Disappearing Tracks from Electroweak Vector Dark Matter at the LHC

We study the disappearing-track signature of a spin-1 minimal dark matter candidate transforming in the real five-dimensional representation of $SU(2{)}_L$ with vanishing hypercharge. Radiative electroweak corrections induce a compressed mass spectrum among the multiplet components, allowing the singly charged state $V^{\pm }$ to attain a macroscopic lifetime and decay via $V^{\pm }\to V^0{\pi }^{\pm }$ inside tracking detectors. We recast the ATLAS search for disappearing tracks with the full Run-2 dataset of $137{\text{ fb}}^{-1}$, originally targeted at long-lived charginos, computing the tracklet reconstruction probability analytically from the published efficiency so that the full lifetime range is covered. The procedure reproduces the ATLAS limits for pure winos within $6\mathrm{\%}$ in mass. The Run-2 data exclude quintuplet masses up to $1080\text{ GeV}$ for proper decay lengths $c\tau \simeq 250\text{ mm}$, and $M_V<630\text{ GeV}$ for a mass splitting of $166\text{ MeV}$. For the radiative mass splitting predicted by the model with a small Higgs-portal coupling, masses between $120\text{ GeV}$ and $240\text{–}300\text{ GeV}$ are excluded. With $3{\text{ ab}}^{-1}$ and a Run-2-like analysis, the sensitivity would extend to $1750\text{ GeV}$ for vanishing background and to $1530\text{ GeV}$ for a linear extrapolation of the instrumental background.