R. Mohapatra K.S. Babu, R.N. Mohapatra, S. Nasri, Phys. Rev. Lett. 97, (2007) K.S. Babu, Bhupal Dev, R. N. Mohapatra, in preparation. A New way to understand the origin of Matter

Baryon asymmetry of the Universe Universe is full of matter and no anti-matter WMAP value for this: Was it put in by hand at the beginning ? OR Was it created by microphysics during evolution- if so how ?

Sakharov’s conditions: He proposed 3 conditions for generating baryon asymmetry out of microphysics : (1966) Baryon number violation; CP violation; Out of Thermal Equilibrium;

How does it work ? A particle decays to both particles and anti- particles: Generates net excess of baryons. Cond.1+2 If Thermal Eq., reverse process will erase the excess. Hence condition 3.

History Sakharov work for the first time raised the possibility that baryon number may not after all be conserved. i.e. proton must be unstable or there must be some other form of. Mid- 70’s- GUT theories predicted proton decay and provided concrete scenarios for baryogenesis Started intense search for proton decay as well as baryogenesis ! After 25 yrs, no sign of p-decay !!

Things changed in 80’s Three developments: Rise of Sphalerons in SM; Inflationary Universe: Rise of leptogenesis

Sphalerons and B- violation SM violates baryon number due to sphalerons: No need for GUTs for B-violation. Sphaleron induced B-violating operator: Negligible in Lab but Important in early Universe: Can lead to baryogenesis. (Kuzmin, Rukakov, Shaposnikov)

Sphalerons, Inflation and Baryogenesis Sphaleron Interaction rate in Early Univ. In equilibrium between GeV Does affect the baryon asymmetry generated above 100 GeV- in particular, it erases GUT baryon asymmetry produced by B-L=0 conserving interactions as in SU(5) !! Difficulty of accomodating GUT baryogenesis with inflation- since typical reheat temperatures after inflation is less than GUT scale !

Rise of Leptogenesis : Seesaw mechanism for small neutrino masses were proposed; Minkowski;Yanagida, Gell-Mann, Ramond, Slansky; Glashow; R. N. M., Senjanovic Required Heavy RH Majorana neutrinos 1986: Leptogenesis proposed (Fukugita, Yanagida) Produces lepton asymmetry and sphalerons convert it to baryons. No Observable baryon violation needed!

Issues with SUSY Leptogenesis models Has to be a high scale phenomenon to be predictive. In typical scenarios, lightest RH neutrino mass higher than (Davidson, Ibarra) The upper bound on T-reheat for generic TeV gravitinos is < GeV ; (Kohri, Moroi,Yotsuyanagi ) Conflict for SUSY Leptogenesis !!

Post-sphaleron baryogenesis: Could baryogenesis be a lower scale phenomenon and thus avoid these constraints ? Basic idea: (Babu,R.N.M.,Nasri’06) Baryogenesis occurs after Sphalerons decouple: at GeV; Need new particle with mass ~100 GeV to TeV; decays violating B below 100 GeV. New particle- boson (S) or fermion (N); S or N must couple to B-violating current. B-violating processes must go out of Eq. at low temperature.

Possible B-violating couplings Case (i) ) -Present proton decay constraints imply that the mass scale for this is. This implies that these processes go out of eq. around T~. Clearly not suitable for post- sphaleron B-genesis. Case (ii): induced by operator ; -Gives rise to the process neutron-anti-neutron osc. Present limits -> M~10 TeV range. Out of Eq. T~ 100 GeV range. Suitable for post-sphaleron baryogenesis !!

S couplings

How can this happen ? Bottom-up view: What are possible TeV scale mass scalars that could couple to SM fermions without making trouble ? Color quantum no. SM couples to Leads to p-decay SM Higgs Allowed; are they there ?

Explicit Model We will see that these particles are not only allowed by bottom up view but they arise naturally in a class of neutrino models.

B violating decay of S

Out of Equilibrium condition S Decays go out of Eq. around ~ few 100 GEV The S-particle does not decay until After which it decays and produces baryon-anti-baryon asymmetry: The S-decay reheats the Universe to TR giving a dilution of. This dilution effect for our case is not significant.

CP Asymmetry: Two classes of one loop diagrams

Model predictions : Class I diagrams In general Goes down as MX increases and could be small.

Model Predictions : Class (ii) Diagrams Note that even if g’s are real, only CKM phase can give baryon asymmetry. Gives

Quantitative Details Define: Constraints for adequate baryogenesis: Dilution constr. Post sphal. Constr. Easy to satisfy with choice of f-parameters. ; f_33~1; M_s~100 GeV; M_X~300 GeV.

A Theory of Post -Sphaleron Baryogenesis Note: X,Y,Z particles are crucial to this mechanism- what are they ? Neutrino mass throws light on X,Y,Z Seesaw for neutrino mass and left-right symmetry: Seesaw requires RH neutrino and B-L breaking; RH neutrino and B-L automatic in left-right model.

