Graviton production through photon-quark scattering at the LHC

TL;DR

This work analyzes real graviton production in ADD and RS extra-dimensional models through the LHC photoproduction channel $pp\to p\gamma p\to p G qX$. Using the equivalent photon approximation and folding subprocess cross sections $\sigma(\gamma q\to G q)$ with photon and quark distributions, the authors derive 95% CL bounds on ADD parameters $(M_D,\delta)$ and RS parameters $(m_G,\beta)$ for various luminosities and forward-detector acceptances, employing missing-energy signatures (ADD) or resonant decays $G\to \gamma\gamma,e^+e^-,\mu^+\mu^-$ (RS). They find ADD signals exhibit characteristic missing-$p_T$ and missing-$M_{Inv}$ spectra that enable background suppression and strong sensitivity, while RS constraints are generally weaker than current resonant searches. The study demonstrates the potential of forward-proton-tagged photoproduction as a powerful, complementary probe of TeV-scale gravity, especially for ADD, and emphasizes the universality of graviton couplings across channels. $(M_D,\delta)$ and $(m_G,\beta)$ parametrizations are central to the analysis, with $M_D$ controlling the KK tower density and $\beta$ setting the RS graviton mass scale.

Abstract

We have investigated real graviton emission in the ADD and RS model of extra dimensions through the photoproduction process pp-> p gamma p-> pGqX at the LHC. We have considered all contributions from the subprocesses gamma q -> G q, where q=u,d,c,s,b,anti-u,anti-d, anti-c, anti-s, anti-b quark. The constraints on model parameters of the ADD and RS model of extra dimensions have been calculated. During numerical calculations we have taken account of 3, 4, 5 and 6 large extra dimensional scenarios. The constraints on RS model parameters have been calculated by considering G -> gamma gamma, e^- e^+, mu^- mu^+ decay channels of the graviton.

Figures (12)

• Figure 1: The photoproduction process $pp\to p\gamma p\to p G qX$.
• Figure 2: Tree-level Feynman diagrams for the subprocess $\gamma q \to G q$ ($q=u,d,c,s,b,\bar{u},\bar{d}, \bar{c}, \bar{s}, \bar{b}$).
• Figure 3: The total cross section of the process $pp\to p\gamma p\to p G qX$ as a function of the fundamental scale $M_D$ for various number of extra dimensions $\delta$. The forward detector acceptance is chosen to be $0.0015<\xi<0.5$.
• Figure 4: The total cross section of the process $pp\to p\gamma p\to p G qX$ as a function of the fundamental scale $M_D$ for various number of extra dimensions $\delta$. The forward detector acceptance is chosen to be $0.0015<\xi<0.15$.
• Figure 5: The differential cross section of the process $pp\to p\gamma p\to p G qX$ as a function of the transverse momentum of the KK tower. The number of extra dimensions is chosen to be $\delta=3$ and $M_D=5$ TeV. In the left panel we present total cross section (solid line) which represents the sum of all contributions from subprocesses in (\ref{['subprocesses']}) and cross sections including individual contributions from each subprocess with quarks. In the right panel we present similar plots but for subprocesses with antiquarks.