1. 4-th SNOLAB Workshop, August 15-17, 2005 at Sudbury Yuri Kamyshkov Univ. of Tennessee kamyshkov@utk.edu TRIGA reactor

2. We know: neutral matter oscillates strangeness beauty lepton flavor lepton number ? |  L|=2 baryon number |  B|=2 There are no laws of nature that would forbid the transitions except the conservation of "baryon charge (number)": M. Gell-Mann and A. Pais, Phys. Rev. 97 (1955) 1387 L. Okun, Weak Interaction of Elementary Particles, Moscow, 1963

3. 2003, M. Shiozawa 28th International Cosmic Ray Conference Prize the work of Super-K, Soudan-2, IMB3, Kamiokande, Fréjus All modes: baryon  anti-lepton conserving (B  L); searching for GUT and SUSY modes conserving (B  L)

4. Unification of Forces and SUSY To confirm SUSY and GUT ideas one should either discover super-symmetric particles or observe the proton decay. Although very attractive theoretically and supporting each other, so far these ideas are not confirmed experimentally ! GUT + SUSY

5. Important Theoretical Discoveries within Standard Model Anomalous nonperturbative effects in the Standard Model lead to violation of lepton and baryon number (’t Hooft, 1976) Anomalous nonperturbative effects in the Standard Model lead to violation of lepton and baryon number (’t Hooft, 1976) this B and L nonconservation in SM is too small to be experimentally observable at low temperatures, but it is large at T above electroweak scale. “On anomalous electroweak baryon-number non-conservation in the early universe” (Kuzmin, Rubakov, Shaposhnikov, 1985) “On anomalous electroweak baryon-number non-conservation in the early universe” (Kuzmin, Rubakov, Shaposhnikov, 1985) The anomalous SM interaction conserves (B  L) but violate (B+L). Rate of anomalous (B+L)-violating electroweak processes at T > TeV (sphaleron mechanism) exceeds the Universe expansion rate. If B = L would be set at very high temperature (e.g. at GUT scale) due to some (B  L) conserving interaction (e.g. by SU(5) SUSY proton decay), all quarks and leptons in the universe will be wiped out by (B+L) -violating electroweak processes. Baryogenesis can not be explained by (B  L) conservation.

6. N-nbar works within GUT + SUSY. First considered and developed within the framework of Unification models ( R. Mohapatra and R. Marshak, 1979). N-nbar works within GUT + SUSY. First considered and developed within the framework of Unification models ( R. Mohapatra and R. Marshak, 1979). N-nbar was first suggested as a possible mechanism for explanation N-nbar was first suggested as a possible mechanism for explanation of BAU (Baryon Asymmetry of Universe ) of BAU (Baryon Asymmetry of Universe ) V. Kuzmin, 1970 The observed Baryon Asymmetry of the Universe ( The observed Baryon Asymmetry of the Universe ( A. Sakharov,1967) tells us that Baryon number is not conserved, not GUT + SUSY “The proton decay is not a prediction of the baryogenesis” ( Yanagida @ 2002) “The proton decay is not a prediction of the baryogenesis” ( Yanagida @ 2002) If conventional (B  L)-conserving proton decay would be discovered If conventional (B  L)-conserving proton decay would be discovered e.g. by Super-K, it will not help us to understand BAU. (B  L) should be violated in Nature e.g. (B  L) should be violated in Nature e.g. In our laboratory samples: (#p + #n  #e)= (B  L) is violated. In our laboratory samples: (#p + #n  #e)= (B  L) is violated.

