1. NNbar 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

2. Working group members K. S. Babu Z. Berezhiani A. Dolgov G. Gabadadze A. Gal Y. Kamyshkov B. Kopeliovich R. N. Mohapatra R. Shrock ……………..

3. What can N-N-bar Oscillation teach us about physics Beyond the standard model ? R. N. Mohapatra University of Maryland DUSEL Theory Workshop, Columbus, Ohio; April 4-6,2008.

4. Particle 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 ?

5. Neutron-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.

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

7. Neutrino 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)

8. Neutrino 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.

9. Questions 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.

10. March 2005 Theme Group 2 Phenomenology of N-N-bar Osc

11. Present 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 ~ or factor 1,000-10,000 in appearance probability

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

13. Mass scales probed by N-N-bar To see what is probed by N-N-bar, do operator analysis for processes: Note M 5 suppression

14. Scale 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 !

15. Weaker suppression with SUSY A. Dominant operator with SUSY: B. SUSY + diquark Higgs field, at TeV scale Can probe M_B-L upto 10 9 GeV Probe M_{B-L} to 10 12 GeV.

16. 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 !!

17. 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)

18. Alternative B-L Unification Alternative 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;

19. Non-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

20. Origin of matter in N-N-bar models 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)

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

22. 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 !!

23. Estimate of N-N-bar in SUSY 224 model: New Feynman diagram for N-N-bar osc. N-N-bar osc can probe M B-L ~10 11 GeV (Dutta, Mimura, RNM; PRL (2006)

24. Proton decay vs N-N-bar oscillation

25. Other 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)

26. Berezhiani’s Talk: MIRROR WORLD Lee and Yang, parity paper (1957) A bit more on N-N’ Oscillation:

27. What is a mirror neutron ? u’d’d’=n’ mirrror neutron

28. n-n’ oscillation Phenomenology: very similar to n-n-bar case:

29. Present status of search

30. 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 10 10 sec level will test for (B-L) (seesaw) scale < 10 11 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.

31. Discussion points: Physics issues- mass scale probed Cosmology Nuclear physics Experiment

32. Conclusion 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 >10 10 sec to test for  (B-L) (seesaw) scale less than 10 11 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.

33. B-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.

34. Nucleon Decay in Generic Signature Key test of GUTS: Gauge Boson mediated p-decay:

35. Origin 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.

36. Baryogenesis 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)