Detection of two-photon exclusive production of supersymmetric pairs at the LHC

TL;DR

The paper investigates the potential of exclusive two-photon production at the LHC to detect supersymmetric particles, using forward-proton detectors to access photon energies and reconstruct event kinematics. By analyzing LM1, LM9, and Sweet Spot SUSY benchmarks, it demonstrates that sleptons and charginos can be discovered with favorable S/B for LM1, and that masses can be measured with a few GeV precision through W_gamma_gamma and W_miss based reconstructions, including an event-by-event method for light sleptons. In LM9, chargino production remains viable with optimized cuts that significantly suppress WW background, while Sweet Spot SUSY offers a direct path to stau mass and spin measurements via complete kinematic information of gamma-gamma events. Overall, photon-photon exclusive production provides a clean, complementary channel with powerful kinematic handles for SUSY searches, especially when high-resolution forward detectors are available at high luminosity.

Abstract

The detection of pairs of sleptons, charginos and charged higgs bosons produced via photon-photon fusion at the LHC is studied, assuming a couple of benchmark points of the MSSM model. Due to low cross sections, it requires large integrated luminosity, but thanks to the striking signature of these exclusive processes the backgrounds are low, and are well known. Very forward proton detectors can be used to measure the photon energies, allowing for direct determination of masses of the lightest SUSY particle, of selectrons and smuons with a few GeV resolution. Finally, the detection and mass measurement of quasi-stable particles predicted by the so-called sweet spot supersymmetry is discussed.

Figures (8)

• Figure 1: Most relevant Feynman diagrams for the MSSM analysis. Left: Chargino decay into a charged(neutral) scalar and a neutral(charged) fermion. Right: Slepton decay into a charged lepton and a LSP.
• Figure 2: Distribution of two-photon invariant mass $W_{\gamma \gamma}$ for the LM1 benchmark and integrated luminosity L = 100 fb$^{-1}$. Two visible peaks are due to production thresholds of $\tilde{\ell}_R^+\tilde{\ell}_R^-$ and $\tilde{\ell}_L^+\tilde{\ell}_L^-$ pairs. Verious contribution are added cumulatively. The background distribution of $WW$ pairs is shown separately, and is rescaled to obtain similar size as signal.
• Figure 3: Distribution of missing invariant mass $W_{miss}$ for the LM1 MSSM benchmark for the integrated luminosity L = 100 fb$^{-1}$. It starts at about $2~m_{LSP}$ for SUSY, at zero for the $WW$ background.
• Figure 4: Missing energy distribution for the LM1 benchmark and the $WW$ background for the integrated luminosity L = 100 fb$^{-1}$.
• Figure 5: Scatter plots for the LM1 signal and the $WW$ background on the $W_{miss}$, $W_{\gamma\gamma}$ plane. Upper: $\tilde{\mu}_R^+\tilde{\mu}_R^-$ events (orange/light) and $W^+W^-$ events (red/dark). Lower: $\tilde{\mu}_L^+\tilde{\mu}_L^-$ events (green/light) and $W^+W^-$ events (red/dark).