No certainty yet about the validity of the BICEP2's 2014 discovery
Two or three days before the preprint will appear on the arXiv, BICEP2/KeckArray have released their joint analysis with Planck:
The new joint paper is framed as a discovery of the B-modes at 7 standard deviations but these B-modes are presented as "dust and gravitational waves combined". This literally means that all probabilities of their model are obtained as sums (integrals, the so-called marginalization) over models with all possible values of the tensor-to-scalar ratio, \(r\).
When the high-depth, window-only BICEP2 data are mixed with the low-depth, global Planck data – just like if you dilute your favorite whisky in water at a 100-to-1 ratio, it becomes impossible to discover the primordial gravitational waves separately, the paper confirms. Instead, one may impose one of the usual Planck-like upper bounds on \(r\), namely \(r\lt 0.12\) at the 95% confidence level. This is slightly higher – more signal-like – than all the previous upper bounds coming from Planck.