Diagnosing lepton-nonuniversality in b → sℓℓ

By G. Hiller, M. Schmaltz. 2014

153 citations recorded by the source corpus.

A bstractRatios of branching fractions of semileptonic B decays, (B → Hμμ) over (B → Hee) with H = K, K∗, Xs, K0(1430), ϕ, . . . are sensitive probes of lepton universality. In the Standard Model, the underlying flavor changing neutral current process b → sℓℓ is lepton flavor universal. However models with new flavor violating physics above the weak scale can give substantial non-universal contributions. The leading contributions from such new physics can be parametrized by effective dimension six operators involving left- or right-handed quarks. We show that in the double ratios RXs/RK$$ {R_X}_{{}_s}/{R}_K $$, RK ∗/RK and Rϕ/RK the dependence on new physics coupling to left-handed quarks cancels out. Thus a measurement of any of these double ratios is a clean probe of flavor nonuniversal physics coupling to right-handed quarks. We also point out that the observables RXs$$ {R_X}_{{}_s} $$, RK ∗, RK01430$$ {R}_K{{}_{{}_0}}_{(1430)} $$ and Rϕ depend on the same combination of Wilson coefficients and therefore satisfy simple consistency relations.

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/5bd1b21e536f1f419818256a3cb49ce6316bdf2b

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Citations in the corpus

Flavour anomalies after the RK∗ measurement (2017, background): “86 is the “polarization fraction” [24, 27, 28], that is defined as”
Rare $B$ Decays as Tests of the Standard Model (2016, background): “w to disentangle a QCD eect from a possible new physics contribution [333,334]. If the new physics contribution is not lepton avour universal, measurements of ratios of b!se+e and b!s+ observables [193,335] represent theoretically clean ways to unambiguously identify it, since a possible hadronic ee”
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Physics of leptoquarks in precision experiments and at particle colliders (2016, methodology): “ed by resorting to LFU ratios, as in e.g. RK ( B !K+ [)=( B !Ke+e ) 78], where experimental and theoretical uncertainties are signiﬁcantly reduced. For recent works addressing the RK observablecf.[138,96,90,99,120,119,77,97,91]. Finally, decays with a vector meson P !V‘+‘ in the ﬁnal state are effe”
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