Searching solo for the invisible at Compact Muon Solenoid (CMS)

Abstract

Despite the success of the Standard Model (SM), several fundamental questions remain unanswered, such as the nature of dark matter (DM), motivating searches for new physics. This paper summarizes three recent searches for new physics in proton-proton collisions at a center-of-mass energy of $\sqrt{s}=13$ TeV, using data recorded with the Compact Muon Solenoid (CMS) detector at the CERN Large Hadron Collider (LHC). The searches focus on "mono-X" final states, characterized by a large imbalance in transverse momentum recoiling against a single visible SM particle ($X$), and serve as powerful probes of new physics scenarios. Results are presented for searches in the pencil-jet (low-multiplicity jet), mono-photon, and mono-top final states, using CMS Run 2 data corresponding to an integrated luminosity of 138 fb$^{-1}$. No significant excess of events beyond SM predictions is observed, and the results are used to set stringent exclusion limits on various new physics scenarios, including simplified DM models and models of large extra spacetime dimensions.

Figures (12)

• Figure 1: An example of a mono-X event, recorded by the CMS detector.
• Figure 2: Representative leading order Feynman diagram of the signal process, where $\chi$ is the DM candidate, V/A represents the vector or axial vector mediator, $g_q$ and $g_{DM}$ represents the mediator coupling to the quarks and DM respectively. Due to the low mass of the Z' boson ($\approx 1 ~$ GeV), it primarily decays to a low multiplicity final state, typically two pions.
• Figure 3: Distinguishing features of a pencil-jet against the standard hadronic $\tau$ and QCD jets.
• Figure 4: Distinguishing features of a pencil-jet against the standard hadronic $\tau$ and QCD jets.
• Figure 5: Postfit plots showing the data-simulation agreement for 2016 (left), 2017 (middle), and 2018 (right).