Dear all, Clem, thanks for this excellent summary. For those who have not heard all the calls, I wanted to add my concurrence to this summary and to the proposed actions which we've discussed extensively now on- and off-line. But we should solicit full comment from the collaboration at this point--please weigh in. As an aside, although Clem describes this situation as unfortunate it strikes me how much I would rather be in our shoes--having an experiment that concentrates sensitivity enough to identify and study anomalies at relatively high S/N when they rise to a level that could impact our result--than an experiment that spreads sensitivity across more sky where to reach similar levels we'd have to assure ourselves that we can rule out effects that are tiny compared to our noise. The recent efforts to understand the false signal by isolating the inconsistent modes are encouraging and should continue to be pushed. Until we reach such understanding, we have an upper-limits-only experiment, so we must push on. Regarding our policy on looking at results, some have wanted clarification so let me lay out how I see our general approach: We do deliberate, cautious, coordinated analysis. We proceed at each step of the analysis in a deliberate way, asking as a collaboration whether looking at the answer from our actual data could prejudice analysis choices not yet made. We do not do "blind analysis". Some physicists have very specific ideas about what blind analysis means and I personally agree with those who say that trying to rigidly map that framework onto CMB analysis makes you *more* likely to miss real problems in your data and so screw up. We should probably avoid casual use of loaded terms like "unblinding" and "opening the box"--let's all attempt to be more disciplined about that going forward. When we choose to calculate a specific statistic on the actual non-jack data, that is how we should describe it. The key to our ethics is that we are deliberate in proceeding on those steps that involve looking at answers. For the present case, I would emphasize that we do fail an internal consistency test--BICEP2 vs. Keck--a powerful test but a harder one to work with than our usual jacks. As Clem says, for 4 months now we have searched without success to find a BICEP2-only jackknife that fails as obviously. Our motivation for doing this, without first looking at the BICEP2 B bandpowers, was to preserve prospects for a quick BICEP2-only path to a result we can believe to be "clean". But after 4 months, I feel that now even if we had the a-ha insight into the origin of this false-B next week and could propose a fix, we ourselves probably would not be convinced any remaining B signal in BICEP2 is celestial without invoking consistency tests with Keck data. As we decide now to take the step of directly comparing power in jack0 BICEP2 and Keck B-modes (we have been visually comparing their patterns for some time), I'd say (1) that the path forward to understanding this effect requires that we use all the information available to us, (2) that once we have such understanding, trust in our post-fix data being clean is probably going to have to involve checking consistency between BICEP2 and Keck, (3) that we are interested in the short term in seeing what immediate upper limits on the combination of actual B signal and correlated noise/systematics the combination of BICEP2 and Keck data can give us. Any correlation will be a valuable diagnostic; reliable upper limits will be a valuable result. John On 3/26/13 5:29 PM, Clem Pryke wrote: -- ___________________________________________________________________ John Kovac jmkovac(a)cfa.harvard.edu Assistant Professor, Astronomy and Physics, Harvard University 160 Concord Ave rm 310, Cambridge MA 02138, 617-496-0611