Spin effects in the antler event topology at hadron colliders

We investigate spin correlation effects in the antler event topology pp -> A(*) -> B1B2 -> (l(-)C(1))(l(+)C(2)) at the LHC. We study the shapes of several kinematic variables, including the relative pseudorapidity, relative azimuthal angle and the energies of the two leptons, as well as several mass variables M-ll, M-eff, root s(min), M-T2, M-CT and M-CTx. We focus on the two kinematic extremes of root s - threshold and infinity - and derive analytical expressions for the differential distributions of several variables, most notably the cos theta(l-l+)* variable proposed by Barr in hep-ph/0511115. For all possible spin assignments of particles A, B and C, we derive the cos theta(l-l+)* differential distribution at threshold, including the effects of spin correlations. Our analytical results help identify the problematic cases for spin discrimination.