Probing the Majorana nature in radiative seesaw models at collider experiments Shinya KANEMURA (U. of Toyama) M. Aoki, SK and O. Seto, PRL 102, 051805 (2009). M. Aoki, SK and O. Seto, PRD80, 033007 (2009). M. Aoki, SK, K. Tsumura, K. Yagyu, PRD80, 015017(2009). M. Aoki and SK, arxiv: 1001.0092. LCWS2010, Beijing, China, March 26-30. 2010
Introduction Higgs sector remains unknown Minimal/Non-minimal Higgs sector? Higgs Search is the most important issue to complete the SM particle contents. We already know BSM phenomena: Neutrino oscillation Dm 2 ~ 8 10-5 ev 2, Dm 2 ~ 3 10-3 ev 2 Dark Matter W DM h 2 ~ 0.11 Baryon Asymmetry of the Universe n B /s ~ 9 10-11 To understand these phenomena, we need to go beyond-sm
Neutrino Mass Neutirno Mass Term (= effective Dim-5 Operator) L eff = (c ij /M) n i Ln j L f f Mechanism for tiny masses: m n ij= [c ij (v/m) ] v < 0.1 ev <f> = v = 246GeV Seesaw (tree level) m n ij = y i y j v 2 /M M ~ 10 14 GeV (for y i =O(1)) Quantum Effects (Radiative Seesaw) m n ij = [1/(16p 2 )] N C ij v 2 /M M=O(1) TeV N-th order of perturbation
Neutrino Mass Neutirno Mass Term (= effective Dim-5 Operator) L eff = (c ij /M) n i Ln j L f f Mechanism for tiny masses: m n ij= [c ij (v/m) ] v < 0.1 ev <f> = v = 246GeV Seesaw (tree level) m n ij = y i y j v 2 /M M ~ 10 14 GeV (for y i =O(1)) Quantum Effects (Radiative Seesaw) m n ij = [1/(16p 2 )] N C ij v 2 /M M=O(1) TeV N-th order of perturbation
Radiative Seesaw Model A Neutrino Mass Generation Mechanism at Loop Feature 1. Extended Higgs (scalar) sector 2. Majorana nature Zee Model 2HDM + (charged singlet w + ) Lepton # violaiting interaction m Merit A super high scale is not necessary. Tiny m n can naturally be deduced from TeV scale physics by higher order perturbation Physics at TeV: Testable at collider experiments Excluded by the data
Models of radiative nnff generation Tiny n-masses come from loop effects Ma (1-loop) Ma Zee-Babu (2-loop) Babu, PLB203,132(1988) Babu Aoki-Kanemura-Seto (3-loop) PRL102, 051805(2009) m n ij = [1/(16p 2 )] N C ij v 2 /M M=O(1) TeV AKS Common features Extended Higgs sector Source of the Majorana nature
The Zee-Babu model Model: SM + w +, k ++ (charged scalar singlets: L#=2) Babu, PLB203,132(1988) Source of the Majorana nature: LNV interaction (m) Neutrino masses generated at 2-loop f em ~ f et ~ f mt /2 (Normal Hierarchy) g mm : g mt : g tt ~ 1 : m m /m t : (m m /m t ) 2 Constraints on couplings from LFV data Bound on the masses: m w > 160 GeV, m k > 770 GeV (for g mm ~ 1 ) Babu, Macesanu (2003), Aristizabal Sierra, Hirsch (2006)
The Ma model (even) φ Source of the Majorana nature: TeV-scale RH neutrino n No tree-level neutrino Yukawa: Exact Z 2 -parity L (even) Model: 2HDM (Z 2 -even Φ 1, Z 2 -odd Φ 2 ) + RH-Neutrino (Z 2 -odd N R ) Neutrino masses generated at 1-loop The lightest Z 2 odd particle can be DM N R (odd) l 5 DM (odd) DM candidate: Either Φ 0 2 (x 0 r, x 0 i) or N R A special 2HDM: Φ 2 =(x +, x 0 r +i x 0 i) does not receive VEV The second doublet is so-called Inert Doublet, or Dark Doublet Example of parameters that explain the neutrino data, LFV data and the WMAP: M Na =3 TeV, M xr =50 GeV, M xi =60GeV, M x+ =100GeV l 5 =O(10-2 ) h ia =O(10-5 )
