Neutrinos can interact with gamma rays through their magnetic moment couplings.

Since neutrinos and gamma ray has no charge, there is no interaction between neutrinos with gamma ray at lowest order. However, neutrino being a fermion carries spin and thereby posses magnetic moment. Thus, they have tiny magnetic dipole interaction with gamma rays.

Depending upon the nature of neutrinos, there could be direct dipole moment interaction (with Dirac type of neutrinos) and transitional dipole moment interaction (Majorana nature of neutrinos).

Neutrinos can interact with gamma rays through their magnetic moment couplings.

Since neutrinos and gamma ray has no charge, there is no interaction between neutrinos with gamma ray at lowest order. However, neutrino being a fermion carries spin and thereby posses magnetic moment. Thus, they have tiny magnetic dipole interaction with gamma rays.

Depending upon the nature of neutrinos, there could be direct dipole moment interaction (with Dirac type of neutrinos) and transitional dipole moment interaction (Majorana nature of neutrinos).

All this is described by the Standard Model and is taught in particle physics courses. Gamma rays are photons whose frequency takes values in a certain range. Since neutrinos do not carry electric charge, they don't interact, directly, with photons. Neutrinos do carry weak charge-that's how they interact directly with other particles and, thus, with photons. For instance, there is an interaction between the electron, the electron neutrino and the W. The electron and the W are electrically charged, therefore, they can interact, directly, with photons and, this can give rise to an effective interaction between neutrinos and photons-which, of course, is very weak.

Neutrinos have no electric charge but carry weak charge. There three types of neutrinos, electron-neutrinos, mu-neutrinos and tau-neutrinos. An electron-neutrino, for example, can emit a virtual electron and a virtual W boson. They are called "virtual" because they do not have the mass of the real ones. The two, electron and W, live a very short time and soon recombine again in an electron-neutrino. Similarly for the other two neutrino types.  Both electron and W are electrically charged and do interact with photons.

Such interactions can give origin to a magnetic moment of the neutrino. To look at it, experimentally we perform an experiment of scattering of neutrinos on an electron target. The neutrinos, better antineutrinos, are those produced by a nuclear power reactor. We detect the scattered electron and measure its energy spectrum. We calculate the spectrum as expected for zero neutrino magnetic moment and search for deviations from that, especially at low, several keV, energies. No such deviation has been observed so far, allowing one to set an upper limit on the electron neutrino magnetic moment. The present one is

Of course the Standard Model ``works for neutrinos''-it correctly predicts their properties, that have been studied at CERN and elsewhere. It does *not* assume that the neutrinos are massless. For the issue discussed here the charged lepton-neutrino-W vertex is relevant, along with the fact that the charged leptons and the W interact with photons. The fascinating aspects of neutrinos that go beyond the Standard Model don't enter the picture here.

Stam,

it may be a matter of definition. As taught in the elementary particle physics courses the SM has three neutrinos that are left and have zero mass. If this is the definition of the SM, it clearly works for the experiments at accelerators on short baselines between production and detection. And works very well indeed. But over longer flight lengths it is in contradiction with the facts, because it does not foresee oscillations between falvours, which have been experimentally observed, and prove that neutrinos have non zero mass and, in addition, that flavour lepton numbers are not conserved.

The issue is relevant also here, because if, for example, neutrinos are Majorana particles the diagonal elements of the magnetic moment matrix are zero, with experimental consequences

I don't think that the definition given is in contradiction with the facts, since the seesaw mechanism can be implemented to describe the non-zero masses and the oscillations. Of course I agree that  the *numerical values*  imply that a mechanism ``beyond the Standard Model'' is needed to describe the hierarchy of values. I, also, agree that this is, somewhat, semantics. 

My point is that, within the Standard Model, it is possible to make a well-defined calculation regarding the interaction of the neutrinos it describes and the photons. Whether this calculation can be experimentally tested is, of course a matter that experimentalists are qualified to judge.

Yes, They can interact through magnetic coupling, which is so small since it can be acquired only at loop level.