University College London. Frank Deppisch. University College London

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1 Frank Deppisch University College London 17 th Lomonosov Conference Moscow 20-26/08/2015

2 Two possibilities to define fermion mass ν R ν L ν L = ν L ν R ν R = ν R ν L Dirac mass analogous to other fermions but with m ν ΛEW couplings to iggs Majorana mass, using only a left-handed neutrino Lepton Number Violation Y ν ν L ν R ν L Y ν ν L ν L 2 / 18 Frank Deppisch Neutrinos and Collider Physics 26/08/2015

3 Effective operator for Majorana neutrino mass Only dimension-5 operator beyond SM L 1 2 h ij Λ LNV L i c T L j 1 2 m ν ij ν c i ν j L L Seesaw Mechanisms Three possible mediators at tree level Seesaw I Seesaw II Seesaw III Singlet L L Y ν Y ν Triplet Triplet L L Y ν Y ν L Y 3 L 3 / 18 Frank Deppisch Neutrinos and Collider Physics 26/08/2015

4 Effective operator for Majorana neutrino mass Only dimension-5 operator beyond SM L 1 2 h ij Λ LNV L i c T L j Radiative Generation via Loops Alternative to Seesaw, e.g. R-Parity Violating SUSY 1 2 m ν ij ν c i ν j L L d L d R L λ λ L d R d L 4 / 18 Frank Deppisch Neutrinos and Collider Physics 26/08/2015

5 Seesaw I mechanism with TeV scale heavy neutrinos Standard Seesaw with small Yukawa couplings Y ν 10 6 M N /TeV Bent Seesaw I mechanisms (e.g. Inverse Seesaw) Decouple Λ LNV from heavy neutrino mass Example Y ν = 10 2 GeV M = 10 3 GeV M = 0 Y ν 0 Y ν μ M 0 M μ Large Yukawa couplings 10 2 Quasi-Dirac heavy neutrino Quasi-Dirac Majorana Neutrino m ν = 0.1 ev 5 / 18 Frank Deppisch Neutrinos and Collider Physics 26/08/2015

6 Seesaw I mechanism with TeV scale heavy neutrinos Standard Seesaw with small Yukawa couplings Bent Seesaw I mechanisms (e.g. Inverse Seesaw) Decouple Λ LNV from heavy neutrino mass Example Y ν 10 6 M N /TeV M = 0 Y ν 0 Y ν μ M 0 M μ LNV in resonant N production suppressed by Δm N Γ N μ Γ N FFD, Dev, Pilaftsis NJP 17 (2015) 7, / 18 Frank Deppisch Neutrinos and Collider Physics 26/08/2015

7 Constraints on coupling to leptons V ln Neutrinoless Double Beta Decay GERDA stringent for pure Majorana N Peak Searches in Meson Decays π, K eν Belle Beam Dump Experiments e.g. PS191, CARM LBNE LNV Meson Decays K eeπ SiP Z Decays LEP: L3, Delphi FCC-ee FFD, Dev, Pilaftsis NJP 17 (2015) 7, Electroweak Precision Tests EWPD: Fit of electroweak precision observables, lepton universality observables 7 / 18 Frank Deppisch Neutrinos and Collider Physics 26/08/2015

8 Constraints on coupling to leptons V ln LEP2, ILC e + e Nν, N ew, νz, ν LC (ATLAS, CMS, LC14) Drell-Yan Production Izaguirre, Shuve PRD 91 (2015) 9, Majorana N Same-sign dilepton signal (Quasi-)Dirac N Trilepton signal Modified searches for lighter neutrinos Long-lived neutrinos FFD, Dev, Pilaftsis NJP 17 (2015) 7, / 18 Frank Deppisch Neutrinos and Collider Physics 26/08/2015

9 Production at LC via Z portal Ability to measure small couplings via displaced vertices Charged LFV through heavy portal N can only decay through heavy-light suppressed coupling θ = Y ν /m N FFD, Desai, Valle PRD 89, / 18 Frank Deppisch Neutrinos and Collider Physics 26/08/2015

10 Extension of the Standard Model SU 3 SU(2) L SU(2) R U(1) B L Production of heavy neutrinos with gauge coupling strengths via right-handed charged current (Keung, Senjanovic 83) Complementarity to 0ννβ and charged LFV Das, FFD, Kittel, Valle PRD 86 (2012) / 18 Frank Deppisch Neutrinos and Collider Physics 26/08/2015

