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TeV Seesaws and Non-unitary  -oscillations

Hi, I am a theorist ….  H. Murayama (SUSY08). Zhi-zhong Xing ( 邢志忠 ) IHEP, Beijing. TeV Seesaws and Non-unitary  -oscillations. Galaxies. Sun. Reactors. Elusive Neutrinos. Supernovae. They are everywhere; They are abundant; They are almost massless;

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TeV Seesaws and Non-unitary  -oscillations

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  1. Hi, I am a theorist …..  H. Murayama (SUSY08) Zhi-zhong Xing (邢志忠) IHEP, Beijing TeV Seesaws and Non-unitary -oscillations

  2. Galaxies Sun Reactors ElusiveNeutrinos Supernovae They are everywhere; They are abundant; They are almost massless; They travel almost at the speed of light; They are very very shy; …… Ourselves They are fundamentally important; They might allow you to touch NP! (NP=New PhysicsorNobel Prize) Accelerators Big Bang Earth

  3. > 20 000 Papers Golden time (2) Koshiba 87 Golden time (1) ?? EXAMPLES: 1956 discovery of ’s 1968 solar  anomaly 1987 supernova ’s 1998 atmospheric ’s Davis 68 Reines Cowan SPIRES:find title NEUTRINOS and date XX The Road Behind

  4. LHC                IceCube   J-PARC   

  5. Why Seesaws? Origin of -mass A natural theoretical way to understand why 3 -masses are very small. Type-I: SM + 3 right-handed Majorana ’s(Minkowski 77; Yanagida 79; Glashow 79; Gell-Mann, Ramond, Slanski 79; Mohapatra, Senjanovic 79) Type-II: SM + 1 Higgs triplet(Magg, Wetterich 80; Schechter, Valle 80; Lazarides et al 80; Mohapatra, Senjanovic 80; Gelmini, Roncadelli 80) Type-III: SM+ 3 triplet fermions (Foot, Lew, He, Joshi 89) Other variations or combinations (e.g., type-I +type-II in SO(10) GUT)

  6. Planck GUT to unify strong, weak & electromagnetic forces? Conventional (Type-one)SeesawPicture: close to the GUT scale Is the “seesaw scale” close to a fundamental physics scale? TeV SeesawIdea: driven by testability at LHC TeV to solve the unnatural gauge hierarchy problem? Naturalness? Testability? Fermi Why TeV Seesaws? Is the seesaw mechanism of -mass generation testable or not?

  7. ANSWER: to discover the Higgs boson(s) and to verify the Yukawa interactions What is the first step to test seesaws at the LHC?

  8.  LHC TeV     TeV Neutrino Physics ??? Why Not Try

  9. Part A Type-I Seesaw: add 3 right-handed Majorana neutrinos into the SM. or Diagonalization (flavor basis mass basis): Hence V is not unitary Seesaw: Strength of Unitarity Violation Type-I Seesaw

  10. Part A Natural case:no large cancellation in the leading seesaw term. 0.01 eV 100 GeV Unnatural case:large cancellation in the leading seesaw term. 0.01 eV 100 GeV TeV-scale (right-handed) Majorana neutrinos: small masses of light Majorana neutrinos come from sub-leading perturbations. Natural or Unnatural?

  11. Part A Given diagonal M_R with 3 eigenvalues M_1, M_2 and M_3, the leading (i.e., type-I seesaw) term of the light neutrino mass matrix vanishes, if and only if M_D has rank 1, and if (Buchmueller, Greub 91; Ingelman, Rathsman 93; Heusch, Minkowski 94; ……; Kersten, Smirnov 07). Tiny -masses can be generated from tiny corrections to this complete “structural cancellation”, by deforming M_D or M_R . Simple example: Structural Cancellation

  12. Part A L = 2like-sign dilepton events Fast Lessons • Lesson 1:two necessary conditions to test a seesaw model with heavy right-handed Majorana neutrinos at the LHC: • Masses of heavy Majorana neutrinos must be of O (1) TeV or below; • (B) Light-heavy neutrino mixing (i.e., M_D/M_R) must be large enough. Lesson 2:LHC-collider signatures of heavy Majorana ’s are essentially decoupled from masses and mixing parameters of light Majorana ’s. Lesson 3:non-unitarity of the light neutrino flavor mixing matrix might lead to observable effects in neutrino oscillations and rare processes. Lesson 4: nontrivial limits on heavy Majorana neutrinos can be derived at the LHC, if the SM backgrounds are small for a specific final state.