LR Model-A natural framework for seesaw and gauged B-L Gauge group : Fermion assignment Higgs fields Low energy V-A for

Detailed Higgs content and Sym Breaking is responsible for neutrino masses and when generalized lead to qq(X,Y,Z ) couplings.

Symmetry breaking and seesaw for neutrinos If MD small, neutrino mass formula becomes

Embedding into higher symmetry G = Fermions: Higgs: +.. (Marshak, R.N.M., 80) (contains X,Y,Z diquarks) of our model.

Details: (1,3,10) couplings that generalize seesaw couplings: = gives mass to the RH neutrino and does seesaw for neutrino masses. V = V_0 The last term contains the SX^2Y, SXZ^2 terms. =100 TeV; M =TeV or less. Main point is that now we can relate the diquark couplings to neutriono masses via the type II seesaw i.e.

Phenomenological constraints on Yukawacoupling Constraints by rare processes mixing Similarly B-B-bar etc

Details of FCNC constraints: Hadronic:

FCNC and Inverted Neutrino mass pattern Considerably narrows the choice for the coupling matrix f and predictive for neutrino masses and mixings: (Babu,Dev,RNM )

Allowed mass ranges for S and X Allowed masses: Predicts light diquarks;

Baryogenesis Confronts Experiments Neutrinoless double beta decay expts running will test this model. Testing this generic mechanism: (i) Observable Neutron-anti- neutron oscillation: (ii) Light diquark Higgs- could be observable at LHC for generic scenario

Neutrinoless double beta decay: Majorana, EXO, Gerda,NEMO,… Null result to the level of 10 meV will rule this model out.

Neutron-Anti-neutron Oscillation Feynman Diagram contributing: (RNM, Marshak,80) Gives N-N-bar transition time:

Prediction in our model: ; Dominant operator is udsuds type; Need to be combined with Interactions:

Observing Neutron- Anti-neutron Oscill. Phenomenology: Probability of Neutron Conversion to anti-N:

Searching for Free N-Nbar Oscillation Figure of merit = X Running time

Present expt situation First Free neutron Oscillation expt was carried out in ILL, Grenoble France: (Baldoceolin et al, 1994) Expt. Limit: With existing facilities, it is possible extend the limit to:

N-Nbar search at DUSEL  TRIGA research reactor with cold neutron moderator  v n ~ 1000 m/s  Vertical shaft ~1000 m deep with diameter ~ 6 m  Large vacuum tube, focusing reflector, Earth magnetic field compensation  Detector (similar to ILL N- Nbar detector) Kamyshkov et al. Proposal: Reach:

Nucleon instability and N- N-bar Nuclei will become unstable by this N-N-bar interaction; but rate suppressed due to nuclear potential diff. between N and N-bar. Present limits: Sudan, IMB, SK-

Collider Signatures: Of the X, Y, Z, only Y-coupling can have potentially significant collider signature for some range of parameters: -Diquark Higgs at hadron colliders through uu or anti-u anti-u annihilations (Okada, Yu, RNM, 2007)

LHC production These processes have no Standard Model counterpart! As conservative study, we consider pair production in the Standard Model as backgrounds top quark identification To measure diquark mass (final state invariant mass) difficult to tell top or anti-top?

Cross section for tt production: tt and t+jet from valence quarks in model with type II seesaw for neutrino masses:( Direct correlation between neutrinos and diquark couplings) Fits nu-osc data for inverted hierarchy:

Tevatron bound on Diquark Higgs mass Top pair production cross section at Tevatron

Differential cross section as a function of the invariant Diquark has a baryon number & LHC is ``pp’’ machine 

Conclusion: Weak scale Post-sphaleron baryogenesis consistent with all known observations: A new mechanism: Requires high dimensional baryon violation. Key tests a model realization are : (i) Inverted nu mass hierarchy + large theta_13 (ii) N-N-bar oscillation search to the level of 10^10 -10^11 sec. (iii) Collider searches for diquarks can also probe some parameter ranges.

Conclusions contd. In terms of a big picture for unification: Post-sphaleron baryogenesis and NNbar go well with a picture orthogonal to conventional GUT- Tests Int scale B-L models for nu masses; Does not need supersym although it is consistent with it.

Collider Search for Majorana In the 224 model, quark couplings are same as RH neutrino couplings: mass in the TeV range; Mixes with LH neutrinos and therefore can be produced in W-decays; Like sign dilepton + jets and no missing energy signal.

RH Nu Search: Recent work: Han, Zhang (2006) Not easy- mixing too small:

Basics formulas with the total decay width as the sum if each partial decay width No angle dependence

At Tevatron: At LHC : * We employ CTEQ5M for the parton distribution functions (pdf)

Example of couplings satisfies the constraints from rare decay process Tevatron bound on Diquark Higgs mass Top pair production cross section measured at Tevatron

Differential cross section as a function of the invariant LHC Diquark has a baryon number & LHC is ``pp’’ machine 

Angular distribution of the cross LHC SM background Diquark is a scalar  No angular dependence SM backgrounds  gluon fusion  peak forward & backward region