@freyablekman @CMSexperiment The figure suggests that the confidence region is azimuthally symmetric around the origin. Is it pure coincidence that the best fit is so close to the prediction or are things more constrained in the azimuthal direction than I am inferring?
@internic @CMSexperiment typically I recommend you actually read the paper for such technical questions. But the only assumption to the fit here is that they are coupled (eg sqrt(kappa-c^2 + kappa_b^2) = constant, so on an ellipse/circle). so yes, negative values are kind of allowed, if you look at the legend the difference in likelihood on the circle is pretty small.