NNbar programNNbar program::

• 3:30-5:30• R. N. Mohapatra: 3:30-4:00 (25+5)

What physics from NNbar ?• K. S. Babu: 4:00-4:25 (20+5)

Origin of matter and NNbar• R. Shrock: 4:25-4:50 (20+5)

Extra D and NNbar• Y. Kamyshkov: 4:50-5:10 (15+5)

Experimental issues• Discussion 5:10-5:30

Working group members Working group members

• K. S. Babu• Z. Berezhiani• A. Dolgov• G. Gabadadze• A. Gal • Y. Kamyshkov• B. Kopeliovich• R. N. Mohapatra• R. Shrock

……………..

What can N-N-bar Oscillation What can N-N-bar Oscillation teach us about physics teach us about physics

Beyond the standard model ?Beyond the standard model ?

R. N. MohapatraUniversity of Maryland

DUSEL Theory Workshop, Columbus, Ohio; April 4-6,2008.

Particle oscillationsParticle oscillations

• Oscillations of quantum mechanical states is a familiar phenomenon in Nature.

• In particle physics, electrically neutral particles e.g. Kaons and neutrinos have been observed to oscillate, teaching us a great deal about the fundamental forces and matter.

• Neutron is another neutral particle- it could oscillate to anti-neutrons. What can it tell us about physics beyond the standard model ?

Neutron-anti-neutron OscillationNeutron-anti-neutron Oscillation::

• Violates baryon number by two units:

• Any Indication of B-violation in Nature ?

(i) Standard model has B-violation (but it leaves B-L symmetry exact and B-L is emerging as an important new symmetry of Nature ) !!

(ii) Understanding the origin of matter requires B-Violation and often involves B-L violation !!

(iii) Most physics scenarios of physics BSM have B-violation e.g. Grand unified th.

B-L : new symmetry in B-L : new symmetry in Nature ?Nature ?

• What happens to B-L symmetry beyond standard model ?

• Remain exact or gets broken ?• If broken, what is the scale of its

breaking ?• Physics associated with this

breaking e.g. is B-L part of GUT ?• Two expts that can probe it directly

are and N-N-bar oscillation.0

Neutrino Mass and B-L=2Neutrino Mass and B-L=2• If neutrino is Majorana particle, it

breaks B-L by two units; observation of decay will confirm this but by itself will not tell us much about new physics associated with (B-L).

•N-N-bar observation MAY supply this information !!• (with normal nu-hierarchy, may be very

difficult to observe leaving NNbar as only way)

0

0

Neutrino mass-NNbar connectionNeutrino mass-NNbar connection

• Majorana neutrino -> implies (B-L)=2;• In quark-lepton unified theories B and L get

connected and L=2 implies B =2 via B-L symmetry and hence N-N-bar oscillation.

• There are reasons to think that there may be quark lepton unification at high energies.

• Discovery of neutrino mass therefore provides a very strong motivation to search for N-N-bar oscillation, which can be new window to Q-L unification as well as B-L symmetry.

Questions for N-N-bar oscillationQuestions for N-N-bar oscillation

• Can the possible reach of N-N-bar oscillation time in existing facilities probe interesting range for new physics indicated by neutrino mass ?

- Are there decent theories EMBEDDING small neutrino masses where scale N-N-bar oscillation is observable?

• Is it cosmologically safe to have observable N-N-bar oscillation ?

• The answer to all these questions is YES .

March 2005Theme Group 2

Phenomenology of N-N-bar OscPhenomenology of N-N-bar Osc

n

n

Vm

Vm

n

n

ti

2

1

tVVSinVV

P nn )( 212

2

21

Two :cases:1))(( 21 tVVi

2

nnnn

tP

1))(( 21 VVii

2

21

VVP nn

t

Present expt situation in N-N-bar OscPresent expt situation in N-N-bar Osc..

