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Yuri Kamyshkov / University of Tennessee

International Workshop “Search for Baryon and Lepton Number Violations”, LBLN Berkeley, September 20-22. Search for B-L violation with neutrons at. Yuri Kamyshkov / University of Tennessee. Is (B –L) number conserved?.

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Yuri Kamyshkov / University of Tennessee

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  1. International Workshop “Search for Baryon and Lepton Number Violations”, LBLN Berkeley, September 20-22 Search for B-L violation with neutrons at Yuri Kamyshkov / University of Tennessee

  2. Is (B–L) number conserved?  In regular matter (B–L) = # protons + # neutrons – # electrons  0 (BL)  0 ; Is it a smoking gun?  In the Universe most of the leptons exist as, yet undetected, relict neutrino and antineutrino radiation (similar to CMBR) and the conservation of (B–L) on the scale of the whole Universe is still an open question  Fast anomalous SM interactions (sphalerons) in early Universe require that (BL) should be violated at > 10 TeV scale V. Kuzmin, V. Rubakov, M. Shaposhnikov, 1985 “Proton decay is not a prediction of baryogenesis!” [Yanagida’02] ↑ with conservation of (BL)

  3. (B–L) : two possibilities

  4. B = L e.g. n   or p  e+ (nucleon  lepton) most promising ! B = 0 ; L = 2    i.e. Majorana neutrino, 2 observable L = 0 ; B = 2 n  n oscillations Possible (BL)V manifestations following from (BL)=2 also e.g.   n +  or   + + (with heavy flavors involved) Why neutrons? nR is a singlet part of the SM and available for experiments while R might be very heavy and difficult to detect All observable (BL)=2 processes are topologically similar: operators of dim-9 for non-SUSY amplitude  There must be a scale of (BL) violation and physics

  5. |B|=2 ; |(BL)|=2 There are no laws of nature that would forbid the N  Nbartransitions 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 N  Nbar was first suggested as a possible mechanism for explanation of Baryon Asymmetry of Universeby V. Kuzmin, 1970 N  Nbarworks within GUT + SUSY ideas. First considered and developed within the framework of L/R symmetric Unification models by R. Mohapatra and R. Marshak, 1979 …

  6. Non-SUSY models Supersymmetric Seesaw for  BL , LR Plank scale Left-Right symmetric GUT SUSY GUT PDK nn nn Dutta-Mimura-Mohapatra (2005) Mohapatra & Marshak (1980) Scale improvement from new measurement Low QG models nn LHC Dvali & Gabadadze (1999)

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

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

  9. PDG 2006: Limits for both free reactor neutrons and neutrons bound inside nucleus New SK result today  Bound n: J. Chung et al., (Soudan II) Phys. Rev. D 66 (2002) 032004 > 7.21031 years Free n: M. Baldo-Ceolin et al.,  (ILL/Grenoble) Z. PhysC63 (1994) 409 with P = (t/free)2 (talk of A. Gal) Search with free neutrons is square more advantageous but with suppressed intra-nuclear transitions the larger number of neutrons can be available although with background limitations

  10. Previous N-Nbar search experiment with free neutrons At ILL/Grenoble reactor in 89-91 by Heidelberg-ILL-Padova-Pavia Collaboration M.Baldo-Ceolin M. et al., Z. Phys., C63 (1994) 409 No background! No candidates observed. Measured limit for a year of running:

  11. How one can improve on such state-of-the-art experiment and achieve 3-4 orders of magnitude higher sensitivity? • Two major possible improvements: • Focusing of neutrons: use of larger solid angle •  longer neutron flight path  1 km • 2. Vertical layout: compensating Earth gravity

  12. Homestake shafts Yates Ross #5; 5137

  13. N-Nbar search experiment idea with vertical layout 105 Pa Neutron source needed: commercial TRIGA type small power 3.4 MW reactor Not to scale

  14. February 9, 2006, Lead, SD (LOI #7) Search for neutron  antineutron transitions at DUSEL N-Nbar proto-collaboration Goal is to build a vertical 1-km long experiment with zero background that would be factor of 1000 more sensitive than previous expt. at ILL/Grenoble

  15. TRIGA Very Cold Vertical Beam, 3 years TRIGA Cold Vertical Beam, 3 years Super-K’07 Cold Beam

  16. Spare slides

  17. calculated by Ken Ganezer

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