11 Extension of the Standard Model SU 3 SU(2) L SU(2) R U(1) B L Production of heavy neutrinos with gauge coupling strengths via right-handed charged current (Keung, Senjanovic 83) Complementarity to 0ννβ and charged LFV 2.8s hint for excess at CMS Not compatible with minimal LR symmetry g R = g L Only one 1 out of 14 potential signal events is LNV Only ee, no mm 2 2 No clear discrete excess in m lqq = m N No excess at ATLAS Search only for SS leptons FFD, Gonzalo, Patra, Sahu, Sarkar, PRD 90 (2014) 5, (using CMS data) 11 / 18 Frank Deppisch Neutrinos and Collider Physics 26/08/2015

12 Excesses in other resonant searches around 2 TeV WW, ZZ or WZ up to ATLAS (hadronic) no excess in semi-leptonic ch. lnj W CMS (leptonic) tension with hadronic ch. jj small ATLAS and CMS (1.5s,1.9s) tension with tb channel Brehmer, ewett, Kopp, Rizzo, Tattersall, arxiv: / 18 Frank Deppisch Neutrinos and Collider Physics 26/08/2015

13 Combined interpretation in effective LR model σ pp W R Br W R WZ σ pp W R Br W R W σ pp W R Br W R jj σ pp W R Br W R Ne Br N ejj = 0.66 ± 0.4 fb Model parameters M WR = 1.9 TeV M N = 1.6 TeV g R g L : Ratio of SU(2) R/L gauge couplings sin θ W : W W R mixing angle sin θ N = 0: ν N mixing angle FFD, Graf et al arxiv: / 18 Frank Deppisch Neutrinos and Collider Physics 26/08/2015

14 Combined interpretation in effective LR model σ pp W R Br W R WZ σ pp W R Br W R W σ pp W R Br W R jj σ pp W R Br W R Ne Br N ejj = 0.66 ± 0.4 fb Model parameters M WR = 1.9 TeV M N : eavy neutrino mass g R g L = 0.57 sin θ W = sin θ N = 0: ν N mixing angle FFD, Graf et al arxiv: / 18 Frank Deppisch Neutrinos and Collider Physics 26/08/2015

15 Classic Scenario Generation via heavy neutrino decays Competition with LNV washout processes Conversion to baryon asymmetry EW sphaleron processes at T 100 GeV Observed asymmetry η B n B n B n γ = (6.20 ± 0.15) What if we observe lepton number violating processes at the LC or in 0ννβ? 15 / 18 Frank Deppisch Neutrinos and Collider Physics 26/08/2015

16 Compare LC cross section with lepton number asymmetry washout Γ W > M PM X 3 T 4 K 1 (M X /T) f q1 q 2 (M X / s) (s σ LC ) Lower limit on total washout rate Observation of LC corresponds to highly effective washout Γ W / 1 Excludes baryogenesis models that generate asymmetry above M X FFD, arz, irsch PRL 112 (2014) / 18 Frank Deppisch Neutrinos and Collider Physics 26/08/2015

17 LNV effective operators are of mass dimensions 5, 7, 9, 11, 0νββ sensitive to operators at scales FFD, arz, irsch, uang, Päs PRD 92 (2015) νββ T 1/ yr m ν 0.1 ev Λ GeV 0νββ T 1/ yr Λ 9 1 TeV LC can deep-probe anatomy of LNV operators at TeV scale Observation of LNV and LFV would give information at what temperatures operators are in equilibrium can provide strong constraint on baryogenesis models and falsify highscale scenarios 17 / 18 Frank Deppisch Neutrinos and Collider Physics 26/08/2015

18 Neutrinos much lighter than other fermions Dirac or Majorana? Lepton Number Violation? Mechanism of neutrino mass generation? At what scale? Neutrino physics is BSM physics Seesaw I Sterile neutrinos Seesaw II Scalar triplet pp W ++ W, ++ l + l +, m ++ > 500 GeV Seesaw III Fermion triplet pp W Σ + Σ 0, m Σ > 250 GeV Extended gauge sectors Supersymmetry SUSY Seesaw / R-Parity violating SUSY (loop-mediated neutrino masses) LC probes neutrino mass models at TeV scale Strong synergy with 0νββ LC can deep-probe anatomy of 0νββ LNV operators Lepton Number Violation as smoking gun Can falsify high-scale baryogenesis BUT: LNV not necessarily predicted 18 / 18 Frank Deppisch Neutrinos and Collider Physics 26/08/2015