Abstract
Following recent experimental developments, in this study we re-evaluate if the interplay of high- and low-energy lepton flavour violating observables remains a viable probe to test the high-scale type-I supersymmetric seesaw. Our analysis shows that fully constrained supersymmetric scenarios no longer allow to explore this interplay, since recent LHC data precludes the possibility of having sizeable slepton mass differences for a slepton spectrum sufficiently light to be produced, and in association to BR(μ → eγ) within experimental reach. However, relaxing the strict universality of supersymmetric soft-breaking terms and fully exploring heavy neutrino dynamics, still allows to have slepton mass splittings $ \mathcal{O}\left( {\mathrm{few}\;\%} \right) $ , for slepton masses accessible at the LHC, with associated μ → eγ rates within future sensitivity. For these scenarios, we illustrate how the correlation between high- and low-energy lepton flavour violating observables allows to probe the high-scale supersymmetric seesaw.
Highlights
The MEG experiment has significantly improved the upper bounds on BR(μ → eγ) [63]. In view of the latter developments, it is important to re-evaluate the prospects of probing the type-I SUSY seesaw via the synergy between slepton mass differences and low-energy sleptons may be discovered in tchLeFfVortohbcsoemrvianbgle√s ssu=ch as BR(μ → 14 TeV LHC
In this study we have revisited the impact of a type-I SUSY seesaw concerning LFV following the recent MEG bound on BR(μ → eγ), LHC data, and the measurement of θ13, updating the results obtained in [39]
The aim of our work was to discuss whether current cLFV results and SUSY searches still render viable the observation of slepton mass differences at the LHC, and if the interplay of the latter observables with low-energy cLFV bounds could still shed some light on the high-energy seesaw parameters
Summary
The type-I SUSY seesaw consists of the Minimal Supersymmetric Standard Model (MSSM), extended by three generations of right-handed neutrino (chiral) superfields Nic ∼ (νc, νR∗ )i. We work in a basis where both the charged lepton Yukawa couplings Y l and the Majorana mass matrix MR are diagonal. In the seesaw limit (i.e., Y νv2 ≪ MR), after electroweak (EW) symmetry breaking, the light neutrino mass matrix is approximately given by mν ≃ −v22Y νT MR−1Y ν, where v2 is one of the vacuum expectation values of the neutral Higgs Hi (v1(2) = v cos(sin)β, with v = 174 GeV). U MNS is the leptonic mixing matrix and R is a complex orthogonal matrix, parameterised in terms of three complex angles (θi), that encodes additional mixings involving the right-handed (RH) neutrinos; mdνiag and MRdiag respectively denote the (diagonal) light and heavy neutrino mass matrices
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