Probing left-right seesaw in colliders R. N. Mohapatra ACFI - PowerPoint PPT Presentation

Probing left-right seesaw in colliders R. N. Mohapatra ACFI Neutrino workshop, July 2017

Why left-right seesaw? n Two basic ingredients of seesaw: (i) Right handed neutrinos (ii) Broken B-L symmetry n Both automatic in left-right models n If scale is in the TeV range, a plethora of experimental implications

Left-Right model: n Gauge group : SU ( 2 ) SU ( 2 ) U ( 1 ) ⊗ ⊗ L R B L − n Fermions u P u ⎛ ⎞ P ⎛ ⎞ ν ⎛ ⎞ ν ⎛ ⎞ L R L ⎜ ⎟ R ⎜ ⎟ ⇔ ⎜ ⎟ ⎜ ⎟ ⇔ ⎜ ⎟ ⎜ ⎟ d ⎜ ⎟ d ⎜ ⎟ e e ⎝ ⎠ ⎝ ⎠ R ⎝ ⎠ L ⎝ ⎠ L R � � � � g µ µ L [ J W J W ] = ⋅ + ⋅ L L R µ µ 2 R n Parity a spontaneously M W R � M W L broken symmetry: ( Pati, Salam’74; Mohapatra, Pati’74;’74; Senjanovic, Mohapatra’75)

Left-Right seesaw: n Gauge group : SU ( 2 ) SU ( 2 ) U ( 1 ) ⊗ ⊗ L R B L (needed for − seesaw) n Fermions u P u ⎛ ⎞ P ⎛ ⎞ ν ⎛ ⎞ ν ⎛ ⎞ L R L ⎜ ⎟ R ⎜ ⎟ ⇔ ⎜ ⎟ ⎜ ⎟ ⇔ ⎜ ⎟ ⎜ ⎟ d ⎜ ⎟ d ⎜ ⎟ e e ⎝ ⎠ ⎝ ⎠ R ⎝ ⎠ L ⎝ ⎠ L R � � � � g µ µ L [ J W J W ] = ⋅ + ⋅ L L R µ µ 2 R n Parity a spontaneously M W R � M W L broken symmetry: ( Pati, Salam’74; Mohapatra, Pati’74;’74; Senjanovic, Mohapatra’75)

Breaking of LR and type I seesaw SU (2) L × SU (2) R × U (1) B − L ( Δ L=2) M N = fv R v R SU (2) L × U (1) Y ✓ ◆ h κ 0 M ν ,N = κ h κ fv R (Mohapatra, Senjanovic’79) U (1) em m ν ' � ( h κ ) 2 n Seesaw formula M N

Symmetry origin of Majorana Neutrinos n Electric charge formula: Q = I 3 L + I 3 R + B − L 2 n Above EW scale, ∆ Q = ∆ I 3 L = 0 → ∆ I 3 R = − 1 2 ∆ L

Parity breaking as origin of Majorana Neutrino mass n Electric charge formula in LR (contrast this with SM) Q = I 3 L + I 3 R + B − L 2 n Above EW scale, ∆ Q = ∆ I 3 L = 0 → ∆ I 3 R = − 1 2 ∆ L n Parity breaking à Majorana nu (RNM, Marshak’80)

Can type I seesaw scale be in the TeV range? n Typically, ; m D = h ν v wk n So for ; seesaw scale h ν ' 10 − 5 . 5 ⇠ h e v R could easily be in the TeV range and fit oscillation data; n Hence W R, Z’ accessible to colliders. M W R = g R v R ∼ fewTeV

Doublet breaking of LR and Inverse seesaw alternative n +singlets S SU (2) L × SU (2) R × U (1) B − L ( Δ L=0) M N = fv R < χ 0 R > v R ( ν S ) N SU (2) L × U (1) Y   h κ 0 0 h κ fv R 0   < φ 0 κ 1 > fv R µ 0 ( μ ~keV:weak Δ L=2) U (1) em m ν ' m D ( fv R ) − 1 µ ( fv R ) − 1 m T (RNM’86; RNM, Valle’86) D n Inverse seesaw more natural in LR; TeV scale.

Inverse seesaw and GUTs n Neutrino mass is determined by small mu- parameter à can be >> 10 -5.5 (could even h ν be ~h t allowing for quark lepton unification) (Dev, RNM’10) TeV Inverse seesaw embeddable in GUTs unlike TeV scale type I.

Rich phenomenology with TeV scale LR seesaw (type I) n Allows collider probes of seesaw ✔ n Large lepton flavor violation µ → e + γ , µ → e n Large lepton number violating processes ββ 0 ν

Collider signals for TeV scale LR type I seesaw n Vector boson signal: W R , Z’ (M~TeVs) n New fermion signal: N e,mu,tau (M~GeV-TeV) n Scalar boson signal: analog of SM Higgs

. n Vector Bosons:

Vector boson signal: How light can W R Be? n New interactions of quarks with W R affects low energy observables e.g. K L -K S, , B s -B s-bar, ✏ , ✏ 0 à M WR > 2.5 TeV (g R /g L ) (Zhang,An,Ji,RNM; Maiezza, Nemevsek,Nesti,Senjanovic;Blanke, Buras,Gemmler,Hiedsieck; Maiezza, Nemevsek) ✏ 0 / ✏ n Resolving puzzle à TeV W R (Cirigliano, Dekens, de Vries,Mereghetti’16)

Collider signals of LR seesaw (Type I) n Golden channel: (Two sources) W R → � i � k jj n W R mediates graph (Keung, Senjanovic’82) σ ( W R ) × BR ( Ne ) ∼ 14 . 8fb M WR = 3 TeV # ` ± ` ± = # ` ± ` ⌥ n Predicts A ` i ` j jj ∝ M N,ij and .

