Interpreting hints for lepton flavor universality violation

By W. Altmannshofer, P. Stangl, David M. Straub. 2017

300 citations recorded by the source corpus.

We interpret the recent hints for lepton flavor universality violation in rare $B$ meson decays. Based on a model-independent effective Hamiltonian approach, we determine regions of new physics parameter space that give a good description of the experimental data on $R_K$ and $R_{K^*}$, which is in tension with Standard Model predictions. We suggest further measurements that can help narrowing down viable new physics explanations. We stress that the measured values of $R_K$ and $R_{K^*}$ are fully compatible with new physics explanations of other anomalies in rare $B$ meson decays based on the $b \to s \mu\mu$ transition. If the hints for lepton flavor universality violation are first signs of new physics, perturbative unitarity implies new phenomena below a scale of $\sim 100$ TeV.

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/667be1e2a6f4a84bacb04685b6cd0013ed48a762

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In Nuclear and High Energy Physics

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Opportunities in Flavour Physics at the HL-LHC and HE-LHC (2018, background): “The HL-LHC and the capabilities of LHCb Upgrade II offer a unique opportunity to take another stride forward in precision for these quantities.”
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Review of lepton universality tests in B decays (2018, methodology): “eracy between NP contributions in b!s+ and b!se+e for LU observables is lifted once separate b!s+ and b!se+e observables are included (in particular angular observables). Recent combined analyses [126,127,153,162] single out some NP scenarios preferred over the SM with a signicance at the 5˙level, c”
Continuing search for new physics in b → sμμ decays: two operators at a time (2019, methodology): “After the advent of the RK∗ result in 2017, several analyses were performed with an aim of identifying the Lorentz structure of possible NP [27, 33–40].”
B →P and B →V form factors from B-meson light-cone sum rules beyond leading twist (2018, background): “Several studies [82–92] come to the conclusion that a negative shift to the short-distance coupling C 9 , and potentially to some couplings that vanish in the SM, can explain simultaneously the deviations in all anomalous b → s`+`− measurements; see [2] for a recent review and the definition of the ”
B-decay discrepancies after Moriond 2019 (2019, result): “ist of observables and measurements included, we refer the reader to [47]. Here we highlight the changes in observables sensitive to b!stransitions included with respect to the recent global analyses [29,30] by some of us. We include the LHCb update of R K [41] and the new, preliminary measurement o”
Physics case for an LHCb Upgrade II - Opportunities in flavour physics, and beyond, in the HL-LHC era (2018, unknown): “2 Search for D → hμ+μ− and Λ+c → pμ+μ− decays As already stated b→ s`+`− electroweak penguin transitions have proven to be powerful tools to search for New Physics effects [310,311].”