v0.18

This first release in 2017 brings lots of new features and some bug fixes.

Several improvements have been made to probability distributions, which are required to quantify both theoretical and experimental uncertainties needed to compute prediction uncertainties and to construct likelihoods for fits:

• A new class GammaUpperLimit appropriate for low-statistics measurements resulting in an upper limit (e.g. on a rare decay branching ratio),
• A new class MultivariateNumericalDistribution that allows to specify any probability distribution in an arbitrary number of dimensions. This works with all the functions implemented, like computing uncertainties and Bayesian fits.
• Constraints in the form of a fixed range (uniform likelihood within and zero outside) can now be specified in YAML files in the intuitive form [0.1, 3.5].
• A new way of specifying arbitrary probability distributions in YAML files.

There is also a new page in the documentation about details on the treatment of probability distributions and how to define them in YAML. The API docs have been updated as well.

On the physics side, the following processes have been added:

• The forward-backward asymmetry in inclusive B→X_ql⁺l^- decays. Like The branching ratio added in v0.15, this is based on arXiv:1503.04849 and profited a lot from help by Tobias Huber.
• The branching ratio of B_c→lν.
• Lepton flavour ratios in B→Mlν decays, including experimental measurements of the μ/τ ratios in B→D^(*)lν.

Finally, the following bugs have been fixed:

• In the presence of new physics, the decay B_d→l⁺l^- erroneously used b→s Wilson coefficients. Thanks to @jackypheno (Jacky Kumar) for spotting and fixing this.
• Measurements with a Gaussian upper limit constraint returned the wrong likelihood if the confidence level specified was different from 68%.
• A glitch in the log-enhanced QED corrections to B→X_ql⁺l^- was fixed (the change is numerically irrelevant).