On the existence of angular correlations in decays with heavy matter partners

If heavy partners of the Standard Model matter fields are discovered at theLHC it will be imperative to determine their spin in order to uncover theunderlying theory. In decay chains, both the spin and the mass hierarchy of allparticles involved can influence the resulting angular correlations. We presentthe necessary conditions for decays involving the matter partners to exhibitangular correlations. In particular we find that when the masses are notdegenerate, a heavy fermionic sector always displays angular correlations incascade decays. When the masses are closely degenerate the size of spin effectsis controlled by a global phase parameter. In a large region of the parameterspace, correlations are strongly suppressed. In other regions, such as in UEDmodel where this phase is fixed by 5-d Lorentz invariance, the correlations arepronounced. In addition, we show that in certain cases one may even have enoughinformation to determine the spin of other heavy partners involved in the decay(such as the Lightest Stable Partner or a heavy gluon).Comment: 16 pages, 5 figures and 1 table, typos correcte