Leptogenesis and Triplet Seesaw

Nov.9, 2006, SNU Leptogenesis & Triplet Seesaw

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Leptogenesis and Triplet Seesaw

Eung Jin ChunKIAS

Based on hep-ph/0609259 in collaboration with S. Scopel


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Matter-Antimatter asymmetry of the universe

• No antimatter around us.• Observation: • Asymmetrical initial condition after bigbang?• Generation of the asymmetry starting from matter

-antimatter symmetrical universe: “baryogenesis”• Sakharov condition: (1967) B or L violation

C and CP violation

Out of equilibrium


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Electroweak Spharelon Processes

B & L are conserved classically in SM.

Invariant under 6-3=3 U(1) symmetries

SU(3)c £ SU(2)L £ U(1)Y


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Electroweak Spharelon Processes

B+L is anomalous under SU(2)L

and thus broken by quantum effect.Efficient spharelon transitions at T>MW.


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Equilibrium distributions of charge asymmetries

• Equilibirum number densities:

• For T À m, • For T ¿ m• Charge asymmetry in X:

FD

BE

for FD/BE


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• B & L asymmetry:

• Spharelon erasure: B = L=3

• Gauge charge neutrality:


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• All gauge and Yukawas in equilibrium:

• Initial asymmety in transfers to B/L:


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Leptogenesis and Neutrino masses

Neutrino masses observed: Majorana nature of the small mass from

L violation: Requires new particles as the source of L violatio

n at high scale. Heavy particle decay falls into out-of-equilibrium f

or T<MX prohibiting inverse decays. Provided a nontrivial CP phase in the decay, a co

smological L asymmetry may arise as required by the observation.


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Leptogenesis in Singlet Seesaw Seesaw through singlet RHNs with heavy Majorana masses:

RHN decay produces CP/L asymmetry: tree+loop interference with CP phase in Yukawas


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Leptogenesis in Singlet Seesaw

CP asymmetry in RHN decay:

for M2,3 À M1

with eff·1


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Boltzmann equation:Inverse decay effective for KÀ1


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Approximate solution:Damping factor by inverse decay:

Cosmological lepton asymmetry:

ID=H


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Leptogenesis in Triplet Seesaw

• Supersymmetric Higgs Triplets with Y=1,-1

• Neutrino mass via seesaw in VEV:

• Triplet decays produce L asymmetry:


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• Boltzmann Equations

Gauge annihilation: * WW :


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• Decay vs. Annihilation:

• Leptogenesis Phenomenology with 5 independent parameters:


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Amount of CP violation required by observation in SM with only two channles: X LL, HH

Efficience increases far away from BL=BH=1/2


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Role of the third channel X H1 H1 in SUSY


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Lepton asymmetry generation with vanishing L


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Features with slow & fast for slow (Ki ¿ 1) & fast (Ki À 1) channel.slow=1: Efficiency reaches maximum.Inverse decays in the slow channel freeze out early, and annihilations determine the triplet density up to quite large mass M.The final asymmetry is a growing function of K parameter and is insensitive to fast. Even L=fast=0 can lead to efficient leptogenesis.

slow and one slow channel: The final lepton asymmetry is suppressed.Inverse decays freeze out late (zf» ln K À1), and decay is typically dominant over annihilation except for very small M. As a consequence, the efficiency scales as 1/(zf K) with K À1.


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slow<1 and two slow channels: The slow channel with large i drives leptogenesis with a good efficienc

y. The system is practically with two decay channels as in SM. If slow=L,2, the phenomenology is different from SM case because K no

w is much bigger, reducing the efficiency at high masses and improving it at lower ones.

Features with slow & fast for

slow (Ki ¿ 1) & fast (Ki À 1) channel.


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Conclusion

• Matter-Antimatter asymmetry of the Universe requires New Physics: B/L violation, new CP phase.

• It may have the same origin as the neutrino mass generation.

• Revelation of such connection in the future experiments?

• Successful leptogenesis can be attained in a wide range of scenarios in supersymmetric triplet seesaw model.

Documents

Leptogenesis and Triplet Seesaw