Probing TeV Scale Origin of Neutrino Mass and Baryon Excess R. N. Mohapatra. INFO2015, Santa Fe

Transcription

1 Probing TeV Scale Origin of Neutrino Mass and Baryon Excess R. N. Mohapatra INFO2015, Santa Fe

2 Neutrino mass and BSM physics n Neutrino are now known to have mass! n Since m ν =0 in SM, neutrino mass is first evidence of physics beyond SM (BSM). n Origin of matter cannot be understood within SM: its understanding requires BSM physics. n This talk: Could both these problems be connected to physics at TeV scale and be accessible at colliders and in low energy searches?

3 Weinberg Effective operator as starting paradigm for m ν n Add effective operator to SM: λ LHLH M n After symmetry breaking m ν = λ v2 wk M n M is BSM physics and is arbitrary; can be large à M v wk small m ν n Operator breaks lepton number!!

4 Scale of L-violation n Naive lore: n Neutrino osc dataà n So if λ 1; M m ν = λ v2 wk M m ν GeV << ev (Beyond reach!) n Dimensional analysis arguments, however, can be quite misleading!! n To explore true scale, UV completion of Weinberg operator essential (build models)!!

5 Seesaw as step towards UV completion of Weinberg Op. n Add right handed nu N and a Majorana mass for it: Seesaw mechanism: m ν h 2 ν v M wk R 2 Minkowski 77, Gell-Mann, Ramond, Slansky;Yanagida; Glashow; Mohapatra,Senjanovic 79 n Majorana mass of N à L violation n Could Majorana N be accessible (~TeV)?

6 Bonus from Seesaw UV completion Leptogenesis origin of matter n Fukugita and Yanagida (1986) RH neutrino is its own anti-particle: so it can decay to both leptons and anti-leptons: n Proposal: R = ( 1+ ε ) R = ( 1 ε) n Generates lepton asymmetry: L (Leptogenesis) n Sphalerons convert leptons to baryons (Kuzmin, Rubakov,Schaposnikov 83) n Related to neutrino mass and hence attractive; motivates search for CP violation in nu-oscillations!!

7 Can seesaw and hence leptogenesis scale be TeV s? n Search for explicit UV complete models n Guiding principle in this search (i) Existence of N should be predicted by theory (ii) Seesaw scale should be related to symmetry n Two simple theories that conform to these: (i) Left-right model where N is the parity partner of ν L and seesaw scale is SU(2) R scale could be TeV (ii) SO(10) GUT where N+15 SM fermions =16 spinor

8 Naturalness arguments for lower Seesaw scale n Correction to Higgs mass from RHN Yukawa 1 TeV 2 à M R < 7 x 10 7 GeV (not a GUT scale) (Vissani 97; Clarke, Foot, Volkas 15) n Explore TeV scale models!!

9 SUSY+Leptogenesis also prefer low scale seesaw n For leptogenesis to occur, M N < T reheat ; n Gravitino overclosing prefers that T reheat < 10 6 GeV (Kohri et al.) à Hence preference of leptogenesis for lower seesaw scale!!

10 This talk: TeV LR seesaw n A natural TeV scale theory for neutrinos n n Minimal SUSY LR requires TeV scale L-violation How to probe this TeV scale theory in colliders n Leptogenesis with TeV scale L and constraints

11 Left-Right Model Basics n LR basics: Gauge group: n Fermions n Parity a spontaneously broken symmetry: (Mohapatra, Pati, Senjanovic 74-75) L B R L U SU SU ) (1 (2) (2) L L d u R R d u L L e ν R R e ν P P ] [ 2 R R L L W J W J g L µ µ µ µ + = M WR M WL

12 Why these models are attractive? n New way to understanding parity violation: n A more physical electric charge formula n Explains small neutrino masses via seesaw: n Solves strong CP problem: n With supersymmetry, provides a naturally stable dark matter (automatic R-parity) n Can explain the origin of matter (see later)

13 New Higgs fields and Yukawa couplings n LR bidoublet: n Triplet to break B-L and generate seesaw: = φ φ φ φ φ Δ Δ Δ Δ Δ = L Y = h LφR + h L φr + frr R + h.c. < Δ >= R v = ' 0 0 κ κ φ R

14 Seesaw scale is SU(2) R breaking Scale SU(2) L SU(2) R U(1) B L v R SU(2) L U(1) Y (ΔL=2) κ M ν,n = U(1) em M N = fv R Seesaw n If v R ~ TeV, L-violaion is TeV scale n Any theoretical justification for TeV v R? 0 hκ hκ fv R m ν (hκ)2 M N

15 Minimal SUSY left-right requires low scale W R n Supersymmetrize this minimal LR model n First consequence: Tree level global minimum violates electric charge: < ++ >= 0 (i) unless R-parity is broken (Kuchimanchi, R. N. M. 94, 95) (ii) W R mass has an upper limit: M WR M SUSY f i.e. W R is in TeV range! However due to RPV, neutrino masses get complicated!

