Neutrino Mass Physics at LHC R N Mohapatra

Neutrino Mass Physics at LHC R. N. Mohapatra University of Maryland NO-VE, 2008, Venice

Neutrino mass Physics n n n Neutrino masses and mixings are now facts: we are entering the era of Precision Neutrino Mass Science (PNMS era) There is surely a great deal of physics beyond the standard model associated with this. How can LHC help us to unravel this physics ?

Two broad new kinds of physics for neutrino mass: n n (i) Why ? (new scale, new particles, . . ) (ii) Why two mixing angles are so large ? (new flavor symmetries or GUTs ? )

Small neutrino mass and Seesaw mechanism n n Why ? Seesaw solution: Add right handed neutrinos to SM with Majorana mass: new n Breaks B-L : New scale, new symmetry and new physics beyond SM. After electroweak symmetry breaking leads to seesaw formula:

n After Electroweak Sym Breaking mass matrix is given by Seesaw Mechanism n n which gives (type I seesaw) Minkowski, Gell-Mann, Ramond, Slansky, Yanagida, R. N. M. , Senjanovic, Glashow

Seesaw and B-L symmetry n n SM Higgs boson represents physics of the electroweak symmetry breaking and its discovery will complete understanding of SM symmetry. Seesaw mechanism tells us that there is a new symmetry breaking scale associated with RH neutrino mass: B-L symmetry. This talk discusses how to search for the Higgs fields associated with this symmetry and improve our understanding of B-L symmetry.

Testing the seesaw idea and B-L symmetry. n Important for testing seesaw are two considerations: (i) How big is the seesaw or B-L scale ? (ii) What is the new physics associated with this new scale ? –are there new forces, new Higgs fields, etc ?

Seesaw with no new forces at LHC n If there is no new interaction: Only way to test seesaw is to produce N; This can happen only through mixing if is in sub-Te. V range and further only if mixing is > (del Aguila, Aguilar-Savedra, Pittau; Han, Zhang…) n – However Tiny and 100 Ge. V implies and ; can only be large under highly contrived cases: (Kersten, Smirnov) ; Unlikely to test seesaw this way!

Situation changes drastically with new interactions: n n n With new gauge forces coupled to RH neutrinos, seesaw can be tested despite tiny ; A simple possibility is where there is a B-L gauge force coupling to matter as part of an gauge symmetry. RH neutrino mass in this case is associated with the breaking of this new symmetry. This provides new signals for seesaw at LHC.

Two well motivated scenarios: n n n n (i) Large Grand unification is an independently well motivated hypothesis which suggests for Yukawa coupings: implying Ge. V Gauge coupling unification scale High scale seesaw goes well with GUT s; e. g. SO(10). However in this case, few signals of seesaw: One direct test is search for assuming susy ! GUTs have problems too: doublet triplet splitting; vs

Lower scale non-GUT type seesaw: Subject of this talk: (ii) Small Yukawas: n Note the dependence of in the seesaw formula compared to linear on for ; so not too small Yukawas can lead to e. g. Implies seesaw or B-L physics scale in few Te. V range. n In general scale far below GUT scalen Simple example is - low scale left-right model. n

SUSY LR attractive for other reasons: n n n Supersymmetric left-right model: (i) Expialns the origin of parity violation: (ii) Solves gauge hierarchy problem (as in MSSM); (iii) Gives automatic R-parity (unlike MSSM) and hence natural neutralino dark matter and naturally stable proton. (iv) Solves susy CP and strong CP problem (unlike MSSM). (v) Helps in understanding a supersymmetry breaking mechanism (unlike MSSM).

SUSYLR DETAILS: n Gauge group: Fermion assignment n Higgs fields n (R. N. M. , Senjanovic, 79)

Detailed Higgs content and Sym Breaking Break symmetry and give fermion masses

SUSY essential for lower scale left-right seesaw Without SUSY neutrino mass too large since v_L~Ge. V. (type I+II seesaw) , SUSY implies ; (pure type I

SUSY breaking constraints and sub-Te. V - Higgs n n An important question in supersymmetry is: how is supersymmetry broken ? Scenarios: (i) Minimal Supergravity: FCNC problem (ii) Gauge mediation (needs many particles, does not have cold dark matter etc. ) (iii) Anomaly mediation: (potential to solve both these problems. )(Randall, Sundrum; Giudice, Luty, Murayama, Rattazzi) n Consistency of case iii with electric charge conservation requires sub-Te. V - Higgs

Two cases with LHC signal n n n (i) Multi-Te. V scale WR: In this case, Sub-Te. V to Te. V scale WR, Z’, which can be searched for in colliders: (ii) Higher scale B-L (or WR): New result: If , one will have in the sub-Te. V range and observable. Searching for Higgses can probe B-L scale upto.

