Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Nuclear stability and variations of SM params

  1. Nov 6, 2012 #1
    I am looking at this pretty chart:


    My question is, how sensitive is it to the variation of SM parameters?
    Imagine that I am sitting in front of some magic TV, where the image above is displayed. Below there are sliders, one per SM parameter. I start to move these sliders, looking at the screen.

    So how sensitive is function of nuclear stability to the small variation of parameters, how much do I need to change to start seeing any difference or to completely change they way how it looks?

    Of course there are no exact answers, but any rough estimations - like 1%, 0.01%, or 0.00000001%?
  2. jcsd
  3. Nov 7, 2012 #2


    User Avatar
    2017 Award

    Staff: Mentor

    You can extract the general shape of that diagram with the mass formula. The coefficients depend on fundamental parameters - not strictly linear, but at least something similar.

    If you increase the fine-structure constant by 1%, the coulomb term will increase by 2%, and large nuclei need a few neutrons more to be stable (similar to 2%, I would guess, which corresponds to ~3-5 neutrons).

    If you increase the strong force by 1%, volume and surface term will change in a similar way, and I would expect that more (heavier) nuclei become stable or long-living.

    If you change the up- or down-quark masses, the ratio protons/neutrons will change a bit.

    If you change the strength of the weak interaction or the W boson mass, you change the half-life of beta decays. That influence is certainly nonlinear.

    Other constants: Hmm...

    Cosmology can be more sensitive to some changes - if neutrons would be >0.5 MeV lighter than protons for example, protons would decay to stable neutrons, and stars (if they would exist at all) would look completely different. The Triple-alpha_process is quite sensitive to energy states, too.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook