Probing new physics in diphoton production with proton tagging at the Large Hadron Collider

Abstract

The sensitivities to anomalous quartic photon couplings at the Large Hadron Collider are estimated using diphoton production via photon fusion. The tagging of the protons proves to be a very powerful tool to suppress the background and unprecedented sensitivities down to $6 \cdot 10^{-15}$\gev$^{-4}$ are obtained, providing a new window on extra dimensions and strongly-interacting composite states in the multi-TeV range. Generic contributions to quartic photon couplings from charged and neutral particles with arbitrary spin are also presented.

Figures (3)

• Figure 1: Diphoton production via photon fusion sensitive to $4\gamma$ anomalous couplings. Both protons are intact in the final state.
• Figure 2: Diphoton invariant mass distribution for the signal ($\zeta_{1} = 10^{-12},~10^{-13}$ GeV$^{-4}$, see Eq. \ref{['zetas']}) and for the backgrounds (dominated by $\gamma\gamma$ with protons from pile-up), requesting two protons in the forward detectors and two photons of $p_{\mathrm{T}} > 50$ GeV with at least one converted photon in the central detector, for a luminosity of 300$~\mathrm{fb}^{-1}$ and an average pile-up of $\mu = 50$. Excl. stands for exclusive backgrounds and DPE for double pomeron exchange backgrounds (see text).
• Figure 3: Diphoton to missing proton mass ratio (left) and rapidity difference (right) distributions for signal considering two different coupling values ($10^{-12}$ and $10^{-13}$ GeV$^{-4}$, see Eq. \ref{['zetas']}) and for backgrounds after requirements on photon $p_{\mathrm{T}}$, diphoton invariant mass, $p_{\mathrm{T}}$ ratio between the two photons and on the angle between the two photons. At least one converted photon is required. The integrated luminosity is 300 $\mathrm{fb}^{-1}$ and the average pile-up is $\mu=50$.