Wei Chao Center for High Energy Physics, PKU

1. TeV Seesaw Models and Possible Collider Signatures Wei Chao Center for High Energy Physics, PKU 2009. 09. 14 Chao, Si, Zheng and Zhou, arXiv: 0907.0935[hep-ph]

2. “Grand unified” neutrino spectrum in the universe

3. p, He … , K    Evidence for neutrino oscillation （Ashieet al., PRL 04）  oscillation decay decoherence Confirmed by K2Kand MINOS.

4. Evidence for Neutrino Oscillations Confirmed by KamLAND

5. Neutrino Masses and Mixing angles Standard Parameterization: Neutrino oscillation parameters Harrison et al., 02; Xing , 02.

6. Neutrino mass models • Masses for Charged Fermions: • Higgs Mechanism; • Yukawa Interactions. • No right-handed neutrinos; • Only one Higgs doublet; • No non-renormalizable terms. • Mν=0； • Global U(1)3 flavor symmetry: Le, Lμ，Lτ .

7. Dirac VS Majorana Extra dimension Seesaw mechanism;radiativecorrections. Conserve L ; violate Le ，Lμ，Lτ. Violate L， Le ，Lμ，Lτ。

8. Radiative corrections Singly charged scalar singlet + scalar doublet Babu（88） Zee（80） Two scalar singlets Ma （98） Higgs doublet + right-handed Majorana neutrinos + Z2

9. Seesaw mechanisms SU(2)LFermion singlet Minkowski（77） SU(2)L scalar triplet Magg， Wetterich（80） SU(2) Lfermion triplet Foot，Lew， He，Joshi（89）

10. Integrating out heavy Particles ν mass term Kinematic term NC • Non-unitary • Zero-distance effect • New CP-violating phases CC

11. TeV Seesaw Models: 1. natural one Inverse seesaw model: SM+6 gauge singlets Full Lagrangian The only term that breaks lepton number explicitly; when μ=0 the lepton number is conserved . Light Neutrino mass matrix:

12. Charged current interactions: Effective lepton mixing matrix: Scale of unitarity violation: Dirac neutrinos when μ=0: Pseudo-Dirac neutrinos: Collider Signatures for heavy particles: √ ×

13. TeV Seesaw Models: 2. unnatural one Dirac neutrino mass matrix and masses of heavy Majorana neutrinos have the following relationship: Buchmueller, Greub（91）… Mν=0 at the tree level Non-zero neutrino masses come from perturbative effects or one loop radiative corrections:

14. Conventional type-I seesaw TeV –scale seesaw model 1015 GeV 1 TeV 10-2 eV 10-2 eV 100 GeV 100 GeV Unitarity violation for MNS matrix:10-2 Unitarity violation for MNS matrix:10-26 Big enough

15. A realistic TeV-scale seesaw model SM + I Higgs triplet + 2 right-handed Majorana neutrinos: Conventional type-I seesaw mechanism （1） 0 + small Conventional type I+II seesaw mechanism （2） small + small Similar to type-II seesaw mechanism （3） small + 0 Type-II term : responsible for generating neutrino masses Type-I term: totally structure cancellation leading to appreciable collider signatures Big numbers cancellation （4） big — big

16. Symmetry of the model: Flavor symmetry Full Lagrangian

17. Mass Matrix for charged leptons: Neutrino mass matrices:

18. In assumption that v1=v2=v3, charged lepton mass matrix can be written as Setting u1=u3=0: Neutrino masses:

19. Collider Signatures for heavy Majorana neutrinos σ∝ |R|4, highly suppressed σ∝ |R|2 ·BR, N Produced on resonance • Two heavy Majorana neutrinos !

20. Numerical results 3•2 complex matrix R can be parameterized by 6 rotation angles and 6 phases ---Xing, PLB 2008 Antush, et al JHEP 06 A typical input : |R ei|2=1.25 ×10-7; |Rμi|2=|RƮi|2=5 ×10-3

24. Concluding remarks • A mini review on neutrino mass models. • A realistic TeV scale seesaw model is proposed. • Collider signatures of heavy Majorana neutrinos • are discussed. • Further work is necessary to construct a natural • and testable neutrino mass model. 谢谢