Bulk physics at a graviton factory

A general prediction of the 5-d Randall–Sundrum (RS) hierarchy model is the emergence of spin-2 Kaluza–Klein (KK) gravitons with weak scale masses and couplings. The lowest order effective theory of the RS model is given by 5-d Einstein gravity which uniquely fixes the self-interactions of gravitons. We demonstrate that large numbers of light KK resonances could be produced at a future lepton-collider-based “Graviton Factory”. Measuring the self-interactions of these KK gravitons will probe the accuracy of the 5-d Einstein gravity picture and, in addition, yield indirect information on the as yet untested self-coupling of the 4-d graviton. The self-interactions of the gravitons can be studied by measuring the decays of the heavier states to the lighter ones. Using the AdS/CFT picture, these can be interpreted as the decays of heavier resonances to lighter ones, in a strongly coupled 4-d CFT. We show that these decays have sufficient rates to be studied at future colliders and that they are also, in principle, sensitive to higher derivative operators, such as the Gauss–Bonnet term. In a generalized RS model, with non-universal 5-d fermion masses, FCNCʹs will be induced. We show that precise measurements of the rare decays of KK graviton/gauge states into flavor non-diagonal final states at a Graviton Factory can be used to map the 5-d fermion mass matrix.