Open peterstangl opened 8 months ago
Is that beta from B to psi KS or something else?
It's mostly $B\to\psi K_S$ but also some other charmonium channels listed here: https://hflav-eos.web.cern.ch/hflav-eos/triangle/latest/#sin2b
But then it's no longer a tree-level determination, so not appropriate to use it in presence of dim-6 NP, or not?
But shouldn't the question be whether there might be a potential dim-6 NP contribution affecting the extraction of the CKM parameter, rather than whether the process is tree or loop level? Of course, in general, loop-level processes might be more affected by dim-6 NP than tree-level ones, but there is no real guarantee of that, right? And at the moment there are tensions in tree-level $b\to u\ell\nu$ data that could be interpreted in terms of dim-6 NP (e.g. https://arxiv.org/abs/2302.05268).
So, in the end, don't we always have to choose which dim-6 NP contributions we assume to be absent when extracting the CKM elements as used in the current implementation in flavio? And I'm not sure the absence of NP in tree-level $b\to u\ell\nu$ is necessarily better motivated than its absence in loop-level $B$ mixing.
In the end, could it make sense to implement the CKM extraction in the presence of dim-6 NP that we have in smelli
in flavio
to avoid this problem no matter whether tree or loop level observables are used?
This PR changes the default CKM scheme to the
beta gamma
scheme, which, compared to theTree
scheme, uses the UT angle $\beta$ instead of $|V{ub}|$. The advantage is that this input scheme is unaffected by the tension between inclusive and exclusive $|V{ub}|$ determinations (and the tensions between different exclusive determinations). Furthermore, with the most recent determination of $\beta$, the precision of the CKM elements is increased. The predicted value of $|V{ub}|$ in this scheme with the currentflavio
inputs is $$|V{ub}|=(3.72\pm0.09)\times 10^{-3}\,,$$ which has an error nearly two times smaller than the exclusive $V_{ub}$ determined from $B\to\pi\ell\nu$.