  13. Part A Lepton number violation: like-sign dilepton events at hadron colliders, such as Tevatron (~2 TeV) and LHC (~14 TeV). collider analogue to 0 decay dominant channel N can be produced on resonance Collider Signature

  14. Part A A single heavyN (minimal Type-II) Just for Illustration Han, Zhang (hep-ph/0604064, PRL): cross sections are generally smaller for larger masses of heavy Majorana neutrinos. Del Aguila et al (hep-ph/0606198): signal & background cross sections (in fb) as a function of the heavy Majorana neutrino mass (in GeV). Tevatron LHC

  15. Part A Potential: Naturalness? (t’ Hooft79, …, Giudice08) (1)M_is O(1) TeV or close to the scale of gauge symmetry breaking. (2) _ must be tiny, and _=0 enhances the symmetry of the model. L and B–L violation 0.01 eV Type-II Seesaw Type-II (Triplet) Seesaw: add 1 SU(2)_LHiggs triplet into the SM. or

  16. Part A From the viewpoint of direct tests, the triplet seesaw has an advantage: The SU(2)_L Higgs triplet contains a doubly-charged scalar that can be produced at colliders, depending only on its mass and independently of the Yukawa coupling. Signatures: Rough number of events for pair (N_4l) and single (N_2l) production of doubly-charged Higgs at the LHC (See, e.g., Han et al07; Akeroyd et al 08; Perez et al08; ……) Collider Signature

  17. Part A Incomplete cancellation between two leading terms of the light neutrino mass matrix in type-II seesaw scenarios. The residue of this incomplete cancellation generates the neutrino masses: tiny mass generation not small not small collider signature (Chao, Luo, Z.Z.X., Zhou 08) Discrete flavor symmetries may be used to arrange the textures of two mass terms, but fine-tuning seems unavoidable in the (Big – Big) case. Collider signatures: both heavy Majorana neutrinos and doubly-charged scalars are possible to be produced at the LHC (e.g., Azuleos et al06; del Aguila et al07; Han et al 07; ….). But decoupling between collider physics & the mechanism of neutrino mass generation is very possible. Type-(I+II) Seesaw

  18. Part A Possible LHC Signature

  19. Part A Type-II Possible combinations Type-I Type-III How to experimentally distinguish one type from another? Some Recent Works ★Han, Zhang, PRL (06) ★ Buckley, Murayama, PLB (06) ★ del Aguila et al, JPCS (06) ★ Bar-Shalon et al, PLB (06) ★ de Gouvea et al, PRD (07) ★ Atwood et al, PRD (07) ★ del Aguila et al, JHEP (07) ★ de Almeidaet al, PRD (07) ★ Chen, Mahanthappa, PRD (07) ★ Bajc et al, PRD (07) ★ Graesser, PRD (07) ★ Kersten, Smirnov, PRD (07) ★ Xing, PLB (08) ★ de Gouvea, Jenkins, PRD (08) ★ Chen et al, arXiv:0801.2011 ★ Bar-Shalon et al, arXiv:0803.2835 ★ Hirsch et al, arXiv:0804.4072 ★ del Aguila et al, arXiv:0806.0876 ★ Cogollo et al, arXiv:0806.3087 ★ Murayama, arXiv:0807.3775 ★ …… ★ Hektor et al, NPB (07) ★ Han et al, PRD (07) ★ Dorsner, Mocioiu, NPB (08) ★ Goravoa, Schwetz, JHEP (08) ★ Chao et al, PRD (08) ★ Akeroyd et al, PRD (08) ★ McDonald et al, JCAP (08) ★ Xing, PRD (08) ★ Ren, Xing, PLB (08) ★ Gogoladze et al, arXiv:0802.3257 ★Chao et al, arXiv:0804.1265 ★ Fileviez Perez et al, arXiv:0805.3536 ★ Hirsch et al, arXiv:0806.3361 ★ …… ★ Barr, Dorsner, PLB (06) ★ Bajc, Senjanovic, JHEP (07) ★ Fileviez Perez, PLB (07) ★ Dorsner, Fileviez Perez, JHEP (07) ★ Abada et al, JHEP (07) ★ Abada et al, arXiv:0803.0481 ★Franceschini et al, arXiv:0805.1613 ★ Gogoladze et al, arXiv:0805.2129 ★ Mohapatra et al, arXiv:0807.4524 ★ ……

