  A search is presented for charged, long-lived supersymmetric particles in
final states with one or more disappearing tracks. The search is based on data
from proton-proton collisions at a center-of-mass energy of 13 TeV collected
with the CMS detector at the CERN LHC between 2016 and 2018, corresponding to
an integrated luminosity of 137 fb$^{-1}$. The search is performed over final
states characterized by varying numbers of jets, b-tagged jets, electrons, and
muons. The length of signal-candidate tracks in the plane perpendicular to the
beam axis is used to characterize the lifetimes of wino- and higgsino-like
charginos produced in the context of the minimal supersymmetric standard model.
The d$E$/d$x$ energy loss of signal-candidate tracks is used to increase the
sensitivity to charginos with a large mass and thus a small Lorentz boost. The
observed results are found to be statistically consistent with the
background-only hypothesis. Limits on the pair production cross section of
gluinos and squarks are presented in the framework of simplified models of
supersymmetric particle production and decay, and for electroweakino production
based on models of wino and higgsino dark matter. The limits presented are the
most stringent to date for scenarios with light third-generation squarks and a
wino- or higgsino-like dark matter candidate capable of explaining the known
dark matter relic density.
