Measurement of the $${B} _{c} ^+$$ B c + meson lifetime using $${B} _{c} ^+ \rightarrow {{J} /\psi } \mu ^+ \upnu _\mu X$$ B c + → J / ψ μ + ν μ X decays

The lifetime of the $B_c^+$ meson is measured using semileptonic decays having a $J\!/\!\psi$ meson and a muon in the final state. The data, corresponding to an integrated luminosity of $2\mathrm{~fb^{-1}}$, are collected by the LHCb detector in $pp$ collisions at a centre-of-mass energy of $8\,\mathrm{TeV}$. The measured lifetime is $$\tau = 509 \pm 8 \pm 12 \mathrm{~fs},$$ where the first uncertainty is statistical and the second is systematic.