We investigate spin correlation effects in the "antler" event topology pp-> A-> B1, B2 -> l^{ -}, C1, l^{ +}, C2 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}, Meff, \sqrt{ s}_{ min}, MT2, MCT and MCTx. We focus on the two kinematic extremes of \sqrt{ s} - threshold and infinity - and derive analytical expressions for the differential distributions of several variables, most notably the cos{ \theta_{ ll}}^* variable proposed by Barr in hep-ph/0511115. For all possible spin assignments of particles A, B and C, we derive the cos{ \theta_{ ll}}^* differential distribution at threshold, including the effects of spin correlations. Our analytical results help identify the problematic cases for spin discrimination.
Categories: hep-ph