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Abstract:The recently proposed "mini-seesaw mechanism" combines naturally suppressed Dirac and Majorana masses to achieve light Standard Model neutrinos via a lowscale seesaw. A key feature of this approach is the presence of multiple light (order GeV) sterile-neutrinos that mix with the Standard Model. In this work we study the bounds on these light sterile-neutrinos from processes like µ → e+ γ, invisible Z-decays, and neutrinoless double beta-decay. We show that viable parameter space exists and that, interestingly, key observables can lie just below current experimental sensitivities. In particular, a motivated region of parameter space predicts a µ → e + γ branching fraction within the range to be probed by MEG.

Section: Fcnc Bounds: µ → E + γmentioning

confidence: 99%

Neutrino mass and μ → e + γ from a mini-seesaw

Duerr

George

McDonald

2011

“…In each panel, the blue lines denote BR(µ → eγ) isolines: the former MEGA bound, 1.2 × 10 −11 [81] (lower dashed line), the MEG current bound 5.7 × 10 −13 [63] [59][60][61][62]. Figure 1 clearly manifests the effect of the new BR(µ → eγ) upperlimit, which in all cases amounts to dramatically reducing the previously allowed cMSSM SUSY-seesaw space.…”

Section: Jhep01(2014)015mentioning

confidence: 99%

Slepton mass splittings and cLFV in the SUSY seesaw in the light of recent experimental results

Figueiredo

Teixeira

2014

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 O(few %), 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.

“…At the two-loop level, we find the stronger constraint M T > ∼ 5 × 10 8 GeV. We have explored the parameter space for this scenario, taking into account the bounds on the lightest Higgs mass m h [101] and on rare LFV decays [102][103][104]. The outcome is a certain tension between these constraints and that on perturbative gauge coupling unification.…”

Section: Phenomenological Viability Mssm Spectrum and Lhc Searchesmentioning

confidence: 99%

Beyond the standard seesaw: neutrino masses from Kähler operators and broken supersymmetry

Brignole

Joaquim

Rossi

2010

We investigate supersymmetric scenarios in which neutrino masses are generated by effective d = 6 operators in the Kähler potential, rather than by the standard d = 5 superpotential operator. First, we discuss some general features of such effective operators, also including SUSY-breaking insertions, and compute the relevant renormalization group equations. Contributions to neutrino masses arise at low energy both at the tree level and through finite threshold corrections. In the second part we present simple explicit realizations in which those Kähler operators arise by integrating out heavy SU(2) W triplets, as in the type II seesaw. Distinct scenarios emerge, depending on the mechanism and the scale of SUSY-breaking mediation. In particular, we propose an appealing and economical picture in which the heavy seesaw mediators are also messengers of SUSY breaking. In this case, strong correlations exist among neutrino parameters, sparticle and Higgs masses, as well as lepton flavour violating processes. Hence, this scenario can be tested at highenergy colliders, such as the LHC, and at lower energy experiments that measure neutrino parameters or search for rare lepton decays.