Angular dependence of PMT efficiency

The quantum efficiency ×capture efficiency of the PMT can have an angular dependence – see slide 6 of this talk (at 5th HK proto-collaboration meeting, password required).

So far, this was apparently not used for energy reconstruction in SK. Once we have measured this effect for the new Hyper-K PMTs, that should probably be added a separate correction. (For clarity’s sake, it’s probably better not to combine it with the angular dependency of the photocoverage in issue #7.)