Baryogenesis Confronts Experiments, Chicago, Nov. 7-9, 2007

R. MohapatraUniversity of Maryland

K.S. Babu, R.N. Mohapatra, S. Nasri, Phys. Rev. Lett. (2007)K.S. Babu, R.N. Mohapatra, S. Nasri, Phys. Rev. Lett. (2006)

Post-Sphaleron Baryogenesis andNeutron Oscillation ( )NN

Sakharov conditions for Origin of Matter

--Baryon number violation;• CP violation• Out of Thermal Equilibrium (1967)

• Raised the possibility that protons must be unstable or in some other form .

• Mid- 70’s- GUT theories had proton decay and scenarios for baryogenesis

• Started intense search for proton decay.

0B

Things changed in 80’s

•Two developments:

• Rise of Sphalerons in SM;

• Inflationary Universe:

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.

Sphalerons 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 !!

--New scenarios for electroweak baryogenesis were developed:

--Connection between Origin of matter and existence of observable lost ?

122 1010

0B

Leptogenesis: No GUTsNeeded

• 1979: Seesaw mechanism for small neutrino masses were proposed;

• Heavy RH Majorana neutrinos• 1986: Leptogenesis proposed

• Produces lepton asymmetry and sphalerons convert it to baryons.

• No Observable baryon violation needed!

Inflation and GUT baryogenesis

• Final blow to GUT baryogenesis:

• Difficulty of accomodating GUT baryogenesis with inflation- since typical reheat temperatures less than GUT scale !

• How to test baryogenesis experimentally if no connection to ? 0B

Confronting Baryogenesis with Expt.

• Weak scale baryogenesis- one way; e.g. Higgs mass, sparticle properties;• (Carena,Quiros, Wagner,Morrissey, Menon –other talks)

• This talk: Are searches for baryon non-conservation relevant to understanding the Origin of Matter?

• YES ! And the B-violating process is not proton decay but

neutron-anti-neutron oscillation .

Reasons to search for new mechanisms

• Leptogenesis is attractive because it goes naturally with Seesaw mechanism for neutrino masses in SUSY GUTs

• but has issues – • Possible conflict with reheat temp.; • Hard to test except in specific

models.

Issues with Leptogenesis models

• In typical scenarios, lightest RH neutrino mass higher than

• (Davidson, Ibarra)(Resonant case exception-Pilaftsis)

• The upper bound on T-reheat for generic TeV gravitinos is < GeV ;

• (Kohri, Mori,Yotsuyanagi )

Conflict for SUSY

Leptogenesis !!

9103NM

610

Post-sphaleron baryogenesis:

•Basic Idea:• Baryogenesis occurs after Sphalerons

decouple: GeV;• Need new particle with mass ~100 GeV to

TeV; decaying 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

S couplings

RRRRRR ddudduS6

Typical

Explicit Model

80,,MarshakRNM

Embedding into PS Model

• G =• Fermions:

• Higgs:

•

• of our model.

cRL SUSUSU )4()2()2(

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

RLF ,

ZYXR ,, S

cccccc lllqqq ,,

Details:

• (1,3,10) 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.

..chLRFfFL RRRY

....'''''

LBvcc

Mass scales and N-N-bar oscillation

• Delta^4 contains SXXY, SXZZ int.• NN-bar diagram (RNM,Marshak,80)

• Present limits on NN-bar -> 1 -100 TeV or less depending on f-couplings.

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 .S

R

M

T

2/11 ][ PS MT

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][][

][4

*22*

ffTrhhTrM

gffgMMhhTr

S

Tud

T

810

Model Predictions :Class (ii) Diagrams

)(

][Im

4 42

ggTrm

MVMgVMMgTr

W

duduT

B

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

•Gives 810B

Predictions:

• Actual prediction:

CASE

• Extra constraint for the 224 model:

• ; M_S still in the same mass range.

• In general, the model predicts:

• Colored scalars ~1-3 TeV range- partly in LHC reach.

• Puts upper bound on N-N-bar Osc.

Time

cRL SUSUSU )4()2()2(

RNS MM

Confronting Experiments

• Observable Neutron-anti-neutron oscillation:

• Light diquark Higgs- could be observable at LHC for generic scenario

• Light RH Majorana neutrinos- LHC but not observable at present.

Neutron-Anti-neutron Oscillation

• Feynman Diagram contributing:

• Gives • N-N-bar transition time:

ccuuY

ccddX ,ccuu

Y

6

3

M

SfG NN

6QCDNNGm

NN

NNNN m

Constraints on NNbar transition time

• Two parameters of the model: MS and MX constrained as follows:

• Decay Temp above 1 MeV and below 100 GeV;

• MS cannot be too large since this gives more dilution of asymmetry:

• Net effect, if all couplings of X,Y,Z are of same order, upper bound on NN-bar osc time for 4

111111 10~~ ghf

Quantitative Details

• Define:

• Constraints for adequate baryogenesis:• Dilution constr. •

• Post sphal. Constr.

2/1

100;

GeV

M

M

M S

X

S

01.0S

d

M

T 02.06

5.06

1

Plausible Range for NN

.sec1010 1211 NNRoughly

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

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)

Diquark Higgs at hadron colliders through cc or anti-c anti-c annihilations

We concentrate on the final states which include

at least one (anti-) top quark

Top quark with mass around 175 GeV electroweakly decays

before hadronizing, so can be an ideal tool to prove new physics!

c

c

c

c

So, our target is

These processes have no Standard Model counterpart!

As a conservative studies, 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 sea quarks:

Conclusion:• Weak scale Post-sphaleron

baryogenesis is consistent with all known observations:

• Requires high dimensional baryon violation.

• Key test is : N-N-bar oscillation search to the level of 10^10 -10^11 sec.

• 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