Crossposts are ok for me, but please cross reference the posts so a helper can check the progress.
Henri Menke already solved your problem, it was a missing pair of braces (C_{\hat{\imath}}). His tip of using imath to produce a dotless i is a very good one. He made some more improvements to your code, for example setting »numSeqNoise« upright in the first line and including the binary oparator > in the math-environment. Otherwise it is a textual > with the corresponding spacing which wouldn't make much sense.
You might even want to typeset the OR upright and maybe even bold.