, suppressed by powers of $M_S$. We discuss constraints on this scenario from the contribution of these operators to the processes $e^+ e^- \to W^+ W^-, ZZ, \gamma \gamma$. We find that LEP2 can place a limit $M_S \approx 1$ TeV from $e^+ e^- \to W^+ W^-, ZZ, \gamma \gamma$.