8. Some  (B  L)  0 nucleon decay modes (PDG’04) (B  L)  0 modes Limit at 90% CLS/BExperiment’year >1.7  10 31 yr 152/153.7IMB’99 >2.1  10 31 yr 7/11.23Fréjus’91 >2.57  10 32 yr 5/7.5IMB’99 >7.9  10 31 yr 100/145IMB’99 >1.9  10 29 yr 686.8/656SNO’04 >7.2  10 31 yr 4/4.5Soudan-II’02 > 4.9  10 25 yr Borexino’03 with free neutrons in vacuum has highest future reach in (B–L)  0 search

9. Bound n: J. Chung et al., (Soudan II) Phys. Rev. D 66 (2002) 032004 > 7.2  10 31 years  PDG 2004: Limits for both free reactor neutrons and neutrons bound inside nucleus Free n: M. Baldo-Ceolin et al.,  (ILL/Grenoble) Z. Phys C63 (1994) 409 with P = (t/  free ) 2 R is “nuclear suppression factor” Uncertainty of R from nuclear models is ~ factor of 2 models is ~ factor of 2 Search with free neutrons is square more efficient than with bound neutrons

10. n  nbar transition probability  -mixing amplitude All beyond the SM physics is here

11. n  nbar transition probability (for given  )

12. At ILL/Grenoble reactor in 89-91 by Heidelberg-ILL-Padova-Pavia Collaboration M.Baldo-Ceolin M. et al., Z. Phys., C63 (1994) 409 Previous n-nbar search experiment with free neutrons

13. Detector of Heidelberg -ILL-Padova-Pavia Experiment @ILL 1991   No background! No candidates observed. Measured limit for a year of running: = 1 unit of sensitivity

14. Scheme of N-Nbar search experiment with vertical layout  Dedicated small-power research reactor with cold neutron moderator  V n ~ 1000 m/s  Vertical shaft ~1000 m deep with diameter >5 m  Large vacuum tube, focusing reflector, Earth magnetic field compensation system < 3 nT  Detector (similar to ILL N-Nbar detector) at the bottom of the shaft (no new technologies)  No background: one event  discovery. Not to scale

15. Annular core TRIGA reactor (GA) for N-Nbar search experiment Economic solution for n-nbar: annular core TRIGA reactor 3.4 MW with convective cooling, vertical channel, and large cold LD 2 moderator (T n ~ 35K). Unperturbed thermal flux in the vertical channel ~ 2  10 13 n/cm 2 /s Courtesy of W. Whittemore (General Atomics) ~ 1 ft GA built ~ 70 TRIGA reactors 0.01  14 MW (th) 19 TRIGA reactors are presently operating in US (last commissioned in 1992) 25 TRIGA reactors operating abroad (last commissioned in 2005) some have annular core and vertical channel most steady, some can be pulsed up to 22 GW safe ~ 20% EU uranium-zirconium hydride fuel

16. New development enhancing n-nbar search sensitivity Very Cold Neutron Source with T n ~ 2.2K (IPNS/ANL R&D project by J.M. Carpenter et al., 2005) J.M. Carpenter et al., 2005 2.2K Maxwellian

17. Soudan-II limit  ILL/Grenoble limit = 1 unit of sensitivity

18. TRIGA Cold Vertical Beam, 3 years Cold Beam TRIGA Very Cold Vertical Beam, 3 years

19. Science impact of n-nbar search If discovered: n  nbar will establish a new force of nature and a new phenomenon leading to the physics at the energy scale of ~ 10 5 GeV will provide an essential contribution to the understanding of BAU might be the first detected manifestation of extra dimensions and low QG scale new symmetry principles can be experimentally established:  (B  L)  0 If NOT discovered: within the reach of improved experimental sensitivity will set a new limit on the stability of matter exceeding sensitivity of X-large nucleon decay experiments wide class of SUSY-based models will be removed (K. Babu and R. Mohapatra, 2001) further experiments with free neutrons will allow high-sensitivity testing (L. Okun et al, 1984) (S. Lamoreaux et al, 1991)

20.  Vertical shaft ~ 1 km deep, with dia  5 m to be instrumented  Construction access from the top and the bottom of the shaft  Site isolated from the main underground lab  Heat removal of 3.5 MW TRIGA reactor (at the surface)  Cryogen equipment for cold moderator (at the surface)  Many other things (too early to discuss) What is required for experiment at SNOLAB?

21. Vertical shafts and Lab infrastructure exists Vertical shafts and Lab infrastructure exists International scientific community exists International scientific community exists (Program Advisory Committee, reviews, etc) (Program Advisory Committee, reviews, etc) It might be possible to license a new reactor It might be possible to license a new reactor in Canada in Canada Why at SNOLAB ?