ELECTROMAGNETIC INTERACTIONS OF

NEUTRINOS IN MATTER

Int. School of Nuclear PhysicsProbing hadron structure with lepton & hadron beams

E.M. interactions of neutrinos

1) Radiative decays

2) Magnetic moment

3) Stimulated conversion … all GIM suppressed in

vacuum!

2 1W

l

Present limits

Radiative decaysSM theory: 0 = 7 1043 (1eV/m)5 (s) Pal & Wolfenstein (1982)

Experiments: SN1987 (strong MH): /m > 6 1015 s/eV Bugey (mass degenerated): m > 310-4 s/eV if m/m >10-7

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

Magnetic momentSM theory: = 3.2 10-19 m(eV) B

Experiment (solar): < 0.54 10-10 B

Amplification in matter

Coherent interactions on the atomic electrons

e

2

W

1

e

0/m ~ 9 1023 F(v)(Ne/1024cm-3)2 (1eV/m)4

If mass-degenerated

0/m ~ 9 1023 F(v)(Ne/1024cm-3)2 (1eV/m)4 (m2/m2)2

J.C.d’Olivo, J.F.Nieves (1989), G.Giunti et al. (1991)

Neutrino energy deposition in a Ge crystal

Neutrino beam

High purity Ge diode 140 cm3 at liquid nitrogen temperature (77K)Electron-hole pair creation work 3 eV: very low

energy thresholdEnergy resolution ~ keV

Integral search: the principleA.Castera et al., Phys.Lett.B452, 150

High intensity beam: 20 GeV 1013 pot in 4 ms spills, every 14 s

1 mip (muon) gives a sudden signal~ 30 MeV in 5 cm

Search: Continuous energy deposition building up during the spill duration

Results

Clear on-beam signal of crossing mip’s

No excess of deposited energy < 3 keV in 5 cm

Analysis8 107 and anti- per spill crossing the crystal

Total energy deposition < 3 keV in 5 cm of Ge

< 10-5 eV /cm: 10-12 normal dE/dx< 10 keV for whole earth diameter~ 10-2 eV /cm for weak interactions

Case of mass-degenerated radiative decayE = E m2/m2 = E 2m/m 2 eV < E < 200

eV10-10 < m/m < 10-8

Prob < 10-5/E m > 5/3 10-5 m2/m0 > 1.5 1018 m3/m2

An encore at the Bugey reactor

Powerful source of anti-e: ~ 1021/sBut also e from activation of the container: 55Fe produces a peak at 230 keV and 51Cr peak at 750 keV15 m from the core: 4 109 /cm2 for each of the 2 peaks

m/m > 3 10-4 s/eV in Geequivalent to

/m > 9 1015 s/eV in vacuum

Stimulated conversion in an RF cavityAnother way to amplify EM interactions M.C Gonzalès-Garcia, F. Vannucci and J. Castromonte Phys.Lett. B373,153(1996)

Idea: an RF cavity is a photon bath (100W 109 QF~1023 cm3 à 10-6 eV)

Majorana neutrinos anti-e ou 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 > 2 1018s for m2=10-5 eV2 and m=1 eV

But also + +

Recent development: sterile neutrinos

What are sterile neutrinos?-Do not participate in Weak Interactions-Couple to the “real world” through mixing

(e, , , H …) = [U] (1, 2, 3, 4 …)

Bad reasons: try to explain anomalies in past neutrino dataLSND, MiniBoone, nuclear reactors, radioactive sources

Good reasons: neutrinos are massive, need of Right Handed componentsClassical see-saw model, very high masses, but variations exist

Every neutrino flux has some H component at the level of UHl2

Example: the MSM modelThree sterile neutrinos, one of them having ~10 keV/c2 mass

Almost stable DARK MATTER

• Warm Dark Matter

7 1043 (1eV/m)5(1/U2) (s)

Cosmological limits

Search of monoenergetic photons

Sterile neutrinos as WDMm(H) ~ 7 keVU2 ~ 10-10

In vacuum:0 = 4 1034 sIn matter:m ~1026 s

Local Dark Matter density: 300 MeV/cm3

Relative velocity: 200 km/sFlux of H on earth: 8 1011 H/cm2s (yearly modulation)

In crystal 1x1x1 m3: 10-8 decay/year !!… 5 10-4/year in SK, 10/year in IceCube

Conclusion

EM neutrino interactions exist in the Standard Model-Recent claim in astrophysics of radiative decay

indication?

They are hugely amplified in matter

… but not yet enough to consider an experiment in the labUnless nuclear physics help?