  To separate scintillation and Cherenkov lights in water-based liquid
scintillator detectors is a desired feature for future neutrino and proton
decay researches. Linear alkyl benzene (LAB) is one important ingredient of a
water-based liquid scintillator being developed. In this paper we observed a
good separation of scintillation and Cherenkov lights in an LAB sample. The
rising and decay times of the scintillation light of the LAB were measured to
be $(7.7\pm3.0)\ \rm{ns}$ and $(36.6\pm2.4)\ \rm{ns}$, respectively, while the
full width [-3$\sigma$, 3$\sigma$] of the Cherenkov light was 12 ns dominated
by the time resolution of our photomultiplier tubes. The light yield of the
scintillation was measured to be $(1.01\pm0.12)\times10^3\
\rm{photons}/\rm{MeV}$.
