LFV and Leptogenesis inSUSY models

Martti RaidalNICPB, Tallinn

“Mass Origin and SUSY”, TsukubaMarch 6-8

07.03.2006 Mass Origin and SUSY 2

Outline

• Introduction• LFV in SUSY seesaw and leptogenesis• Parameterization appropriate for LFV• Flavour and Leptogenesis• Conclusions

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Motivations

• LF exactly conserved in the SM

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• However, LF is violated in the Nature!Light neutrinos are massive and mix!

• Light neutrino mixing alone impliesnegligible LFV rates of charged leptons

• To observe LFV decays of chargedleptons, New Physics not far from theEW scale must exist.

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• Natural candidate is SUSY

• SUSY Flavour and CP problem• Predictive scheme for LFV: MSSM+ NR

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• SUSY seesaw model

9 par. 18 par.

RRT=1

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• Renormalization of Yν induces off-diagonal soft terms below 1 TeV

• Implies observable BR of LFV decays ofcharged leptons

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• Density perturbations observed by WMAP

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Baryogenesis via Leptogenesis

Sakharov:• B violation• C and CP violation• Out-of-equilibrium conditions

Yanagida:• B-L violation• Sphalerons

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washout effects calculable• Seesaw and thermal leptogenesis are

consistent• For hierarchical MN , MN1>109 GeV• For degenerate MN f(x) exhibits a resonance

behaviour

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Roadmap of SUSY Seesaw phenomenology

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Phenomenological analyses of LFV

• Fix the measured neutrino parameters• Generate all the rest, including the

parameter matrix R randomly• Assume values of the universal soft

terms• Typical result: bound on µ→eγ implies

small LFV tau lepton decays

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Parametrization of seesaw suitable forstudies of LFV

• Assume Hermitian parameter matrix H• Identify H with• Solve• Choose required H

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Observation of LFV in τ decays possible

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Flavoured Leptogenesis

• An idea: create out-of-equilibriumcondition for one flavour only 1/3B-Lτ

• Requires flavour symmetries

Yν = MN degenerate

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Predictions of tau leptogenesis

• Inversely hierarchical light neutrinomass spectrum

• Observable BR(µ→eγ), suppressedBR(τ→µγ)

• Ni can be very light, observable atcollider experiments

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Predictions of e-Leptogenesis

• Normally ordered light neutrino massspectrum

• Large BR(τ→µγ), suppressedBR(µ→e γ)

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Conclusions

• Searches for LFV decays of chargedleptons give info SUSY and seesaw

• Exist parameterizations and models inwhich τ LFV is large, µ LFV suppressed

• Leptogenesis constraint in generalenhances LFV rates (large Yukawas)

• Possibility of flavoured leptogenesis