Loopy Determinations of $V_{ub}$ and $V_{cb}$

Abstract

We use loop induced processes like meson oscillations and rare b hadron decays to determine the absolute values of the CKM matrix elements $|V_{ub}|$ and $|V_{cb}|$ and compare our results to the standard determinations based on inclusive and exclusive semileptonic tree-level decays of B mesons. For many years there have been tensions between the inclusive and exclusive determinations. Assuming the absence of new physics, we find that meson oscillation data shows a slight preference for the inclusive value of $|V_{cb}|$ and the exclusive value for $|V_{ub}|$. Rare b decay data prefers values for $|V_{cb}|$ far below the inclusive and exclusive determinations, offering a new perspective on some of the persistent rare b decay anomalies.

23 pages, 4 figures. v2: references added; updated numerics with latest B mixing lattice results; conclusions unchanged

References in corpus (10)

• Correlations among new CP violating effects in Delta F = 2 observables
• $B\to \pi \ell \nu$ and $B_s\to K\ell \nu$ form factors and $|V_{ub}|$ from 2+1-flavor lattice QCD with domain-wall light quarks and relativistic heavy quarks
• Bs mixing observables and Vtd/Vts from sum rules
• Three loop calculations and inclusive $V_{cb}$
• Can the differences in the determinations of $V_{ub}$ and $V_{cb}$ be explained by New Physics?
• $B_s\to K\ell \nu$ form factors from lattice QCD
• Inclusive semi-leptonic decays from lattice QCD
• Tension in the inclusive versus exclusive determinations of $|V_{cb}|$: a possible role of new physics
• First observation of the decay $B_s^0\to K^{-}{\mu }^{+}{\nu }_{\mu }$ and a measurement of $|V_{ub}|/|V_{cb}|$
• New ways to search for right-handed current in B -> rho ell nu decay