  Production of a single top quark provides excellent opportunity for
understanding top quark physics and Cabibbo-Kobayashi-Maskawa structure of the
quark sector in the Standard Model. Although an associated production with a
b-quark has already been observed at the Tevatron in 2009, a single top
production in association with a W gauge boson has not been observed till 2014
at the LHC, where pair production of the top quark serves as the dominant
background. Due to the kinematic similarity between tW and the dominant
background, it is challenging to find suitable kinematic variables that offer
good signal-background separation, which naturally leads to the use of
multivariate methods. In this paper, we investigate kinematic structure of tW+j
channel using M_T2 and invariant mass variables, and find that tW +j production
could well be separated from tt production with high purity at a low cost of
statistics when utilizing these kinematic correlations.
