Connecting Particle Physics and Cosmology: Measuring the Dark Matter Relic Density in Compressed Supersymmetry at the LHC

TL;DR

This paper proposes methods to measure the dark matter relic density at the LHC within compressed supersymmetry models, linking collider data to cosmological dark matter abundance with a 25% uncertainty.

Contribution

It introduces two collider search strategies (VBF and ISR) to determine the dark matter relic density in compressed SUSY scenarios, a novel approach connecting collider measurements to cosmological parameters.

Findings

Relic density can be measured with 25% uncertainty at the LHC.

VBF and ISR searches effectively probe the coannihilation region.

Method applicable to models where coannihilation reduces dark matter abundance.

Abstract

The identity of Dark Matter (DM) is one of the most captivating topics in particle physics today. The R-parity conserving Minimal Supersymmetric Standard Model (MSSM), which naturally provides a DM candidate in the form of the lightest neutralino ($\tilde{\chi}_{1}^{0}$), is used as a benchmark scenario to show that a measurement of $\Omega_{\tilde{\chi}_{1}^{0}}h^{2}$ can be achieved from measurements at the CERN Large Hadron Collider. Focus is placed on compressed mass spectra regions, where the mass difference between the $\tilde{\chi}_{1}^{0}$ and the $\tilde{\tau}_{1}$ is small and where the $\tilde{\tau}_{1}$-$\tilde{\chi}_{1}^{0}$ coannihilation (CA) mechanism of the early Universe plays an important role. The technique for measuring $\Omega_{\tilde{\chi}_{1}^{0}}h^{2}$ relies on two proposed searches for compressed Supersymmetry (SUSY): 1) production via Vector Boson Fusion (VBF) processes; and 2) production with associated energetic jets from initial state radiation (ISR). These approaches allow for the determination of the relic abundance at the LHC for any model where CA is an important DM reduction mechanism in the early Universe. Thus, it is possible to confirm that the DM we observe today were $\tilde{\chi}_{1}^{0}$'s created in the early Universe. We show that from measurements in the VBF and ISR SUSY searches at the LHC, the dark matter relic density can be measured with an uncertainty of 25\% with 3000 fb$^{-1}$ of 13 TeV proton-proton data.