STERILE NEUTRINOS

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STERILE NEUTRINOS

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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 - PowerPoint PPT Presentation

Transcript of STERILE NEUTRINOS

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STERILE NEUTRINOS

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The 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=-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(1)= 10-5 eV, m(2)= 9 meV, m(3)= 50 meV and mixings

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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

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Decay of a 10 keV neutrino

N1 3 , but also radiative decay

Almost stable DARK MATTER

• Warm dark matter

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Limits from cosmology

Search for N1 radiative decays

Big Bang nucleosynthesis, N2, N3

U2 < 10-8 (1/m(GeV))2

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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

e N m(N) < 130 MeV

N m(N) < 20 MeV

K e N m(N) < 450 MeV

K N m(N) < 350 MeV

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Change in kinematics

K eN K N

Helicity conservation revisited

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Decays of heavy neutrinos

Purely weak decays:

modes depend on the N mass

first open channel e+e-, then e, +-, e-+, - +….

Lifetime for e+e- 2.8 104 (1/m(MeV)5)(1/U2)

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PS191 experiment (1984!)

5 1018 pots 19 GeV

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« Typical » event

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PRESENT LIMITS

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Mixing to the

•With the NOMAD experiment, 450 GeV p

•Source Ds

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MiniBoone excess ?

About 100 events depositing 300-400 MeV energy

Obtained with 5 1020 pots of 8 GeV

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Possible interpretation

Theoretical prejudice in the frame of MSM model:

Decay of the N2 component mixing predominantly to (testing UN

2)

130 MeV < m < 350 MeV

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Guesstimates

N produced in Kaon decays

Flux 3 1016 U2

Corrections due to kinematics x 3

And also from focalisation x 5

Decay probability :

c(m) = 1013 E(MeV)/m6 U2

m = 150 MeV U2 = 10-7

m = 200 MeV U2 = 4 10-8

m = 250 MeV U2 = 2 10-8NOT EXCLUDED !!

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Improving on PS191

• Modern beam: NuMI (25 years later)

• 120 GeV, 16 1020 pots– Large , K production– improvement in U2 limits– Furthermore, with D production mass range

can be extended to 1.3 GeV

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NuMI beam

• Flux de neutrinos arrivant sur le détecteur MINERvA

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(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

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Rough expectations

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Conclusion

• The MSM 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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