Te. V mass WR case: (A): Direct production at LHC n Looking for Te. V scale at LHC : Signal: Very little background; already used in D 0, CDF ; Present limits: 780 Ge. V (Keung, Senjanovic, 83) (Does not depend on ) LHC reach 4 Te. V (Azuelos et al)

(B): Neutrinoless double beta decay n n n Te. V scale WR contributes to nu-less double decay regardless of how small nu- Majorana mass is. (P. Vogel’s talk) Dependence on WR mass is M^-5 – Present bound is ~1 Te. V can go up to 2 Te. V.

(C): New Relaxed Upper bound on light Higgs mass n n n MSSM: Light Higgs mass: Ge. V For Low scale WR, new contribution from Dterm+ 1 -loop Zhang, RNM, Ji, An ar. Xiv: 0804. 0268

Te. V and Higher scale Seesaw and Higgs n n A generic prediction of all these models: doubly charged Higgs and Higgsinos, triplet Higgses ( , )in the Te. V range – without fine tuning. Different from triplet Higgs of type II seesaw models discussed in Perez, Han, Huang, Wang, Li, Si, Akeroyd, Aoki, Sugiyama; …… n Different from usual SUSY models which only have neutral and singly charged Higgs

Doubly charged Higgs: n Very different from known Higgs in that it couples only to leptons and not to quarks: Coupling not small. One coupling to left and another to the right sector: Both decay to lepton pairs (from coupling) n For left Delta, n n

Difference from type II models n n n In type II models, it is only the triplet that is present; its coupling f to leptons depends on the < >=v since So only for e. V vev for f is measurable; Pro: it tracks neutrino mass matrices; Measuring different branching ratios gives neutrino mass matrix Con: such small vevs come out naturally only if triplets are superheavy and beyond the reach of LHC. One needs to do a severe fine tuning (~ ) The models I discuss are not fine tuned:

Difference of type II models from type I: n Type II: decays: n Whereas for type I models we discuss:

Present lower bounds on doubly charged Higgs mass: n n n Drell-Yan pair production main mechanism at hadron colliders: Signal: pp --> or all muon Collider: CDF, D 0: Ge. V HERA > 141 Ge. V Low energy: Muonium-anti-muonium osc. (PSI) For , M++ >250 Ge. V. g-2 of muon: 100 Ge. V order.

Production process: n n n Drell-Yan via exchange; Signal: peak in like sign lepton invariant mass plot for double charged case; trilepton + missing E in case.

LHC prospects: n Gunion, Loomis and Petit; Akyroid, Aoki; Azuelos et al. , Mukhopadhyaya, Han, Wang, Si; Huitu, Malaampi, Raidal; Dutta. . n Main Bg ZZ production: LHC Mass Reach ~Te. V with 300 fb^-1.

Doubly charged Higgs and muonium-antimuonium Osc. : n Muonium-anti-muonium can provide better probe for some models: If SUSY is broken by anomalies: and also M < 10 Te. V. n Lower limit on n PRISM expt. Reach: n n

Doubly charged Higgs at Collider collider at 1 Te. V cm E can probe doubly charged Higgs upto 900 Ge. V mass. (Mukhopadhyay, S. Rai) n. The relevant processes: n n

Singly charged n n signal Properties of singly charged different from MSSM singly charged couples only to leptons- has L=2 Present bound on mass comes from wrong kind of muon decay: and nu. Te. V expt looking for

Bounds on n Nu. Te. V bound (Formaggio et al, 2001) Mass bound in 100 Ge. V range for reasonable values of f-couplings. New proposal NUSONG expt (Conrad et al. 2007) will improve this limit by a factor of 4.

AT LHC n LHC signal: pp n K. Wang et al. n + missing E

Why are naturally light even for high scale seesaw ? (i) If LR scale is less than few Te. V , clearly these Higgs can have in the sub. Te. V mass. n (ii) For higher scale seesaw accidental global symmetry leads to sub-Te. V as long as or less. (iii) If SUSY is broken by anomaly mediation, these fields with sub-Te. V to Te. V masses become essential to avoid electric charge non-conservation. Strongest case for light. n

n n n Basic point is the constraint of supersymmetry: SM Minimum corresponds to: Conserves electric charge. Higgs mass prop to and hence Higgs mass arbitrary. Bring in Supersymmetry: and hence an upper limit on Higgs mass <130 Ge. V. For SUSYLR seesaw models, SUSY constrains the Higgs potential so much that Necessary consequence is light below 10 Te. V. Otherwise, electric charge broken by vacuum.

