STERILE NEUTRINOSand other exotica

Neutrino physicsOfficial do-it list

13 ?

Improve 12 , 23

Mass hierarchy

Improve m1, m2, m3

Dirac or Majorana

CP violation

astronomy

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

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

Decay of a 10 keV neutrino

N1 3 , but also radiative decay

Almost stable DARK MATTER

• Warm dark matter

Limits from cosmology

Search for N1 radiative decays

Big Bang nucleosynthesis limits for N2, N3

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

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 particles

e N m(N) < 130 MeV

N m(N) < 20 MeV

K e N m(N) < 450 MeV

K N m(N) < 350 MeV

… W e N m(N) < 80 GeV

Change in kinematics

K eN K N

Helicity conservation revisited

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)

PS191 experiment (1984!)

5 1018 pots 19 GeV

« Typical » event

PRESENT LIMITS

Mixing to the

•With the NOMAD experiment, 450 GeV p

•Source Ds

MiniBoone excess ?

About 100 events depositing 300-400 MeV energy

Obtained with 5 1020 pots of 8 GeV

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

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 !!

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

NuMI beam

• neutrino flux on the MINERvA detector

(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

U2

10-6

10-7

10-8

10-9

10-10

0 0.1 0.2 0.3 0.4 GeV 0 0.5 1.0 GeV 0 10 20 30 40 GeV

Minera Minera

Rough expectations

K±

D±

LHC

B W±

E.M. interactions of neutrinos

1) Magnetic moment

2) Radiative decays

3) Stimulated conversion

2 1W

l

Radiative decaysTheory:

GIM suppressed = 7 1043 1/m5 1/U2 (s)

Experiment:

1) Mass hierarchy E = E/2

SN anti-e /m > 6 1015 s/eV

Los Alamos /m > 15,4 s/eV

2) Degenerated masses E = E m2/m2 = 2 E m/m

Bugey anti-e /m > 2 10-4 s/eV if m/m > 10-7

Solar eclipse /m > 100 s/eV if m2 ~ 10-5 eV2

Matter enhancement

Coherent interactions on atomic electrons

e

2

W1

e

0/m ~ 3 1024 (Ne/1024)2 (m/E) (1eV/m)4

dE/dx by neutrinosWe exposed a HP Ge crystal (140 cm3) to a beam

- First, in the HE (24 GeV) CERN beamContinuous current increase above leakage current during spills (4

pA) proportional to the beam intensity

< 10-5 eV/cm for (10-12 of mip)

< 10-3 eV/cm for e

This translates into radiative lifetime limits

/m > 10-16 E s/eV for 5 10-11 < m/m < 2 10-8

In vacuum equivalent to 0 > 1019/E/m2 (s)

dE/dx by neutrinos, cont.

Then, at the Bugey reactor

1 hour exposure, beam off!

e beam (e /anti-e = 2 10-4 from 55Fe and 51Cr)

Looking for e ’ + (explanation of solar deficit)

Result: /m > 3 10-4 s/eV

Equivalent to: 0 > 9 1015 s

Stimulated conversion in RF cavity

Another possibility to overcome GIM suppression M.C Gonzalès-Garcia, F. Vannucci and J. Castromonte Phys.Lett. B373,153(1996)

Idea: RF cavity is a bath of photons (1026 of 10-6 eV) On-off method

Majorana neutrinos anti-e or anti-

Dirac neutrinos sterile

R = N/N = (Q/109)(P/100W)(m/eV)3(eV2/m2)3(s/)

0 = 20/R (m/m2)3

If R<10-2 0 > 4 1015 s for m2 = 8 10-5 eV2 and m = 1 eV

If a signal were to be found, possibility to measure absolute masses and CP effects

Conclusion

• Sterile neutrinos:• The MSM is an appealing model• It is possible to test it simply in the NuMI beam

and beyond.

• EM interactions of neutrinos:• Large improvements possible, with a very small

effort.