$$b\rightarrow s\ell ^+\ell ^-$$ global fits after $$R_{K_S}$$ and $$R_{K^{*+}}$$

Abstract

We present an up-to-date complete model-independent global fit to $$b\rightarrow s\ell \ell $$ b → s ℓ ℓ observables that confirms patterns of New Physics able to explain the data. We include the recent LHCb measurements of $$R_K$$ R K , $$R_{K_S}$$ R K S , $$R_{K^{*+}}$$ R K ∗ + , $$B_s \rightarrow \phi \mu ^+\mu ^-$$ B s → ϕ μ + μ - and $$B_s\rightarrow \mu ^+\mu ^-$$ B s → μ + μ - in our analysis, which now includes 254 observables. This updates our previous analyses and strengthens their two main outcomes. First, the presence of right-handed couplings encoded in the Wilson coefficients $${{\mathcal {C}}}_{9'\mu }$$ C 9 ′ μ and $${{\mathcal {C}}}_{10'\mu }$$ C 10 ′ μ remains a viable possibility. Second, a lepton flavour universality violating (LFUV) left-handed lepton coupling ($${{\mathcal {C}}}_{9\mu }^{\mathrm{V}}=-{{\mathcal {C}}}_{10\mu }^{\mathrm{V}}$$ C 9 μ V = - C 10 μ V ), often preferred from the model building point of view, accommodates the data better if lepton-flavour universal New Physics is allowed, in particular in $${{\mathcal {C}}}_{9}^{\mathrm{U}}$$ C 9 U . We observe that the LFUV observable $$Q_5$$ Q 5 offers a very interesting possibility to separate both types of scenarios.

Explaining the hints for lepton flavour universality violation with three S2 leptoquark generations

“…Regarding b → s + − , an excellent fit to data can be obtained in new physics scenarios featuring an LFU C U 9 effect in addition to a LFUV violating effect C µ 9 = −C µ 10 [247,248]. In fact, this scenario even constitutes the two-dimensional one which gives the best fit to data [25]. This is precisely the setup realised in the considered model with three generations of LQs, in which the photon penguin contribution induced by the presence of the tauquark is combined with the W -box contribution involving the muoquark, so that C µ 9 = −C µ 10 .…”

“…This makes a discovery at the LHC possible, and an observation at future colliders even guaranteed. In particular, measurements of b → s + − [5][6][7][8][9][10][11][12][13][14][15][16] and b → cτ ν [17][18][19][20][21][22] observables deviate from their corresponding SM predictions by more than 7 σ [23][24][25][26][27][28][29][30][31] (this tension being reduced to 4−5σ when including only LFUV observables [23][24][25][26]32]) and by more than 3 σ [33] respectively. Moreover, measurements of the anomalous magnetic moment of the muon (g−2) µ [34,35] are known to deviate from the SM predictions by more than 4 σ when following the community consensus [36].…”

Beyond the Standard Model with Lepton Flavor Universality Violation

“…In fact, including all observables into a global fit [20][21][22], one finds that several NP scenarios, possessing destructive NP w.r.t. the SM at the 20% level, are preferred over the SM hypothesis by more than 7σ [23] (see also Refs. [?, ?, ?, ?…”

New Physics in $b \to s μμ$: FCC-hh or a Muon Collider?

“…The anomalous observables include: branching ratios [110][111][112][113][114][115][116]; angular distributions [117,118]; and the theoretically very clean [119][120][121] LFU ratios, R K ( * ) [3,4]. When interpreting all of the data in a low-energy effective field theory, a consistent picture of NP emerges (for recent global fits see [122][123][124][125][126][127][128][129]). The global significance of the NP hypothesis, including the lookelsewhere effect, was conservatively estimated to be 4.3σ [130].…”