We investigate brane in
ation driven by two stacks of mobile branes in a throat. The stack closest to the
bottom of the throat annihilates first with antibranes, resulting in particle production and a change of the
equation of state parameter w. We calculate analytically some observable signatures of the collision; related
decays are common in multield in
ation, providing the motivation for this case study. The discontinuity in
w enters the matching conditions relating perturbations in the remaining degree of freedom before and after
the collision, aecting the powerspectrum of curvature perturbations. We nd an oscillatory modulation of
the power spectrum for scales within the horizon at the time of the collision, and a slightly redder spectrum
on superhorizon scales. We comment on implications for staggered infation.
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