Φ2 Φ1 The 3-loop model (AKS) Source of the Majorana nature: TeV-scale RH neutrino Exact Z 2 -parity : No tree-level neutrino Yukawa Model: Type-X 2HDM (Z 2 -even Φ 1, Φ 2 ) + singlet scalars (Z 2 -odd h, S-) + RH-Neutrino (Z 2 -odd N R ) M.Aoki, SK, O.Seto, PRL 102,051805(2009) n L (even) φ (even) N R (odd) 1. Neutrino masses are generated at 3-loop. 2. DM: the lightest Z 2 odd particle. DM candidate: Either h or N R 3. Electroweak Baryogenesis 1 st order phase transition Extra CP Phases In addition, 3-loop generation may be more natural to explain tiny neutrino masses by the TeV-scale dynamics. [ with Coupling = O(1 )] h e 1,2 = k = O(1) >> h m 1,2 >> h t 1,2 for M NRa = 3TeV, DM (odd)
Typical mass spectra in RSMs The 2-loop model (Zee-Babu) The 1-loop model (Ma) The 3-loop model (Aoki-Kanemura-Seto) w + k ++ N R N R h SM h A SM x+ h H H + SM S + x 0 i x 0 r(dm) h(dm) L=2 Normal Z 2 -odd
Test of the models at collider experiments Common features of the radiative seesaw models Extended Higgs sector Charged Higgs physics (all) Physics of k ++ (Zee-Babu model) Scalar DM (Ma, AKS) invisible decay of the SM-like Higgs The Majorana nature LNV couplings (Zee-Babu) or TeV-scale N R with Z 2 parity (Ma, AKS) LHC: pp (7 TeV 1fb -1, 14 TeV 10-100fb -1 ) Structure of Higgs sector, Invisible decay of Higgs can be explored ILC: e + e -, e - e - (E=300GeV-1TeV, 100fb -1-1ab -1 ) Not only the Higgs sector and DM, but also Majorana nature can be explored
Physics of Extra Higgs at LHC Ma model Signal: ll + E T x 0 ix 0 * x r 0 rx 0 r x 0 rx 0 r m x0 =150GeV Pair production of the second doublet scalars ---- AH + (x 0 ix + r) ---- AH - (x 0 ix - r) ----AH (x 0 ix 0 r) 3-loop (AKS) model Aoki, SK, Tsumura, Yagyu (2009) (Type-X Yukawa) For the singlet S +, challenging @ LHC pp S + S - H + H - hh (0.37fb) pp H + H - (54fb) m S =400GeV, m H+ =150GeV Pair production of the singlet S + S -
Physics of Extra Higgs at LHC Zee-Babu model Singly charged Higgs Doubly charged scalars can be discovered at LHC if it is lighter than 800 GeV Discrimination from triplet models? Triplet: (H ++, H +, H 0 ) W + H + H coupling is a useful probe Derivative gauge coupling in the triplet model No-such coupling in Zee-Babu model w + w - production Triplet models k ++ k -- production
ILC
TeV Right handed neutrinos at ILC Radiative Seesaw Z 2 -odd RH neutrinos Differently from tree level seesaw scenario, h ea coupling can be even O(1) in RSMs The t-channel NR mediation diagram can be significant 1-loop model (Ma) h e a < 10-2 s-channel dominannt e+e- x + x - 3-loop model (AKS) h e a = O(1) t-channel dominannt e+e- S + S -
Ma model M Na =3 TeV, M xr =50 GeV, M xi =60GeV, M x+ =100GeV l 5 =O(10-2 ) h ia =O(10-5 ) (x 0 r: DM) l 5 s(e+e- x + x - ) = 92 (10) fb (m H+ =100 (150) GeV for E=500GeV) e+e- x + x - W + W -(*) x 0 rx 0 r jjjj x 0 rx 0 r (jjmn x 0 rx 0 r ) m x+ =100GeV Signal: jj m+ E Main BG: WW * ZZ, gg, Zg with a m missing m x+ =150GeV Signal: 4 jjjj + E Main BG: WW nn, tt x - x + Aoki, SK, arxiv:1001.0092 x + x -
3-loop Model (AKS) h e 1,2 = k = O(1) >> h m 1,2 >> h t 1,2 for M NRa = 3TeV, m H+ =100 GeV, m h =50GeV t-channel effect dominant s(e+e- S + S - ) = 87 fb (m S+ =400 GeV for E=1TeV) S + S + e+e- S + S - H + H - t + t - B(S + H + h) = 100 % B(H + t + h) ~ 100 % hh nn hh Signal: t + t - + E Main BG t + t -, t + t - nn, H + H - S - Aoki, SK, arxiv:1001.0092 S -
