Search for direct production of GeV-scale resonances decaying to a pair of muons in proton-proton collisions at $ \sqrt{s} $ = 13 TeV

A search for direct production of low-mass dimuon resonances is performed
using √s = 13 TeV proton-proton collision data collected by the CMS experiment during
the 2017–2018 operation of the CERN LHC with an integrated luminosity of 96.6 fb$^{−1}$. The
search exploits a dedicated high-rate trigger stream that records events with two muons
with transverse momenta as low as 3 GeV but does not include the full event informa-
tion. The search is performed by looking for narrow peaks in the dimuon mass spectrum
in the ranges of 1.1–2.6 GeV and 4.2–7.9 GeV. No significant excess of events above the
expectation from the standard model background is observed. Model-independent limits
on production rates of dimuon resonances within the experimental fiducial acceptance are
set. Competitive or world’s best limits are set at 90% confidence level for a minimal dark
photon model and for a scenario with two Higgs doublets and an extra complex scalar
singlet (2HDM+S). Values of the squared kinetic mixing coefficient ε$^2$ in the dark photon
model above 10$^{−6}$ are excluded over most of the mass range of the search. In the 2HDM+S,
values of the mixing angle sin(θH) above 0.08 are excluded over most of the mass range of
... mehr
the search with a fixed ratio of the Higgs doublets vacuum expectation tan β = 0.5.