Abstract
A global fit to the recent B->K*mu+mu- data shows indications for a large new-physics contribution to the Wilson coefficient of the semi-leptonic vector operator. In this article we consider a simple Z'-boson model of 3-3-1 type that can accommodate such an effect without violating any other constraint from quark-flavour physics. Implications for yet unobserved decay modes such as B->Xsnunubar and longstanding puzzles like B->piK are also discussed. The Z'-boson masses required to address the observed anomaly lie in the range of 7 TeV. Such heavy Z' bosons evade the existing bounds from precision data and direct searches, and will remain difficult to discover even at a high-luminosity LHC. The potential of an ILC as well as the next generation of low-energy parity-violation experiments in constraining the Z'-boson parameter space is also examined.
Highlights
Not provide a unique best solution, a simple scenario of new physics emerges as a possible explanation, that features the following modifications of Wilson coefficients [7]1
Data from LHCb alone, whereas [8] incorporates the available results from ATLAS, BaBar, Belle, CDF and CMS; for what concerns the low-q2 region the work [7] considers the bins [0.1, 2] GeV2, [2, 4.3] GeV2 and [4.3, 8.68] GeV2, while the authors of [8] perform averages to obtain values for the observables integrated over the [1, 6] GeV2 bin. These differences in combination with the fact that the most significant deviation of 3.7σ appears in P5 in the interval [4.3, 8.68] GeV2 [1, 2] explains why, in contrast to [7], the article [8] finds that a new-physics contribution ∆C9 ∼ −1.5 alone does not lead to a good description of the data
We argued above that the treatment of B → Xs + − in the global fit is likely to have an important impact on the physics implications of the B → K∗μ+μ− anomaly
Summary
Note that we do not consider the right-handed Z -boson couplings to the SM quarks since it is always possible to make these interactions flavour diagonal by an appropriate choice of quantum numbers. The flavour-changing quark interactions can be confined to the sector of downtype quarks by choosing Uu = 1 (or equivalently Ud = V ), i.e. by alignment in the up-type quark sector. The flavourchanging interactions will necessarily have a non-trivial structure when there are gauge quantum numbers that distinguish generations This is the case in Z -boson models of the. For other common choices of β (i.e. 3, ±1/ 3) this is not the case, which renders these models uninteresting for our purposes
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