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STERILE NEUTRINOS

STERILE NEUTRINOS. The n MSM model. T. Asaka and M. Shaposhnikov Phys.Lett.B620(2005)17 M.Shaposhnokov Nucl.Phys.B763(2007)49 Minimum extension of the SM to accomodate massive neutrinos See-saw formula for active neutrinos m n =-M D (1/M I )(M D ) T Majorana mass M I

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STERILE NEUTRINOS

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  1. STERILE NEUTRINOS

  2. The nMSM model • T. Asaka and M. Shaposhnikov Phys.Lett.B620(2005)17 • M.Shaposhnokov Nucl.Phys.B763(2007)49 • Minimum extension of the SM to accomodate massive neutrinos • See-saw formula for active neutrinos mn=-MD(1/MI)(MD)T • Majorana mass MI • Dirac mass MD=fv v=174 GeV vac exp val of Higgs field • Usual choice: f as in quark sector, M = 1010-1015 GeV • Alternative choice: small f • Inputs: m(n1)= 10-5 eV, m(n2)= 9 meV, m(n3)= 50 meV and mixings

  3. Three sterile neutrinos • Three singlet RH neutrinos N1 N2 N3 •  N1 with very large lifetime, • Best choice : m(N1) 10 keV •  N2, N3 almost degenerate (leptogenesis) • With masses 100 MeV-few GeV

  4. Decay of a 10 keV neutrino N1 3 n, but also radiative decay • Almost stable DARK MATTER •  Warm dark matter

  5. Limits from cosmology Search for N1 radiative decays Big Bang nucleosynthesis, N2, N3 U2 < 10-8 (1/m(GeV))2

  6. Heavy neutrinos at accelerators • Mixed with active neutrinos • In all weak decays they appear at the level U2Nl Their mass is limited by the parent particle p e N m(N) < 130 MeV pm N m(N) < 20 MeV K  e N m(N) < 450 MeV K m N m(N) < 350 MeV

  7. Change in kinematics Helicity conservation revisited K  eN K mN

  8. Decays of heavy neutrinos Purely weak decays: modes depend on the N mass first open channel e+e-n, then men, m+m-n, e-p+, m-p+…. Lifetime for e+e-n t = 2.8 104 (1/m(MeV)5)(1/U2)

  9. PS191 experiment (1984!) 5 1018 pots 19 GeV

  10. « Typical » event

  11. PRESENT LIMITS

  12. Mixing to the nt • With the NOMAD experiment, 450 GeV p • Source Dst nt

  13. MiniBoone excess ? About 100 events depositing 300-400 MeV energy Obtained with 5 1020 pots of 8 GeV

  14. Possible interpretation Theoretical prejudice in the frame of nMSM model: Decay of the N2 component mixing predominantly to m (testing UNm2) 130 MeV < m < 350 MeV

  15. Guesstimates N produced in Kaon decays  Flux 3 1016 U2 Corrections due to kinematics x 3 And also from focalisation x 5 Decay probability : bgct(m) = 1013 E(MeV)/m6 U2 m = 150 MeV U2 = 10-7 m = 200 MeV U2 = 4 10-8 m = 250 MeV U2 = 2 10-8 NOT EXCLUDED !!

  16. Improving on PS191 • Modern n beam: NuMI (25 years later) • 120 GeV, 16 1020 pots • Large p, K production •  improvement in U2 limits • Furthermore, with D production mass range can be extended to 1.3 GeV

  17. NuMI beam • Flux de neutrinos arrivant sur le détecteur MINERvA

  18. (Parenthesis on the LHC) • LHCb • 1012 B mesons/year of 100 GeV/c Mass region extended to 4 GeV • ATLAS/CMS • 3 108 W/year Mass region extended to 50 GeV

  19. Rough expectations

  20. Conclusion • The nMSM is an appealing model • It is possible to test it rather simply in the NuMI beam. • An add-on decay volume in the near hall of NuMI could give valuable limits (or find sterile neutrinos!) • It could test the MiniBoone excess

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