  20. Part A Indistinguishable? Type-(I+II)

  21. Part A Non-unitary CP Violationis a straightforward consequence of TeV seesaws ---- it might manifest itself in both the oscillations of light neutrinos and the decays of heavy neutrinos. An uneasy feeling---- the generation of tiny neutrino masses seems always to be decoupled from appreciable collider signals of TeV Majorana neutrinos. Unnatural? Unnatural? Unnatural? Some Remarks Naturalness of the SM implies that there should exist a kind of new physics at the TeV scale. We wonder whether it is also responsible for the neutrino mass generation ---- TeV seesaws. It seems that people are struggling for a convincing reason to consider TeV seesaws ---- a balance between THnaturalness and EXtestability as the guiding principle?

  22. Part B The standard charged current interactions in the lepton flavor basis Correlated CC-interactions: Charged Current Interactions In the presence of heavy right-handed Majorana neutrinos, the overall 6×6 neutrino mass matrix can be diagonalized by a unitary matrix: either Type-I or Type-II seesaw. Neutrino flavor states in terms of light/heavy neutrino mass states:

  23. Part B A Language

  24. Part B R: production & detection of heavy Majorana neutrinos at LHC; V : oscillations & other phenomena of light Majorana neutrinos. They are two 3×3 sub-matrices of the 6×6 unitary matrix, hence they must be correlated with each other. This correlation characterizes the relationship between neutrino physics and collider physics. 2-dimensional rotation matrices in 6-dimensional complex space Correlation between V and R Strategy: parametrizing the 6×6 unitary matrix in terms of 15 rotation angles and 15 phase angles. The common parameters shared by R and V measure their correlation --- a general and useful approach.

  25. Part B Parametrization: V_0 is the standard form of the 3×3unitary neutrino mixing matrix: V = AV_0 Unitarity Violation Standard Parametrization

  26. Part B Exact Results of A and R They share 9 rotation angles & 9 phase angles: V—Rcorrelation.

  27. Part B In the SM, unitarity is the only constraint imposed on the CKM matrix. But the origin of neutrino masses must be beyond the SM. In this case,whether the MNS matrix is unitary or notrelies on the model or theory. In the scheme of Minimal Unitarity Violation, the 3×3neutrino mixing matrix V gets constrained as follows (Antusch et al 07): accuracy of a few percent! Effects of a few percent! 9 new mixing angles can maximally be ofO(0.1). Extra CP-violating phases exist in a non-unitary neutrino mixing matrix and might lead to observable effects (Fernandez-Martinez et al07). Experimental Bounds

  28. Part B All 9 rotation angles are expected to be small, but 9 phase angles may be large to generate new CP-violating effects. Approximations of A and R Observations: If the unitarity violation of V is close to the percent level, then elements of Rcan reach order of 0.1, leading to appreciable collider signatures for TeV-scale Majorana neutrinos. New CP-violating effects, induced by the non-unitarity of V, may show up in (short-baseline) neutrino oscillations. Such a parametrization turns out to be very useful in –phenomenology.

