We report on a search for charged massive long-lived particles (CMLLPs), based on 5.2 fb−1 of integrated luminosity collected with the D0 detector at the Fermilab Tevatron p¯p collider. We search for events in which one or more particles are reconstructed as muons but have speed and ionization energy loss (dE/dx) inconsistent with muons produced in beam collisions. CMLLPs are predicted in several theories of physics beyond the standard model. We exclude pair-produced long-lived gauginolike charginos below 267 GeV and Higgsino-like charginos below 217 GeV at 95% C.L., as well as long-lived scalar top quarks with mass below 285 GeV.Received 17 October 2011DOI:https://doi.org/10.1103/PhysRevLett.108.121802© 2012 American Physical Society