Range accessible to current reactor fluxes: Present limit:ILL experiment: Baldoceolin et al. (1994)

New proposal (Y. Kamyshkov et al.) for an expt. In DUSEL

GOAL:

Figure of merit ~

.sec108 nn

10 > 10 sec.n n

2

nn

tFlux

8 11~ 10 10 sec.n n

or factor 1,000-10,000in appearance probability

Could proton decay set-up be used to Could proton decay set-up be used to discover N-N-bar ?discover N-N-bar ?

• Nuclei will become unstable with N-N-bar interaction; but rate suppressed due to nuclear potential diff. between N and N-bar. (Gal et al; Alberico et al; Kopeliovich et al.)

• Present limits:• Sudan, IMB, SK-

• Nuclear Uncertainties !• Atmos, Bg makes

discovery reach very limited

freeNuc R 2 123 sec105.0 R

Could Proton decay set-up be used to discover NNbar ?

8~ 3 10 s

Mass scales probed by N-N-barMass scales probed by N-N-bar

To see what is probed by N-N-bar, do operator analysis for processes:

2BO cccccc ddudduM 5

1

62 QCDBnn Om

5~/ Mm nnnn 6/

giving .sec10~ 8nn GeV5.510

2B

M

Note M5 suppression

Scale Reach of N-N-barScale Reach of N-N-bar

• Is the scale reach of N-N-bar limited to only 300 TeV in generic models as suggested ?

• NO- once new physics at TeV scale is entertained e.g. SUSY, new Higgs !

Weaker suppression with SUSYWeaker suppression with SUSY

A. Dominant operator with SUSY:

B. SUSY + diquark Higgs field , at TeV scale

ccuu

Can probe M_B-L upto

109 GeV

Probe M_{B-L} to 1012 GeV.

theory For N-N-bar theory For N-N-bar • Neutrino mass points to New

electroweak symmetry with B-L• Gauge group: Left-right sym th.

• Fermion:

• New approach to observed parity violation i.e. it is only a low energy phenomenon !!

• The true weak interaction theory is parity conserving like strong, EM and gravity !!

LBRL USUSU )1()2()2(

L

L

d

u

R

R

d

u

L

L

e

R

R

e

P P

scale of new B-L physics ?scale of new B-L physics ?

One attractive possibility suggested by coupling constant unification is that it is GeV.

Local B-L is part of a grand unifying symmetry and it breaks at GUT scale. Related physics is GUT physics. Group: SO(10)

1610

Alternative B-L UnificationAlternative B-L Unification• New physics below GUT scale• Only 16 fermions unified but not gauge

couplings:

(Pati, Salam, 73)

Only restriction on B-L scale is nu mass (not coupling unification) and hence

-even 100 TeV

N-N-bar is an effective probe in this case;

cRL SUSUSU )4()2()2(

GeVGeVM 1611224 1010

Non-SUSY G(224) and N-N-barNon-SUSY G(224) and N-N-bar• The Feynman diagram for N-N-bar in Non-

SUSY 224 model (RNM, Marshak, 80)

• vertex needed for baryogenesis .• With M= N-N-bar

observable only if

5~/ Mm nnnn

6/5~/ Mm nnnn

LBMM GeVM LB65.510

4

Origin of matter in N-N-bar Origin of matter in N-N-bar modelsmodels

• Popular scenarios: e.g. leptogenesis have baryon asymmetry generated at very high temperatues;

• Observable N-N-bar -> remains in equilibrium down to TeV Temp: erases this asymmetry;

• Discovery of NNbar osc will point to radically new way to understand the origin of matter

One example of such a scenario: Baryon asymmetry after sphaleron decoupling: In the context of 224 model, it is the late decay of field that can create baryons using the CKM phase.

Post-sphaleron baryogenesis: Babu,RNM, Nasri PRL, (2006,2007);

(BABU’s talk)

0

.sec1010 1211 NNRoughly

Baryogenesis upper limit on Baryogenesis upper limit on NNbar Osc time.NNbar Osc time.