  29. Part B Example:V_0takes the tri-bimaximal mixing pattern which has Non-unitaryV takes the simple form CP violation (9 Jarlskog invariants): New CPV O(≤1%) UV-induced CP Violation

  30. Part B _ + Like the case of the non-standard interactions in initial & final states. Neutrino Oscillations Production and detection of a neutrino beam via CC weak interactions:

  31. Part B Jarlskog invariants of CP violation: Unitary: universal Jarlskog invariant = 2 area of each unitarity triangle. Non-unitary:9 different Jarlskog invariants, and trianglespolygons. “Zero-distance” (near-detector) effect at L = 0 : New Effects Oscillation probability in vacuum (e.g.,Antusch et al06, Z.Z.X. 08):

  32. Part B Short- or medium-baseline experiments in the neglect of matter effects (Fernandez-Martinez et al07). In particular (Z.Z.X. 08), ≈ 1 UV-induced CPV at 1% level? An Example A non-unitary deviation from the tri-bimaximal mixing pattern: Z.Z.X. 08, Luo 08 (matter effects), Z.Z.X., Zhou 08 (neutrino telescopes)

  33. Part B Neutrino Factory? Sensitivity ≤ 1% ? Numerical Illustration Example: an experiment with E  a few GeV&L ~ a few 100 km.

  34. Part B (Goswami, Ota 08; Luo 08) Genuine CPV Matter effect The same matter-effect term appears in _ _ oscillations (Luo 08). MSW Matter Effects Illustration: one heavy Majorana neutrinoand constant matter density.

  35. Part B In the mass basis Weak Interactions of N The standard weak interactions of 3 ’s with W, Z and H in the flavor basis: where

  36. Part B Xing, Zhou (in progress) Resonant enhancement with 4 heavy Majorana neutrinos. (Bray, Lee, Pilaftsis 07) ~ CP Violation CP violation: interference between tree and one-loop amplitudes of N.

  37. Part B New sources of CP violation are necessarily required. heavy Majorana ’s +CPV Why 3 known ’s have tiny masses seesaw leptogenesis Why we can exist in a matter world More on CP Violation The KM mechanism of CP violation is not the whole story to interpret the matter-antimatter asymmetry of our universe. Two reasons for this in the SM: ■CP violation from the KM mechanism is highly suppressed; ■ The electroweak phase transition is not strongly first order.

  38. Part B CP violation L-number asymmetry B-number asymmetry Leptogenesis Canonical idea(Fukugita, Yanagida 86): ●Lepton number violation at the tree level of Majorana neutrinodecays; ●Direct CP violation at the one-loop level of Majorana neutrino decays; ● At least 2 heavy Majorana neutrinos are required. Developments and variations(Davidson, Nardi, Nir, Phys. Rept. 08): ●Recent developments: spectator processes; finite temperature effects; flavor effects; N_2 leptogenesis; resonant (TeV) leptogenesis; …… ●Some variations: soft (SUSY) leptogenesis; type-II leptogenesis; Dirac leptogenesis; type-III leptogenesis; electromagnetic leptogenesis; …….

  39. Part B so something occurred over there one billion years ago we Cosmological matter-antimatter asymmetry are Seesaw + Leptogenesis Origin of -mass CP violation at colliders? L  B here today CP violation in neutrino oscillations A Grand Picture?

  40. Concluding Remarks Concluding Remarks The Road Ahead ★ We have known a lot about the properties of 3 known ’s, but we have not seen a convincing (quantitative and predictive) theory of -mass. Theory of ’s ★We need new theoretical guiding principles, so as to solve the uniqueness problem of model building. energy frontier cosmic frontier intensity frontier In his autobiographic bookThe Road Ahead,Bill Gates admits that “people often overestimate what will happen in the next two years and underestimate what will happen in ten”.  ★ We hope that the LHC will tell us much more behind 3 known ’s(new particles; symmetries; …….) Concluding Remarks Concluding Remarks

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