Tuesday, May 21, 2013

Gran Sasso, Solar Neutrinos, and Radioactive Decay Rates

We interrupt your normal coverage of magnetic monopole searches today to bring you something much more cool from well.. the same location!  I was jazzed to find out yesterday that the next monopole project I was going to write about was done at a stunningly pretty location Gran Sasso, Italy. (picture 1)


Then, thanks to +Oliver Thewalt I found out about a very interesting study done regarding a possible time dependence of the decay rates of radioactive isotopes.  So much for the pretty location I thought, but the science is incredibly interesting.  Then, while reading up on the research this morning I found out that one of the studies[2] was performed at none other than the very same lab in Gran Sasso.  And we're back to where we started and I get to include a pretty picture with the post!  OK, OK enough with the cool coincidences and the small world of science for today.

So, here's what's going on in a nutshell.  Radioactive elements decay in a random fashion, but at a very well defined rate.  In other words, you never know exactly when the next individual atom of the material will decay, but you do know with great certainty how long it will take for half of the material to decay.  For example, the carbon dating process is based on the certainty of the half life of carbon 14[5].  Until recently, the rate of decay was thought to be a constant.  Then, a researcher at Purdue University, Ephraim Fischbach, noticed what looked like a periodic variation in the decay rate of radioactive materials over the course of months and sometimes years.  Additional research revealed that there might be a correlation between this measured variation and the neutrino output from the sun.  For a great summary of the research check out the Stanford backgrounder on the subject [3].  The graph shown in picture 2 is from Fischbach's paper.  It shows the variation in the decay rate of radium 226 with time and correlates the decay rate variation with the variation of the distance between the Earth and the Sun, (shown as a solid line)[6][7].



Gran Sasso
You thought I forgot about Gran Sasso didn't you?  They performed an experiment which they believe refutes the relationship found by Fischbach et al.  Here's a quote from the conclusion of their paper[2][2a]


"...in clear contradiction with previous experimental results and their interpretation as indication of a novel field (or particle) from the Sun..."

The experiment was done at Gran Sasso because conditions there were great.  The laboratory is actually located underground, (under a lot of ground), and well protected from variations in both electromagnetic fields and temperatures (picture 3).


The results are still up in the air.  The Fischbach group responded to the Gran Sasso paper[8], and Fischbach believed in the results enough to file for a patent on a solar event detector based on the results in 2008[4], (picture 4).



There will be much more on all this to follow.

Reference:
1.  The latest and greatest from Jenkins, Fischbach, et al. (open access)
http://arxiv.org/abs/1211.2138

2.  The Gran Sasso null result
http://dx.doi.org/10.1016%2Fj.physletb.2012.02.083
Bellotti E., Broggini C., Di Carlo G., Laubenstein M. & Menegazzo R. (2012). Search for time dependence of the 137Cs decay constant, Physics Letters B, 710 (1) 114-117. DOI:

2.a.  The Gran Sasso paper in open access
http://arxiv.org/abs/1202.3662

3.  Stanford sums it up
http://news.stanford.edu/news/2010/august/sun-082310.html

4.  Fischbach's patent
http://www.google.com/patents?id=WTy_AAAAEBAJ&zoom=4&dq=decay%20%22E%20Fischbach%22&pg=PA1#v=onepage&q&f=false

5.  Carbon dating on Wikipedia
http://en.wikipedia.org/wiki/Radiocarbon_dating

6.  Fischbach et al.'s first paper from 2008 (open access)
http://arxiv.org/abs/0808.3283

7.  The same paper in the journals
http://dx.doi.org/10.1016%2Fj.astropartphys.2009.05.004
Jenkins J.H., Fischbach E., Buncher J.B., Gruenwald J.T., Krause D.E. & Mattes J.J. (2009). Evidence of correlations between nuclear decay rates and Earth–Sun distance, Astroparticle Physics, 32 (1) 42-46. DOI:

8.  Response to the Gran Sasso paper (open access)
http://arxiv.org/abs/1211.2138


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