Preliminary conclusion:Preliminary conclusion:

• Non-SUSY G_224 model with ~100 TeV B-L scale is a completely self consistent alternative to usual GUT scenarios !!

• No proton decay problem- NN-bar observable and has an upper limit !

• Could imagine solving gauge hierarchy problem via extra dim scenarios !!

Estimate of N-N-bar in SUSY 224 model:Estimate of N-N-bar in SUSY 224 model:

• New Feynman diagram for N-N-bar osc.

N-N-bar osc can probe MB-L~1011 GeV (Dutta, Mimura, RNM; PRL (2006)

Proton decay vs N-N-bar oscillationProton decay vs N-N-bar oscillation

Other Theories probed by N-N-barOther Theories probed by N-N-bar

• N-N-bar is also observable in generic low gravity scale extra dim. Models:

• (Nussinov, Shrock; Dvali, Gabadadze; Dolgov, Bambi; )

• N-N-bar expt could also probe mirror sector of the Universe by searching for N-N’ oscillation:

- Current limits ~400 sec.• (Bento, Berezhiani, 2005)

• Berezhiani’s Talk: MIRROR WORLD• Lee and Yang, parity paper (1957)

A bit more on N-N’ Oscillation:A bit more on N-N’ Oscillation:

What is a mirror neutron ?What is a mirror neutron ?

• u’d’d’=n’ mirrror neutron

n-n’ oscillation n-n’ oscillation

• Phenomenology: very similar to n-n-bar case:

Present status of searchPresent status of search

So Why do N-N-bar search ?So Why do N-N-bar search ?• If neutrino are Majorana, it implies B-L=2 and it is

important to know the scale of B-L breaking. Neutrino mass by itself does not give us this information.

• If there is quark lepton unif., N-N-bar oscillation exists and can probe the scale and physics associated with B-L.

• Search at 1010 sec level will test for (B-L) (seesaw) scale < 1011 GeV vs GUT seesaw.

• NNbar discovery will fundamentally alter our thinking about:

(i) grand unification; (ii) Origin of matter; (Babu) (iii) constrain CPT violation, extra dim. (iv) N-N’ to throw light on dark matter.

Thank you for your attention.

Discussion points:Discussion points:

• Physics issues- mass scale probed

• Cosmology

• Nuclear physics

• Experiment

nuclnn vs 2

ConclusionConclusion

• With the discovery of neutrino mass the case for N-N-bar oscillation is a lot stronger now than before. Urge new search at the level of >1010 sec to test for (B-L) (seesaw) scale less than 1011 GeV vs GUT scale seesaw.

• N-N-bar discovery will completely change the thinking on grand unification.

• Baryon asymmetry consistent with NN-bar;

Upper limit on NN-bar time in some cases.• Reactor oscillation search much better than

decay searches due to nucl. uncertainties !!

Thank you for your attention.

B-L- Grand unificationB-L- Grand unification• SO(10) : the minimal GUT theory with

B-L motivated by Gauge coupling unification:

• All fermions unified to

one {16} dim rep.• (Georgi; Fritzch, Minkowski)

• B-L violation scale is GUT scale

due to unification. N-N-bar

suppressed and unobservable.

Nucleon Decay in Generic SignatureNucleon Decay in Generic Signature

• Key test of GUTS: Gauge Boson mediated p-decay:

Origin of MatterOrigin of Matter• Possible scenarios:

• Leptogenesis:

• Hard to test at low energies: Strictly No connection to neutrino mass phases;

• Electroweak baryogenesis: • Higgs mass < 120 GeV. Testable.

Baryogenesis upper limit onBaryogenesis upper limit on

• Scenario for NON-SUSY 224 model ( )

• S has B=2 coupling; • 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 which should not too small.

These put an upper limit on NNbar time (Babu’s talk)

NN

2/11 ][ PS MT

ccS Re

S

R

M

T