Strange modulation of radioactive decay rates with solar activity

Question

Recently I found out this strange article about nuclear decay rates somehow showing seasonal variations with a high correlation with sun activity.

1. Has this been experimentally confirmed/disproved? An experiment using neutrinos from a fission reactor would be awesome, although probably a couple orders of magnitude below the required luminosity (at least to be comparable with solar sources)

2. Could the standard model possibly allow neutrinos to modulate decay rates in this way? Or do we need new physics?

Link to the public version of the paper.

Another paper about this, but now the SuperKamiokande data is compared with data from Brookhaven: http://arxiv.org/abs/1301.3754 They also propose a model of the effect called neutrino "resonant spin-flavor precession".

Answer 1

Half life variations have been suspected for decades, and almost all (maybe all…but I do not pretend to have a comprehensive knowledge) have been shown to be caused by limits in experimental design. This latest set from this (now expanded) group (they did another paper on this topic a couple of years ago http://arxiv.org/PS_cache/arxiv/pdf/0808/0808.3283v1.pdf) is interesting. Any periodic variation in decay rates is of great importance regardless of whether it correlates to some astronomical phenomenon.

I guess that is a good setup for a “I’m not really going to answer your question, but” type answer.

The 2008 paper was followed by a set of measurements from the Cassini probe (http://arxiv.org/PS_cache/arxiv/pdf/0809/0809.4248v1.pdf). The distance between that probe and the sun was such that any sun effect should have been magnified. None was seen. This may disprove the solar effect, or it could say something about the isotopes used. The Cassini isotopes were different than the Purdue group’s isotopes.

The isotopes they used in the paper you cite were interesting: Mn 56: 2.6 hr, Si 32: 101 yr, Ra 226: 1,600 yr. From a quick scan of the plots it looks like the longer the half-life the greater the adherence to the annual periodicity. I also notice that the bulk of the data was accumulated before 1990, and the data after 1996 does not show the same adherence to the annual periodicity.

I’m trying not to discount these decay-rate observations, and there are good reasons to not discard them out-of-hand. Most observations of constant decay rates have been made with rapidly decaying isotopes over a short time frame. The experiments are just much easier to set up. Very long term experiments are relatively rare, and could illuminate previously unobserved phenomena. If the periodicity is on the order of a year it should only take a couple of years to confirm the data using available methodologies.

Answer 2

A quite detailed article (in german though) discussing this "effect" can be found here:

• Radioaktivität: Wer hat an der Uhr gedreht?

At the end of the article there is a list of interesting related papers and literature. According to this article first experiments trying to use artificially produced neutrinos to influence the decay rates of radioactive materials came out with negative results. So if the sun should influence the decay rate, it doesn't seem to be via neutrinos, but must be by some mysterious unknown force or particle. However most physicist seem to believe more in a systematic error produced by the used measurement equipment as explanation for this "effect".

Answer 3

I follow the work of Cahill (out of mainstream) about the The anisotropy of the speed of light. Although I think that we have no chance of measure this directlly I think that this effect can be an indirect manifestation of it. The path of Earth thru CMB referential is cyclic (annual). May be he is not far from a good viewpoint when he tried to model the flyby anomaly (Resolving Spacecraft Earth-Flyby Anomalies with Measured Light Speed Anisotropy - Cahill, Progress in physics 3, 9, (2008)) (*)
Of course I'm not absolutelly sure that this is the correct answer that, in the future, will be adopted. Anyway I keep myself vigilant with crazy ideas.

EDIT add :
The answer to this question may turn interesting:
The seasonal data as measured in this paper are better aligned with the direction of the dipole of the CMB (anisotropy of the speed of light) or the major axis of the trajectory of the Earth around the Sun (neutrinos) ?
I didnt found a graph of a seasonal variation of the projection (dot product) of the Earth's speed vector with the CMB dipole direction vector to compare with the graphs of this paper. I hope that someone can help with this.

Also from WP-CMBR_dipole_anisotropy:
The dipole anisotropy and others due to Earth's annual motion relative to the Sun... moving at 627±22 km/s relative to the reference frame of the CMB (also called the CMB rest frame, or the frame of reference in which there is no motion through the CMB) in the direction of galactic longitude l = 276±3°, b = 30±3°.
Some observers have pointed out that the anisotropies in the WMAP data did not appear to be consistent with the big bang picture. In particular, the quadrupole and octupole (l=3) modes appear to have an unexplained alignment with each other and with the ecliptic plane, an alignment sometimes referred to as the axis of evil. A number of groups have suggested that this could be the signature of new physics.

If I'm reading ok the ecliptic plane reads: the trajectory of Earth thru space.

As a comment: I've in my mind some form of why the anisotropy of the speed of light is important at nuclear scale but that is more than we need to discuss here.
The neutrino was the first darkness to enter in the menu and it will be the last to evade. Of course that nobody will take this statement seriously. I bet 100 % that the correlation to the CMB dipole direction is much more interesting than the neutrino link.

(*) I found a wild comment in the net that someone bet, and won, that the flyby RosetaIII (Nov/13/2009) will have a null result just because of the calendar date. Coincidence?