G. Senjanovi´ c LHC and the origin of neutrino mass Goran Senjanovi´ c ICTP B. Bajc, G. S., 06 B.Bajc, M. Nemevˇ sek, G. S., 07 In progress with A. Arhrib, B. Bajc, D. Ghosh, T. Han, G.-Y. Huang, I. Puljak, Neutrino 08-Christchurch 1
G. Senjanovi´ c With the degrees of freedom of the SM ν masses parametrized by Weinberg d = 5 effective operator L i HHL j L = Y ij M v 2 M Y = U P MNS m diag U T ν P MNS neutrino mass - Majorana M signals the appearence of new physics Neutrino 08-Christchurch 2
G. Senjanovi´ c Violation of lepton number: ∆ L = 2 • neutrino-less double beta decay ν 0 ββ a text-book fact • same sign charged lepton pairs in colliders Keung, G.S., 83 Neutrino 08-Christchurch 3
G. Senjanovi´ c • If M is huge, no hope of direct observation of new physics • M = 10 13 GeV − 10 14 GeV corresponds to Y of order one • However, small Yukawas are natural in a sense of being protected by symmetries. • Keep M free and look for theoretical predictions (grand unification) Neutrino 08-Christchurch 4
G. Senjanovi´ c Only 3 ways of producing the Weinberg operator By exchange of heavy • fermion singlet (1 C , 1 W , Y = 0) TYPE I SEESAW Minkowski, 77 Mohapatra, Senjanovi´ c, 79 Gell-Mann et al, 79 Glashow, 79 Yanagida, 79 • boson weak triplet (1 C , 3 W , Y = 2) TYPE II SEESAW Lazarides et al, 80 Mohapatra, Senjanovi´ c, 80 • fermion weak triplet (1 C , 3 W , Y = 0) TYPE III SEESAW Foot et al, 86 Neutrino 08-Christchurch 5
G. Senjanovi´ c I and II very well studied, III almost ignored in the past Neutrino 08-Christchurch 6
G. Senjanovi´ c Neutrino 08-Christchurch 7
G. Senjanovi´ c Neutrino 08-Christchurch 8
G. Senjanovi´ c All this by itself not more useful than just Weinberg operator unless • we can reach the scale M , interesting only for low M • we have a theory of these singlets, triplets (GUT for example) Neutrino 08-Christchurch 9
G. Senjanovi´ c This reminiscent of the Fermi theory of low energy weak interactions: saying that the four fermion interactions can be described by the exchange of a new particle (W boson) not useful except • when you can reach the new scale ( M W ) • you have a theory of this new particle: SU (2) L × U (1) Standard Model gauge theory that correlates different processes at low energies E << M W Neutrino 08-Christchurch 10
G. Senjanovi´ c ν mass window to new physics - if Majorana • Dirac case complete - new physics not necessary • SM with Majorana neutrino not complete • Majorana case connects m ν to different new phenomena like ν 0 ββ decay Neutrino 08-Christchurch 11
G. Senjanovi´ c Neutrino 08-Christchurch 12
G. Senjanovi´ c in general m ν not directly connected to ν 0 ββ decay: depends on the completion Example: LR symmetry with low W R , ν R masses has a nonzero ν 0 ββ decay even with y D , m ν → 0 Neutrino 08-Christchurch 13
G. Senjanovi´ c Neutrino 08-Christchurch 14
G. Senjanovi´ c This is why it is important for the see-saw to be traced in colliders: measure ∆ L = 2 operators not only in ν 0 ββ decays, but also in colliders Keung, Senjanovi´ c, 83 Neutrino 08-Christchurch 15
G. Senjanovi´ c L-R symmetric theories: SU (2 L ) × SU (2) R × U(1) gauge theory • ν L implies ν R • Type I seesaw: connects neutrino mass to scale of parity restoration • colliders: produce W R through Drell-Yan Neutrino 08-Christchurch 16
G. Senjanovi´ c Neutrino 08-Christchurch 17
G. Senjanovi´ c • direct test of parity restoration • direct test of lepton number violation • determination of W R and N masses Ferrari et al, 99 Gninenko et al, 07 LHC easily probes W R up to 3-4 TeV and ν R in 100 - 1000 GeV Neutrino 08-Christchurch 18
G. Senjanovi´ c L-R theory: also type II Type II: pair production of doubly charged Higgses, which decay into same sign lepton (anti lepton) pairs M ν = Y ∆ v ∆ probe directly M ν if no type I Kadastik, Raidal, Rebane,07 and references therein Neutrino 08-Christchurch 19
G. Senjanovi´ c Neutrino 08-Christchurch 20
G. Senjanovi´ c Datta, Guchait, Pilaftsis, 93 Datta, Guchait, Roy, 93 Ferrari et al, 99 Han, Zhang, 06 Gninenko et al, 07 del Aguila, Aguilar-Saveedra, Pittau, 07 del Aguila, Aguilar-Saveedra, 07 Han et al, 07 Akeroyd, Aoki, Sugiyama, 07 Fileviez Perez et al, 07 Kadastik, Raidal, Rebane,07 Neutrino 08-Christchurch 21
