Black Holes and Quantum Gravity at the LHC

TL;DR

This paper argues that thermal, multiparticle black hole signatures at the LHC are unlikely in most of the viable parameter space, and that a low-scale quantum gravity scenario is better probed through two-body final states and compositeness-type searches. By analyzing how near-threshold BH-like dynamics, string resonances, and higher-dimension gravity operators would modify 2→2 dijet and dilepton processes, the authors show that angular observables, especially the transversality ratio R_η, along with the energy dependence of dσ/dM, can distinguish among competing quantum gravity pictures. They provide concrete expectations for cross-section turn-ons near threshold, characteristic stringy dips and resonances, and four-fermion operator signatures, including leptonic channels that CMS and LHC data could probe up to tens of TeV scales. The work emphasizes that even without true thermal BH production, collider signals can reveal the nature of gravity in higher dimensions and help identify the underlying theory (BH, string, or higher-dimension operators) at TeV scales with practical experimental observables. The study thus reframes collider searches for quantum gravity from thermality-focused multiparticle bursts to incisive two-body signatures with robust discriminants.

Abstract

We argue that the highly studied black hole signatures based on thermal multiparticle final states are very unlikely and only occur in a very limited parameter regime if at all. However, we show that if the higher-dimensional quantum gravity scale is low, it should be possible to study quantum gravity in the context of higher dimensions through detailed compositeness-type searches.

Figures (16)

• Figure 1: Arbitrarily normalized parton-parton luminosity plot as a function of $\sqrt{\hat{s}}$ to show the relative contributions of initial state partons.
• Figure 2: Possible criteria for $x_{min}$ plotted as a function of $x_{min}$. ADD with n=6 is plotted on the left and RS is plotted on the right.
• Figure 3: From Fig.10 of Yoshino:2005hi. The ratio of the mass of the putative black hole compared to the initial energy of the collision is plotted as a function of the impact parameter divided by a unit $r_0$ that approximates the Schwarzschild radius if all the energy of the initial collision were to end up as a black hole. The lowest curve represents the calculation of Yoshino:2005hi, and previous estimates from Eardley:2002reYoshino:2002tx are also included.
• Figure 4: Total black hole cross section in femtobarns, including(solid curves) and not including(dashed) inelasticity as a function of $M_D$ for ADD with $n=6$ and $\tilde{M}$ for RS1. The different curves from highest to lowest correspond to $x_{min}=1-6$.
• Figure 5: In the upper plots curves of total cross section for having 6 or more particles, including(solid curves) and not including(dashed) inelasticity as a function of $M_D$ for ADD with $n=6$ and $\tilde{M}$ for RS1. The different curves from highest to lowest correspond to $x_{min}=1-6$. In the lower plots the same curves are plotted for having 2 particles instead of 6 or more.