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Light Resonances and the Low-$q^2$ Bin of $R_{K^*}$ by Altmannshofer, Wolfgang; Baker, Michael J.; Gori, Stefania; Harnik, Roni; Pospelov, Maxim; Stamou, Emmanuel; Thamm, Andrea is a scholarly article available to read on EtoBox.

What is Light Resonances and the Low-$q^2$ Bin of $R_{K^*}$ about?

LHCb has reported hints of lepton-flavor universality violation in the rare decays $B \to K^{(*)} \ell^+\ell^-$, both in high- and low-$q^2$ bins. Although the high-$q^2$ hint may be explained by new short-ranged interactions, the low-$q^2$ one cannot. We thus explore the possibility that the latter is explained by a new light resonance. We find that LHCb's central value of $R_{K^*}$ in the low-$q^2$ bin is achievable in a restricted parameter space of new-physics scenarios in which the new, light resonance decays preferentially to electrons and has a mass within approximately $10$ MeV of the di-muon threshold. Interestingly, such an explanation can have a kinematic origin and does not require a source of lepton-flavor universality violation. A model-independent prediction is a narrow peak in the differential $B \to K^* e^+e^-$ rate close to the di-muon threshold. If such a peak is observed, other observables, such as the differential $B \to K e^+e^-$ rate and $R_K$, may be employed to distinguish between models. However, if a low-mass resonance is not observed and the low-$q^2$ anomaly increases in significance, then the case for an experimental origin of the lepton-flavor univers

Author

Altmannshofer, Wolfgang; Baker, Michael J.; Gori, Stefania; Harnik, Roni; Pospelov, Maxim; Stamou, Emmanuel; Thamm, Andrea

Published

2017

Language

EN