"Figure 9c" of "Search for W' bosons decaying to a top and a bottom quark in leptonic final states in proton-proton collisions at $\sqrt{s}$ = 13 TeV"

A search for W' bosons decaying to a top and a bottom quark in final states including electrons or muons is performed with the CMS detector at the LHC. The analyzed data correspond to an integrated luminosity of $138~\mathrm{fb}^{-1}$ of proton-proton collisions at a center-of-mass energy of $13~\mathrm{TeV}$. In general, good agreement with the standard model expectation is observed and no evidence for the existence of the W' boson is found over the mass range examined. The largest observed excess is found for a W' boson mass ($m_{\mathrm{W'}}$) hypothesis of $3.8~\mathrm{TeV}$ with a relative decay width of $1\%$, with a local (global) significance of $2.6$ $(2.0)$ standard deviations. Upper limits on the production cross sections of W' bosons decaying to a top and a bottom quark are set. Left- and right-handed W' bosons with $m_{\mathrm{W'}}$ below $3.9$ and $4.3~\mathrm{TeV}$, respectively, are excluded at the $95\%$ confidence level, under the assumption that the new particle has a narrow decay width. Limits are also set for relative decay widths up to $30\%$. These are the most stringent limits to date on W' bosons decaying to a top and a bottom quark.