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Register a new userAxion-like particles resolve the $B to pi K$ and g-2 anomalies
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We offer a new solution to an old puzzle in the penguin-dominated $Btopi K$ decays. The puzzle is the inconsistency among the measurements of the branching ratios and CP asymmetries of the four $Btopi K$ decays: $B^+ to pi^+ K^0$, $B^+to pi^0 K^+$, $B_d^0topi^- K^+$, $B_d^0topi^0 K^0$. We solve the $Btopi K$ puzzle by considering the effect of an axion-like particle (ALP) that mixes with the $pi^0$ and has mass close to the $pi^0$ mass. We show that the ALP can also explain the anomalies in the electron and muon anomalous magnetic moments.
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Data from the Muon g-2 experiment and measurements of the fine structure constant suggest that the anomalous magnetic moments of the muon and electron are at odds with standard model expectations. We survey the ability of axion-like-particles, two-Higgs-doublet models and leptoquarks to explain the discrepancies. We find that accounting for other constraints, all scenarios except the Type-I, Type-II and Type-Y two-Higgs-doublet models fit the data well.
In the light of the recent result of the Muon g-2 experiment and the update on the test of lepton flavour universality $R_K$ published by the LHCb collaboration, we systematically build and discuss a set of models with minimal field content that can simultaneously give: (i) a thermal Dark Matter candidate; (ii) large loop contributions to $bto sellell$ processes able to address $R_K$ and the other $B$ anomalies; (iii) a natural solution to the muon $g-2$ discrepancy through chirally-enhanced contributions.
We perform a phenomenological analysis of simplified models of light, feebly interacting particles (FIPs) that can provide a combined explanation of the anomalies in $bto s l^+ l ^-$ transitions at LHCb and the anomalous magnetic moment of the muon. Different scenarios are categorised according to the explicit momentum dependence of the FIP coupling to the $b-s$ and $mu-mu$ vector currents and they are subject to several constraints from flavour and precision physics. We show that a phenomenologically viable combined solution to the muon $g-2$ and flavour anomalies always exists if a vector with mass larger than $4 ,textrm{GeV}$ is exchanged. Interestingly, the LHC has the potential to probe this region of the parameter space by increasing the precision of the $Zto 4mu$ cross-section measurement. Conversely, we find that solutions based on the exchange of a lighter vector, in the $m_V < 1,textrm{GeV}$ range, are essentially excluded by a combination of $Bto K +textrm{invisible}$ and $W$-decay precision bounds.
We present a model of radiative neutrino masses which also resolves anomalies reported in $B$-meson decays, $R_{D^{(star)}}$ and $R_{K^{(star)}}$, as well as in muon $g-2$ measurement, $Delta a_mu$. Neutrino masses arise in the model through loop diagrams involving TeV-scale leptoquark (LQ) scalars $R_2$ and $S_3$. Fits to neutrino oscillation parameters are obtained satisfying all flavor constraints which also explain the anomalies in $R_{D^{(star)}}$, $R_{K^{(star)}}$ and $Delta a_mu$ within $1, sigma$. An isospin-3/2 Higgs quadruplet plays a crucial role in generating neutrino masses; we point out that the doubly-charged scalar contained therein can be produced in the decays of the $S_3$ LQ, which enhances its reach to 1.1 (6.2) TeV at $sqrt s=14$ TeV high-luminosity LHC ($sqrt s=100$ TeV FCC-hh). We also present flavor-dependent upper limits on the Yukawa couplings of the LQs to the first two family fermions, arising from non-resonant dilepton ($pp rightarrow ell^+ ell^-$) processes mediated by $t$-channel LQ exchange, which for 1 TeV LQ mass, are found to be in the range $(0.15 - 0.36)$. These limits preclude any explanation of $R_{D^{(star)}}$ through LQ-mediated $B$-meson decays involving $ u_e$ or $ u_mu$ in the final state. We also find that the same Yukawa couplings responsible for the chirally-enhanced contribution to $Delta a_mu$ give rise to new contributions to the SM Higgs decays to muon and tau pairs, with the modifications to the corresponding branching ratios being at (2-6)% level, which could be tested at future hadron colliders, such as HL-LHC and FCC-hh.
We present a novel data-driven method for determining the hadronic interaction strengths of axion-like particles (ALPs) with QCD-scale masses. Using our method, it is possible to calculate the hadronic production and decay rates of ALPs, along with many of the largest ALP decay rate to exclusive final states. To illustrate the impact on QCD-scale ALP phenomenology, we consider the scenario where the ALP-gluon coupling is dominant over the ALP coupling to photons, electroweak bosons, and all fermions for $m_{pi} lesssim m_a lesssim 3$ GeV. We emphasize, however, that our method can easily be generalized to any set of ALP couplings to SM particles. Finally, using the approach developed here, we provide calculations for the branching fractions of $eta_c to VV$ decays, i.e. $eta_c$ decays into two vector mesons, which are consistent with the known experimental values.
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