We consider Z2-symmetric braneworlds arising from 5-sphere compactifications with
5-form flux in type IIB supergravity. This Kaluza-Klein reduction produces a D = 5
theory which supports 1
2
-supersymmetric Z2-symmetric domain-wall solutions. However, upon lifting such solutions back to D = 10, one finds that supersymmetry is
broken by 5-sphere Kaluza-Klein effects. This happens owing to the action on the
Killing spinor of the Z2 ⊂ SO(1, 9) symmetry, which requires an orientation-reversing
transformation in the 5-sphere directions together with the flip of the orbifold coordinate. We study the consequences of this supersymmetry breaking for the masses of
fermion fluctuation modes about the brane background and find a natural two-scale
hierarchy: some bulk modes have characteristic masses of order 1
L5
but other modes
more closely associated to the branes have an additional factor exp(−
ρ
L5
), where L5 is
the AdS5 length parameter and ρ is the orbifold size.