Light scale n n Higgs for High seesaw Naïve logic: Higgs mass is of the order of symmetry breaking scale; breaks down when there accidental symmetries. SUSYLR superpotential: Has U(6, c) global symmetry which breaks down to U(5, c) (in the absence of higher dim term. ) eleven massless complex Higgs bosons: 3 absorbed in gauge sym. breaking from SU(2)x. U(1) to U(1). Eight left are two doubly charged Higgs bosons and two SM triplets;

How do n n n get masses ? The nonrenormalizable term Where could be the new physics scale above WR scale or Planck scale. Breaks this enhanced global symmetry and give mass to fields. n Mass is of order: n implying for Delta mass sub. Te. V. (Aulakh, Melfo, Senjanovic; Chacko, RNM, 97) n Observation of below GUT scale. ; probes seesaw scale far

Anomaly mediation and light Squark and slepton masses in AMSB: o. So for the case of MSSM+AMSB, slepton mass squares negative-vacuum

Slepton masses in SUSYLR +AMSB Where f is the Yukawa coupling and g is the generic gauge coupling: slepton masses become positive if SUSYLR cures the tachyonic slepton problem of AMSB without fine tuning assumptions: (Setzer, Spinner, RNM, Phys. Rev. D and ar. Xiv: 0802. 1208 - JHEP )

Limit on Higgs mass, couplings from detailed study: n For AMSB cure to work, we must have n (i) n (ii) n n This implies Prism proposal: ; also triplets.

Bunched Sparticle spectrum

Summary and Conclusion: n n n Minimal SUSY seesaw in conjunction with a way to understand SUSY breaking (AMSB) predicts the existence of sub-Te. V They can be observable in LHC as well as in muonium-anti-muonium oscillation experiments. In particular it predicts: Search for Delta Higgses can probe seesaw below

Summary and Conclusion: n (i) < few Te. Vs or n (ii) > n n Ge. V ; (iii) If SUSY is broken by anomaly mediation, then Ge. V (iii) In these models, there are 100 Ge. V to Te. V scale SU(2)-triplet and doubly charged Higgs fields. (iv) Case (i)- Upward shift of light Higgs mass

Range of Double charged Higgs masses n n Upper limit for AMSB to work: Lower limit on muonium-anti-muonium oscillation amplitude for this model (PSI) Higher precision search for important. Te. V scale WR models have many collider tests: e. g. Higher Higgs mass, like sign dilepton events and of course sub-Te. V scale doubly charged Higgs

Dark matter issue: n Neutralino unstable ! But gravitino though unstable due to R-P breaking but still quite long lived to be dark matter: Decay diagram: n Longer than the age of the universe ! n n (Ibarra, et al)

Displaced vertices: n n Neutralino decays but with a nano to pico sec. lifetime; hence leads to displaced vertices: (Zhang, Nussinov, et al. to appear)

Constraints on WR in SUSYLR : Theory details n Higgs superfields break SU(2)_R n V=V_F+V_D+V_S (V_F, V_D >0) n Look for minimum of the potential

n n What is the smallest value of the D-term ? When is =0 Since in general n If RP conserved i. e. V is minimum when V_D vanishes and that occurs when: since n But this breaks electric charge ! n n

Charge conservation -> RP violation So only choice left to get a charge conserving minimum is when n It breaks R-parity and Lepton number but not Baryon number. So proton stability is guaranteed. Corollary: Seesaw scale has an upper limit of a few Te. V. (Kuchimanchi, RNM, 95)

Why n n Ge. V ? As the seesaw scale increases, higher dim terms in superpotential become important : restore R-parity and give a stable charge conserving vacuum: Typically, they are (if no new physics till Planckotherwise replace by new Phys scale) + Lower limit on WR when above terms are of order weak scale i. e. >

How do they get masses ? n The second nonrenormalizable term breaks this enhanced global symmetry and give mass to fields. n Mass is of order: implies Ge. V implying n (Aulakh, Melfo, Senjanovic; Chacko, RNM, 97) n ; LEP bound then v_R

Range of Double charged Higgs masses n n n Upper limit for AMSB to work: Lower limit on muonium-anti-muonium oscillation amplitude for this model (PSI) Higher precision search for important.

LHC signals of low scale seesaw n (i) Te. V scale Signal: : Very little background; already used in D 0, CDF ; Present limits: 780 Ge. V (Keung, Senjanovic, 83) n (ii) I will focus on Higgs boson tests

Signals for Te. V scale WR’s etc. n First issue: Is there a dark matter ? Yes. It is the gravitino; it is unstable due to R-P breaking but still quite long lived. Decay diagram: n Longer than the age of the universe ! n n