Abstract
We study an extension of the Standard Model that addresses the hints of lepton flavour universality violation observed in Brightarrow K^{(*)} l^+l^- decays at LHCb, while providing a viable candidate for dark matter. The model incorporates two new scalar fields and a Majorana fermion that induce one-loop contributions to B meson decays. We show that agreement with observational data requires the new couplings to be complex and that the Majorana fermion can reproduce the observed dark matter relic density. This combination of cosmological and flavour constraints sets an upper limit on the dark matter and mediator masses. We have studied LHC dijet and dilepton searches, finding that they rule out large regions of parameter space by setting lower bounds on the dark matter and mediator masses. In particular, dilepton bounds are much more constraining in a future high-luminosity phase. Finally, we have computed the scattering cross section of dark matter off nuclei and compared it to the sensitivity of current and future direct detection experiments, showing that parts of the parameter space could be accessible in the future to multi-ton experiments. Future collider and direct DM searches complement each other to probe large areas of the parameter space of this model.
Highlights
LHCb has reported anomalies in the measured decay rates of the B meson, which have been interpreted as hints of lepton flavour universality violation [1,2]
The main production channel is the pair production of the coloured scalar particles, that subsequently decays into a dark matter (DM) particle and a quark, we study the experimental signatures that this model would produce at the LHC
Constraints from LHC searches for the four benchmark points defined in Sect. 2.3 are presented in Fig. 6 on the plane, for all the points that satisfy the flavour constraints of Sect. 2.2 and that reproduce the correct DM relic abundance
Summary
LHCb has reported anomalies in the measured decay rates of the B meson, which have been interpreted as hints of lepton flavour universality violation [1,2]. The SM predicts equal rates for the processes B → K (∗)μ+μ− and B → K (∗)e+e−, and it is customary to study the ratios of these branching ratios, defined as R(K ) and R(K ∗), since the dependencies on hadronic matrix elements (and associated uncertainties) cancel out [3]. The measurements of these hadronically clean observables deviate consistently ( perhaps with not enough statistical significance). 2, we introduce the details of the particle physics model, address the constraints from the observed DM relic abundance and Bs−mixing and discuss the implications on the model’s parameter space.
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