# ` ± ` ± 6 = # ` ± ` ⌥ What if ? n One resolution: General inverse seesaw   h κ 0 0 M N ∼ fv R h κ fv R 0 M N   fv R µ 0 n Neutrino mass is still tiny but collider signal diff. (Dev, RNM; Aniamati,Hirsch,Nardi) : n Second resolution: CPV in N-decay: (Gluza, Jelinski)

Current LHC searches n 0.1 M WR < M N < M WR ; n Leptons, jets clearly separated n Look for bumps in inv. Mass `` jj n for one lepton p T > 60 GeV n for the other p T > 40 GeV and also for jets (CMS)

Current limit from LHC n Current limit from dijet data: 2.8 TeV(g L =g R ) n LHC14 reach 5-6 TeV

g L = g R depends on scale of P breaking n In general if P-breaking takes place at a higher scale than SU(2) R breaking, g R < g L (Chang, RNM, Parida’84) n Important because this allows W R to be lighter than apparent collider and FCNC limits; n How low can g R be? Theoretical lower bound: g R > 0.66 g L (Brehmer, Hewett, Rizzo, Kopp,Tattersel’14; Dev, RNM, Zhang’16)

M N < 0.1 M WR n ATLAS/CMS sensitivities break down (Mitra, Ruiz, Scott, Spanowsky’16) n Use neutrino jets instead to recover lost sensitivity

Other contributions in LR n Golden channel: (second source) W R → � i � k jj n Heavy light mixing W L (RL) n mediated (Chen, Dev, RNM’13) q → W R → � + N ; q ¯ N → � W L n Measures M D

Limits on Z R Boson from LHC n . • W R –Z’ mass relation a test of LR (g L = g R ) s s 2cos 2 θ W cos 2 θ W Inverse M Z 2 = M W R Type I M Z 2 = M W R cos2 θ W cos2 θ W

SM or LR W → ` + N (A. Das talk) ` ± + W σ = σ 0 | V ` N | 2 v Like sign dileptons signal same as in LR case: r m ⌫ v But SM signal unobservable since V ` N ' M N v Current reach at LHC ~ 10 -3 ≤ 10 − 5

signal with enhanced ` ± ` ± jj in SM seesaw? V ` N n There have been attempts to build type I extensions of SM models where is much V ` N larger! n Conjecture: they will likely not increase the production rate in the mass range M W << M N, A `` jj ∝ m D M − 1 where and hence small N m D due to type I seesaw formula !! ` ± ` ± jj n If true, observation of could point to existence of W R (?).

Signal of minimal inverse seesaw (ISS)   h κ 0 0  M N ∼ fv R h κ 0 fv R  fv R µ 0 n Neutrino mass is still tiny but collider signal diff. trilepton and L-conserving. (Chen, Dev’11; Das and Okada’12)

. n New fermions: N 1,2,3

Theoretical upper limit on M N n Like the top quark in the SM, very large RHN mass will destabilize the vacuum. This gives an upper limit on: ∆ 0 R ∆ 0 R ∆ 0 † ∆ 0 † R R (RNM, PRD’86)

High mass range~0.1-1 TeV M N < M WR n Life time very short- Look for invariant mass of system ` jj N ν L, R + h

light N: possible displaced vertex searches at LHC n . (Helo, Hirsch, Dev, RNM, Zhang (@LHC)) n

SHIP Experiment- light N

. Scalars

New heavy neutral Higgs n LR is a two Higgs doublet model with the second Higgs coupling related to the SM Higgs by parity: n They have FCNH couplings which imply H 0 1 , A 0 ; M H 0 1 ,A 0 ≥ 10 TeV n Need higher energy colliders (HE-LHC, 100 TeV…) signature decay H 0 1 → b ¯ b

Seesaw related Higgs:Doubly charged scalars ∆ ++ n CMS n Neutral scalars : several

Neutral Seesaw Higgs n . H 0 3 ≡ Re ∆ 0 3 ' 1 � 1000GeV M H 0 R n Three domains of B-L breaking Higgs Δ 0 R masses (M H3 ) n M H3 ~ v R >> M h à à (Maiezza, Nemevsek, Nesti’15;Dev, RNM, Zhang’16) n M H3 << v R ~ M h n M H3 << M h << v R (~ few GeV to 100 MeV) (Dev, RNM, Zhang’17)

Rare decays of SM Higgs from seesaw n . h → `` 4 j • Displaced vertices at LHC (Maiezza, Nemevsek,Nesti’15; Miha’s talk; However, similar decay for SM seesaw: Lopez-Pavon et al’17)

Light H 3 (0.1-10 GeV) and displaced vertices n Motivation for light Higgs H 3 n H 3 analog of SM Higgs- connected to B-L breaking. n If SU(2) R x U(1) B-L is broken radiatively, there is a good chance that is light: H 0 3 ≡ Re ∆ 0 R (Dev, RNM, Yongchao Zhang, PRD’17; 1703.02471)

Reason for displaced vertices:FCNC constraints: n H 3 is a linear combination of SM Higgs h and LR new Higgs H 1 ( ) and has effective quark θ 1 , θ 2 coupling of the form: n For light H 3 , B and K-decays limit the value of mixing angles (barring cancellation)

FCNC Processes: n Expts: For B decays: n K-decays:

constraints on H 3 mixings from B-decays (Babar,Belle,LHCb) n Mixing with SM Higgs and heavy LR Higgs H 0 ( θ 1 , θ 2 ) are strongly constrained for m~GeV; (Dev, RNM, Zhang’16-17)