16 Minimal SUSYLR with exact R-parity n Extend with a singlet and add one loopà RP exact! ( Babu, R. N. M. 08; Babu, Patra 14; Basso, Fuks, Krauss, Porod 15) n Upper bound on W R required to conserve electric charge; n Implies a light (< TeV) doubly charged Higgs n Neutrino masses from usual seesaw

17 Seesaw formula in TeV scale LR models n Generic LR models with parity down to TeV, à Seesaw formula < 0 R >v R < 0 L > κ2 m ν f κ2 v R m T D n First term too large for TeV seesaw; two ways to prevent v R 1 m D fv R (i) decouple P breaking from SU(2) R (ii) SUSYLRà zero at tree level; 1-loop small L h τ h τ φ φ v L h2 τ f 2 κ 2 M SSB 16π 2 v 2 R R

18 Small Neutrino masses with TeV WR (non-susy) n. L Y = h LφR + h L φr + h.c. n Using φ = n How to get small (i) κ 0 0 κ' à (ii) Cancellation with M = hκ + hκ m D = hκ + hκ m ν κ = 0; h for TeV seesaw: ( h SM κ, κ similar (iii) assume texture for Dirac mass e ) h, h much larger

19 Right handed neutrino mass restricted by low energy obs. n Low scale seesaw à R masses below 10 TeV n µ 3e, µ e + γ, τ 3e etc. bounds restrict flavor structure of R coupling f and hence RHN mass texture!! n One (only) allowed texture: M N = M N = fv R 0 M 1 0 M M 2

20 Understanding small nu mass n Neutrino Mass texture: m D = n Sym limit m D1,2,3 m 1 δ 1 1 m 2 δ 2 2 m 3 δ 3 3 i, δ i 0 δ i, à i m i n sym. Br. à for TeV M R, à small M N = n Small δ, arise from one loop SUSY breaking effects; Good fit to neutrinos (Dev, Lee, RNM 13) 0 M 1 0 M M 2 GeV Y ν m ν = m D M 1 R mt D =0 m ν

21 Experimental searches for TeV W R effects n Collider searches for W R and N: LHC (i) Direct WR production (ii) ν -N mixing from seesaw = (Han, Ruiz et al; Senjanovic, Nemevsek, Nesti, Tello,..Deppisch, Dev, Pilaftsis;..Del Aguila et al.) n New leptophilic Higgses: (Chakrabortty,Gluza, Bhambaniya, Zafron,..Dutta, Goa, Ghosh,Eusebii, Kamon ) n Neutrinoless double beta decay and LFV (Das, Deppisch, Kittel, Valle; Dev, Goswami, Mitra;.) ++, + V N n Light N s and displaced vertices (Helo, Dib, Kovalenko,Ortiz,) mν M N

22 WR search at LHC N l ± jj (Keung, Senjanovic 83) n Golden channel: i k jj ; n Probes RHN flavor pattern: A + + jj M 1 N,ik

23 Current LHC analysis: only W R graph n Current W R limits from CMS, ATLAS 2.9 TeV; n 14-TeV LHC reach for M WR < 6 TeV with 300 fb -1 n A recent CMS excess in ee channel (next page)

24 Intriguing excess in CMS n. CMS: arxiv: n Possible M WR =2.1 TeV? : (Deppisch Gonzalo,Patra,sahu,Sarkar; Heikinheimo, Raidal, Spethman; Aguilar-Saavedra, Joachim;Fowlie,Marzola 14; Gluza, Jelinsky 15)

25 ATLAS Diboson anomaly n Another W R decay mode: W R à W L Z (via WL-WR mixing) n Could it be connected to ATLAS diboson anomaly around 2 TeV? arxiv: n Anomaly in Wh channel (Hisano et al. Dobrescu, Liu; Gao, Ghosh,Sinha,Yu; Cheung et al)

26 New (RL) contribution to like sign dilepton signal V N n When, new contributions: (Nemevsek, Tello, Senjanovic 12; Chen, Dev, RNM arxiv: PRD) q q W R + N; N W L n Flavor dependence will probe Dirac mass M D profile:

27 Higher Mass WR probe at Future Circular colliders n So far one study by Rizzo: W R + ν channel s = 100 TeV Reach: M WR < 30 TeV s = 80 TeV n For the ± ± jj channel, see Ng, Puente,Pan 15

