  In top squark (stop) searches with a compressed spectrum, it is very helpful
to consider the stop production recoiling against a hard jet from the initial
state radiation to obtain a significant amount of missing transverse energy. In
particular, the kinematic variable $R_M$ which measures the ratio of the
lightest neutralino mass and the stop mass proved to be crucial in separating
the signals from the backgrounds in both the all-hadronic decay and the
semileptonic decay of the stops. Here we generalize the search method to the
dileptonic stop decays. In this case, due to the two missing neutrinos, there
are not enough kinematic constraint equations to solve for the $R_M$ variable
exactly, but only render an allowed interval consistent with the event.
However, we show that the minimum and the maximum values of this allowed
interval still provide useful variables in discriminating signals from the
backgrounds. Although in the traditional stop decay to a top quark and the
lightest neutralino, the dileptonic mode is not as competitive due to its small
branching ratio, it becomes the main search mode if the stops decay through the
charginos and sleptons with a compressed spectrum. We show that with the new
variables, the dileptonic search of the stop can cover regions of the parameter
space which have not been constrained before.
