University College London. Frank Deppisch. University College London

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1 Frank Deppisch University College ondon Flavour Physics Conference Quy Nhon 7/01-0/08/014

2 Neutrinoless double beta decay μ e γ μ + e conversion in nuclei Δ e =, Δ μ = 0, Δ = epton Number Violation Δ e = 1, Δ μ = 1, Δ = 0 epton Flavour Violation Δ e = 1, Δ μ = 1, Δ = epton Flavour Violation + epton Number Violation / 14 Frank Deppisch Charged FV BSModels 31/07/014

3 Charged epton Flavour (practically) conserved in the SM (+ light ν) FV is clear sign for BSM physics Br μ eγ = 3α 3π i U μi U ei Δm 1i m W Flavour violation in the quark and neutrino sector Strong case to look for CFV Generic BSModels at TeV scale with couplings to leptons lead to large CFV CFV can shed light on Grand Unification models Flavour symmetries Origin of flavour 3 / 14 Frank Deppisch Charged FV BSModels 31/07/014

4 Models of Neutrino Mass Generation around the TeV scale Seesaw Models I, II, III, Inverse etc. Radiative Mass Models Zee, Babu-Zee, etc. Supersymmetry R-Parity Conserving Arbitrary slepton masses or in combination with high-scale Seesaw R-Parity Violating -violating couplings, Neutrino mass generation Extended iggs/gauge Sectors eft-right Symmetry, ittle iggs, Additional Doublets, etc. Extra Dimensions etc. 4 / 14 Frank Deppisch Charged FV BSModels 31/07/014

5 Models excite different (combinations of) operators de Gouvea, Vogel 13 μeγ μeqq μeγ μeee 5 / 14 Frank Deppisch Charged FV BSModels 31/07/014

6 Stringent limits on NP operators, e.g. Br l i l j γ 4 π3 α G 3 F m li 4 C M ij NP Br μ eγ < C μe < M NP TeV Br τ lγ < C τl < M NP TeV, l = e, μ FV couplings must be suppressed and/or New Physics scale is larger 10 3 TeV Solutions No New Physics at the TeV scale Specific flavour structure of New Physics Degeneracy Symmetry (e.g. Minimal Flavour Violation) 6 / 14 Frank Deppisch Charged FV BSModels 31/07/014

7 Effective operator for Majorana neutrino mass Only dimension-5 operator beyond SM 1 h ij Λ NV i c T j 1 m ν ijν i c ν j Seesaw Mechanism Add right-handed neutrinos N i to SM Y ij ν N i j 1 M ijn i N j c μ M N 1 (Y ki ν M 1 kl Y ν lj ) c i T j ight neutrino mass m ν 0.1 ev Y ν 100 GeV GeV M Y ν N Y ν 7 / 14 Frank Deppisch Charged FV BSModels 31/07/014

8 CFV in the Seesaw Mechanism ight neutrino exchange Negligible due to small neutrino masses and unitarity of PMNS mixing matrix Br μ eγ = 3α 3π i U μi U ei Δm 1i m W eavy neutrino exchange Sizable for TeV scale heavy neutrinos and large R mixing V R 10 Br μ eγ V R μi V R ei G i V R 10 4 m N i m W U ν = U (V R ) U R V R 8 / 14 Frank Deppisch Charged FV BSModels 31/07/014

9 Correct light neutrino masses for TeV scale heavy neutrinos Seesaw Mechanism with TeV scale heavy neutrinos Standard Seesaw with small Yukawa couplings CFV remains small Bent Seesaw mechanisms M = Decouple Λ NV from heavy neutrino mass Example 0 Y ν 0 Y ν μ M 0 M μ Potentially large CFV In the limit μ 0, no NV but CFV Y ν = 10 GeV M = 10 3 GeV Quasi-Dirac Majorana Neutrinos V R Y ν 10 6 m ν = 0.1 ev M N /TeV 9 / 14 Frank Deppisch Charged FV BSModels 31/07/014

10 Effective operator for Majorana neutrino mass Only dimension-5 operator beyond SM 1 h ij Λ NV i c T j 1 m ν ijν i c ν j Seesaw Mechanism Seesaw I Seesaw II Seesaw III Singlet Triplet Y ν Y ν Triplet Y ν Y ν Y 3 10 / 14 Frank Deppisch Charged FV BSModels 31/07/014

11 Effective operator for Majorana neutrino mass Only dimension-5 operator beyond SM 1 h ij Λ NV i c T j 1 m ν ijν i c ν j Radiative Generation via oops Alternative to Seesaw, e.g. Babu-Zee model (Zee 85, Babu 88) f Neutrino masses suppressed at -loop m g g h m k m f k 11 / 14 m Frank Deppisch Charged FV BSModels h 31/07/014

12 Neutrino flavour mixing radiatively induces slepton flavour mixing (Borzumati, Masiero 86) Correlation between slepton and neutrino flavour mixing (Type I) δm = δ 11 δ 1 δ 13 δ 1 δ δ 3 Y ν Y ν log(m X /M νr ) δ 33 δ 13 δ 3 Induces observable charged FV rates despite high scale Seesaw M νr GeV Type III Type II Type I Esteves et al / 14 Frank Deppisch Charged FV BSModels 31/07/014

13 τμ/τe flavour transitions less constrained (h μτ observed?) Small CFV messenger mass splitting Off-shell GIM mechanism Br(μ eγ) ΔM N /M WR σ C ΔM N /(M N Γ N ) CFV through heavy portal (FFD, Desai, Valle, Phys. Rev. D ) N can only decay through heavy-light suppressed coupling θ = Y ν /m N On-shell (resonant) GIM mechanism 13 / 14 Frank Deppisch Charged FV BSModels 31/07/014

14 FV is crucial probe for BSM physics Smoking gun for BSM physics Strong experimental sensitivity Λ TeV Connection to neutrino physics But possibly indirect (NV vs FV) Models of neutrino mass predict wildly different CFV rates CFV as discriminator τ lγ vs μ eγ vs μ e conversion vs μ eee μ e conversion in different nuclei Flavour Symmetries and Structures Discrete, Continuous, Textures, Minimal Flavour Violation CFV critical to solve flavour puzzle Synergy with C searches Potential to observe CFV (Already seen in h μτ?) Complementarity of Observables 14 / 14 Frank Deppisch Charged FV BSModels 31/07/014