G. Senjanovi´ c Kersten and Smirnov, 07 Chao et al, 08 Franceschini, Hambye, Strumia, 08 Fileviez Perez et al, 08 many more in type I and also type II Neutrino 08-Christchurch 22
G. Senjanovi´ c Interesting theories: m Dirac ≪ M ν R (see-saw) M ν R , M W R ∼ O (1 − 10) TeV Neutrino 08-Christchurch 23
G. Senjanovi´ c Handle on a see-saw scale form grand unification : SO(10) theory • SO(10) unifies a family of fermions and postulates right-handed neutrinos • has L-R symmetry in a form of charge conjugation of Dirac • naturally both type I and II seesaw Neutrino 08-Christchurch 24
G. Senjanovi´ c • usually no low scale from running • typically Y Dirac ∼ Y top : fits with M R ∼ 10 14 GeV Such theories have a natural see-saw mechanism ( m ν and ν 0 ββ well described) but no low see-saw scale (no ∆ L = 2 in colliders) Neutrino 08-Christchurch 25
G. Senjanovi´ c Take for example the SO(10) model with Yukawas � � Y ij 10 10 H + Y ij 16 j L Y = 16 i 126 126 H F F Lazarides, Shafi, Wetterich, 81 Babu, Mohapatra, 92 Bajc, Senjanovi´ c, Vissani, 02 Only two 3 × 3 symmetricYukawa matrices Y 10 and Y 126 to describe all light fermions ( m d , m u , m e , m ν ) Neutrino 08-Christchurch 26
G. Senjanovi´ c Full theory with such Yukawas for example in the minimal renormalizable supersymmetric SO(10): • three copies of 16 F • 210 H , 126 H , 126 H , 10 H Clark, Kuo, Nakagawa, 83 Aulakh, Mohapatra, 83 Aulakh, Bajc, Melfo, Senjanovi´ c, Vissani, 04 The theory over constrained and quite predictive Neutrino 08-Christchurch 27
G. Senjanovi´ c Some evidence that constraints from Higgs sector and Yukawa sector are in contradiction Aulakh, 05, 06 Bajc, Melfo, Senjanovi´ c, Vissani, 05 Bertolini, Malinsky, Schwetz, 06 Although some new hope for consistent fit comes from recent (yet unpublished) results Dorˇ sner, Nemevˇ sek, to appear possibility: relate proton decay branching ratios to neutrino masses and mixings. Neutrino 08-Christchurch 28
G. Senjanovi´ c Even with new physics - only indirect Simple predictive GUT candidate with measurable seesaw? Neutrino 08-Christchurch 29
G. Senjanovi´ c MINIMAL SU(5) The minimal Georgi-Glashow model ruled out because Minimal: 24 H + 5 H + 3(10 F + 5 F ) 1. gauge couplings do not unify - 2 and 3 meet at 10 16 GeV (as in susy), - but 1 meets 2 too early at ≈ 10 13 GeV 2. neutrinos massless (as in the SM) Neutrino 08-Christchurch 30
G. Senjanovi´ c Add just one extra fermionic 24 F New Yukawa terms (higher dimensional operators a must as in the minimal model) F 24 F 5 H + 1 L Y ν = y i 0 ¯ 5 i 5 i ¯ y i � � 1 24 F 24 H + ... 5 H + h.c. F Λ Under SU(3) C × SU(2) W × U(1) Y decomposition 24 F = (1 , 1) 0 + (1 , 3) 0 + (8 , 1) 0 + (3 , 2) 5 / 6 + (¯ 3 , 2) − 5 / 6 Neutrino 08-Christchurch 31
G. Senjanovi´ c singlet S = (1 , 1) 0 triplet T = (1 , 3) 0 y i T T + y i � � L Y ν = L i S S H + h.c. Mixed Type I and Type III seesaw: � � T y j S y j y i + y i ( M ν ) ij = v 2 T S m T m S → one massless neutrino Neutrino 08-Christchurch 32
G. Senjanovi´ c The only possible pattern: m 3 ≪ m 8 ≪ m (3 , 2) ≪ M GUT A solution m 3 = 10 2 GeV m 8 = 10 7 GeV m (3 , 2) = 10 14 GeV M GUT = 10 16 GeV Neutrino 08-Christchurch 33
G. Senjanovi´ c 1-loop result: > 10 15 . 5 GeV (p decay) For M GUT ∼ < 1TeV → m 3 ∼ Prediction of the model Neutrino 08-Christchurch 34
G. Senjanovi´ c m max − M GUT at two loops 3 � m max � log 10 3 GeV 3.75 3.5 3.25 3 2.75 2.5 2.25 � � M GUT log 10 15.6 15.7 15.8 15.9 16 GeV Neutrino 08-Christchurch 35
G. Senjanovi´ c T at LHC ? T 0 , ± weak triplet → produced through gauge interactions (Drell-Yan) pp → W ± + X → T ± T 0 + X pp → ( Z or γ ) + X → T + T − + X Neutrino 08-Christchurch 36
G. Senjanovi´ c Neutrino 08-Christchurch 37
G. Senjanovi´ c pp -> T +- T 0 + X at LHC 10 1 10 0 T + T 0 T - T 0 cross section (pb) 10 -1 10 -2 10 -3 10 -4 100 200 300 400 500 600 700 800 900 1000 m T (GeV) Neutrino 08-Christchurch 38
G. Senjanovi´ c Γ T ≈ m T | y T | 2 The best channel is like-sign dileptons + jets T | 2 | y j 20 × | y i T | 2 j + 4 jets) ≈ 1 BR ( T ± T 0 → l ± i l ± k | y k T | 2 ) 2 ( � Neutrino 08-Christchurch 39
G. Senjanovi´ c Same couplings y i T contribute to • ν mass matrix and • T decays Neutrino 08-Christchurch 40
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