Search for pair production of additional neutral scalars within the Inert Doublet Model in a final state with two electrons or two muons in proton-proton collisions at √s=13 TeV and 13.6 TeV

A bstract A first dedicated search for pair production of new scalars predicted by the Inert Doublet Model is performed using proton-proton collisions. Data were collected with the CMS detector at the CERN LHC at √s=13 TeV and 13.6 TeV, corresponding to integrated luminosities of 138 fb − 1 and 35 fb − 1 , respectively. Within this model, four additional scalar bosons (H, A, H + , and H − ) are predicted. Through an additional discrete symmetry, the lightest new scalar, H, is stable, rendering it a viable dark matter candidate. These candidates can originate from quark-antiquark annihilation producing an offshell Z boson that decays to a pair of the new scalars. The target final state consists of exactly two opposite-charge same-flavour leptons (electrons or muons), with missing transverse momentum due to the stable neutral scalars, and very little hadronic activity. A parameterised neural network is used to separate the signal from the standard model background. No significant excess of events is observed. Exclusion limits at 95% confidence level are set on the production cross section of the two new neutral scalars, H and A, expressed in terms of their masses, m H and m A , in the m H vs. m A − m H plane. The observed (expected) exclusion region reaches m H = 108 (106) GeV for m A − m H = 78 (76) GeV and at m H = 70 GeV, covers the range of m A − m H = 40–90 (35–90) GeV.