R. Mohapatra

K.S. Babu, R.N. Mohapatra, S. Nasri, Phys. Rev. Lett. 97,131301 (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 ?

1010)15.02.6(

n

nn BBCMBB

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.

nqX qn

)1( R

)1( R

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 !!

0B

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 !

122 1010

Rise of Leptogenesis• 1977-79: 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 !!

9103NM

610

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.

200T

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 !!

2/M

GeV1510

GeV1510

5/Mdduddu cccccc

S couplings

RRRRRR ddudduS

6Typical

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.*}6,6{*}3,3{}1{

SM

couples to

,..uQ QLQQ, 6)(QQ

•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.

sextets

B violating decay of S

22

13 )()/100( hgMGeV 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.S

R

M

T

2/11 ][ PS MT

*g

CP Asymmetry:Two classes of one loop diagrams

)(i

)(ii

Model predictions: Class I diagrams

• In general

• Goes down as MX increases and could be small.

B

810

][][

][4

*22*

ffTrhhTrM

gffgMMhhTr

S

Tud

T

Model Predictions :Class (ii) Diagrams

•Note that even if g’s are real, only CKM phase can give baryon asymmetry.

•Gives 810B

)(

][Im

4 42

ggTrm

MVMgVMMgTr

W

duduT

B

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.

2/1

100;

GeV

M

M

M S

X

S

02.06

5.06

1

GeVTd 12.0

4111111 10~~ ghf

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

LBRL USUSU )1()2()2(

L

L

d

u

R

R

d

u

L

L

e

R

R

e

P P

)0,2,2( )2,1,3()2,3,1(; LR

ZWZW LRMM

,',

Detailed Higgs content and Sym Breaking

021

20

1

2

12

1

0

'0

0

0

00

Rv

RLfLLRLhQQhL LudeRduLduY ,,,,

is responsible for neutrino masses and when generalized lead to qq(X,Y,Z ) couplings.

Symmetry breaking and seesaw for neutrinos

LBRL USUSU )1()2()2(

YL USU )1()2(

0 R

'0

0

emU )1(

0;0, , lqZW mMML

Rfv0

00

R

L

fvh

hfv

DRDT

L MMMfvm 1If 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.

cRL SUSUSU )4()2()2(

)10,3,1()15,2,2();1,2,2( R

RLF ,

ZYXR ,, S

Details:• (1,3,10) couplings that generalize seesaw

couplings:

• <S>= 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.• <S>=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.

..chLRFfFL RRRY

....'''''

LBvcc

Phenomenological constraints

on YukawacouplingConstraints by rare processes

mixing

KK

Similarly B-B-bar etc

cd

cd

cs

cs

... cj

ciddij ddf cc

exchangeccuu

cdcd

Details of FCNC constraints:

• Hadronic:

e

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)

eV)03(.

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:

ccuuY

ccddX ,ccuu

Y

6

3

M

SfG NN

6QCDNNGm

NN

NNNN m

Prediction in our model:

011 df

2S

529

51518

5

22412

211

10~

1010

101.0~

GeV

GeVGvMM

ffG RW

SRXY

ddud

NN

; Dominant operator is udsuds type; Need to be combined with

Interactions:

.sec10~ 9nn

Observing Neutron-Anti-neutron Oscill.

•Phenomenology:

• Probability of Neutron Conversion to anti-N:

n

n

Vm

Vm

n

n

ti

2

1

tVVSinVV

P nn )( 212

2

21

:1))(( 21 tVVi

2

nnnn

tP

1))(( 21 VVii

t 2

21

VVP nn

Searching for Free N-NbarOscillation

Detector

100 MWHFIR

reactor

ColdNeutron

Moderator

reactor core

vacuum tubemagnetic shieldfocusingreflector

beamdump

annihilation target

2.3 m

L ~ 200 - 500 m

2

#

nn

transitn

tN

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:

.sec108 nn

.sec1010~ 118 nn

N-Nbar search at DUSEL

TRIGA research reactor with cold neutron moderator vn ~ 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:

.sec1010 1110

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-

freeNuc R 2 123 sec103.0 R

.sec102~ 8

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 mass@LHC

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.

R

R

RH Nu Search:

• Recent work: Han, Zhang (2006)

• Not easy-• mixing too small: RN

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 processTevatron bound on Diquark Higgs mass

Top pair production cross section measured at Tevatron

Differential cross section as a function of the invariant mass @ LHC

Diquark has a baryon number & LHC is ``pp’’ machine

Angular distribution of the cross section @ LHC

SM background

Diquark is a scalar No angular dependence

SM backgrounds gluon fusion peak forward & backward region

)(

][Im

4 42

ggTrm

MVMgVMMgTr

W

duduT

B