Fix: switching from eta to absolute eta in METSignificanceTool
This MR fixes a bug discovered by @hpacey: make the handling of pile-up uncertainties in the METSignificanceTool actually eta-symmetric by switching from eta to the absolute value of eta.
Tagging also @mswiatlo and @camacho.
We'd also like to sweep this into master, but I'm not sure which label I've to set for this. Could one of the shifters maybe help with that?
Thanks!
Michael
Edited by Michael Holzbock