Direct Test of Majorana Nature at e - e - collisions at ILC Tree Seesaw 1-loop Seesaw E. Ma h ia h ja (v/m N ) = O(10-12 ) O(10-4 ) 2-loop Seesaw Zee-Babu 3-loop Seesaw Krauss, Nasri, Trodden (2002) Aoki, SK, Seto (2009) O(10-1 ) O(1)
Test the Majorana Nature at ILC The sub-diagram itself can be directly measured at the e - e - collision. Aoki, SK, arxiv:1001.0092 h ea =O(1) Signal: t - t - + E (AKS); m - m - + E (Zee-Babu) There is no substantial BG, the signals can be easily seen
Summary Radiative seesaw models are interesting, where the scale of neutrino mass generation can be lowered to TeV scales. We discussed collider phenomenology in these models They are characterized by Extended Higgs sector The Majorana nature (LNV interaction, TeV RH neutrinos) At the LHC, the Higgs sectors can be tested at LHC. The Majorana nature can also be directly tested at the ILC. The combined study at LHC and ILC (e + e -, e - e - ) can clarify the possibility of radiative seesaw scenarios.
Backup
Physics of h (DM) Invisible Decay of h h is the SM-like Higgs but can decay into hh. B(h hh) = 36 (34) % for m h =48 (55) GeV Testable via the invisible Higgs decay at LHC Direct Search h from the halo can basically be detected at the direct DM search (CDMS, XMASS) h Nucleus (Xe, Ge) h Observing the release energy
Extended Higgs sector in RSMs Higgs Invisible decay Ma h SM x 0 r x 0 r AKS h SM hh Extra Neutral Higgs bosons Ma x 0 i Z* x 0 r (Inert doublet) AKS H 0 t t (Type-X 2HDM) [MSSM H 0 bb (Type-II 2HDM)] Singly charged Higgs bosons Zee-Babu w + mn, t n (> e n ) Ma x + l + n x 0 r (Inert doublet) AKS H + t n (Type-X 2HDM) S + H + h t n h [MSSM H + t b, t n (Type-II 2HDM)] Doublely charged Higgs boson Zee-Babu k -- m - m -
Seesaw Mechanism? Super heavy RH neutrinos (M NR ~ 10 10-15 GeV) Hierarchy between M NR and m D generates that between m D and tiny m n (m D ~ 100 GeV) nnff m n = m D2 /M NR Minkowski Yanagida Gell-Mann et al L Simple, compatible with GUT etc Introduction of a super high scale Hierarchy for hierarchy! Far from experimental reach R
The Higgs sector The Higgs sector Φ 1, Φ 2 (2HDM) + S +, η (singlets) To avoid FCNC, additional softlybroken Z 2 symmetry is introduced : MSSM Type Y Our model Type X Φ 1 + Φ 1, Φ 2 - Φ 2 by which each quark/lepton couples to only one of the Higgs doublets. 4 types of Yukawa interactions! Neutrino data prefer a light H + (< 200GeV) Choose Type-X Yukawa to avoid the constraint from b sγ. F 1 only couples to Leptons F 2 only couples to Quarks NLO, Ciuchini et al 98,. NNLO by Misial et al. 2006 Becher, Neubert 2006 Aoki, SK, Tsumura, Yagyu, arxiv:0902.4665[hep-ph]
Lagrangian Z 2 even(2hdm) + Z 2 odd(s +, h 0, N Ra ) Z 2 (exact) : to forbid tree n-yukawa and to stabilize DM ~ Z 2 (softly-broken): to avoid FCNC Z 2 even 2HDM Z 2 odd scalars Interaction RH neutrinos
Strong 1 st Order Phase Transition Effective Potential at high T Sphaleron decoupling m h =120GeV m H +=m H =100GeV M=100 GeV, m S =200GeV f C /T C > 1 Region of strong 1 st OPT SM In SM, m h is too smaller than LEP bound f C /T C < 1 Our Model The condition can be satisfied with m h > 114 GeV, when A and/or S + have 2 non-decoupling property. This region is compatible with neutrino data and DM abundance.