28 New contributions to ββ 0ν n Now >10 25 yr. Future >10 28 yr

29 Cosmology and ββ 0ν n n Low WR effect could fake IH or appear in in the forbidden area

30 LHC and double beta reach n Dev,..

31 Constraints RH Neutrino M N in the lower mass range NA K --> e " V e PS 191 L3 DELPHI ! --> e " CHARM 0"## most relevant for seesaw m 4 (GeV) Bounds from LHC Higgs decay to e + e E T (Dev, Francischini, RNM 12 ; Gago,Hernandez,Perez,Losada,Briceno 15) (Atre, Han, Pascoli, Zhang) from pp h N N W +,Z + ν

32 Beam Dump searches n Displaced vertices (Castillo-Feliosela, Helo, Dib, Kovalenko, Ortiz 15) n M N <1.8 GeV SHIP setup n Reach: M WR 18 TeV

33 Understanding origin of matter with TeV scale L- violation!

34 Does Leptogenesis work in TeV W R models n Since m ν (Y κ)2, TeV v R means Y fv R n Vertex diagram n B CP Im(Y Y ) 2 4πY Y n since ( =wash out) n γ 10 2 CP κ eff κ eff n Vertex diagram does not workà resonant leptogenesis

35 TeV scale Resonant leptogenesis: n RH neutrino mass ~ TeV scale n + n n n B n γ ImY 4 Y 2 n B /n γ Generic model requires degenerate RHNs to get enough n Deg. Natural with our texture: M N = 0 M 1 0 M M 2

36 Final baryon asymmetry from lepton asymmetry n Wash out effect important: (Buchmuller, Di Bari, Pliumacher) n B n γ n In LR, 10 2 CP κ eff κ eff Γ D/Γ S 1 1+Γ D /Γ S Γ D Y 2 Γ S M 4 W R n Given Y, Washout increases as M WR decreases: à lower bound on M WR n Two papers: small Y: M WR >18 TeV (Frere,Hambye, Vertongen) Larger Y with nu fits:m WR > 10 TeV (Dev, Lee, RNM. 14)

37 Case of M N > M WR n CP conserving decay mode dominates! N W R + n Leptogenesis impossible (Deppisch, Harz, Hirsch 14) n If experimentally it is found, M N > M WR, this by itself can rule out leptogenesis as a mechanism for origin of matter!!

38 Summary n TeV scale seesaw is theoretically appealing, can explain neutrino masses contrary to common lore! n Left-Right theories provide a simple realization with testable collider implications (W R, Z, N, ++ )! n Minimal susy LR-rational requiresà M WR < multi-tev R n Leptogenesis bound on W R à M WR > 10 TeV n If colliders find W R with mass < 10 TeV or M WR < M N or light N, leptogenesis can be ruled out. n Further impetus to search for W R!

39 Thank you for your attention!

40 LHC anomalies (~2 TeV) n 3.4 σ WZà JJ excess (ATLAS) n CMS JJ excess 1.8σ excess n 2.2σ Wh excess (ATLAS) n 2.8σ eejj excess (CMS) n 2.6σ excess WW and ZZ channel (ATLAS)

41 LHC anomalies and LR interpretation (~2 TeV) n 2 TeV W R : σ(w R ) B WR WZ 600g 2 RBfb n If no leptons à M Ne,µ M WR n WZ channel signal at the level of 6-7 fbà arises from W L W R mixing, corresponds to ζ LR 0.01 n Signal fits for g R ~ 0.5 g L à ~8 excess events n Predicts ~2-3 excess events in the Wh 0 channel consistent with CMS excess for this channel. n Should not see any signal in WW and ZZ mode. jjjj b bν

42 Leptogenesis with M Z << M WR n Effective theory: SU(2) L U(1) I3R U(1) B L n Z couples also to NN and effects leptogenesis n Origin of CP asymmetry same as in WR case via resonant leptogenesis and requires deg N 1,2 : ε can be as large as 1. n Washout has no W R contribution but only NNà Z à qq, ll type. n Lower the Z, more washout in generic case

43 Lower bound on M Z n (Blanchet, Chacko, Granor, RNM 2009, PRD) n M Z > 3 TeV

44 Directly probing leptogenesis in Z case: ε n Lepton asymmetry is directly related to the following collider observable: n Makes it possible to see origin of matter directly.

45 Distinguishing different mechanisms (RR vs RL) n.look for end points in various inv. Masses: (Kim, Dev,RNM 15)

46 M WR vs M N Plot for one model for leptogenesis n. &# n mw R %*+,& %$ %#!$!# Y -(- Y -(- Y -(- '#"& '! '& 4-5(6)./12(3-.+/0./12(3- M WR >10 TeV M N > 585 GeV Explicit models with nu mass fits. m N ( m W R $!!"#!#"$ #"# #"$!"# '()!# "m N #*+,$

47 Low scale Leptogenesis Plot M WR >10 TeV M N > 585 GeV (Dev., Lee and RNM 15)