Tuesday, June 22, 2010

Could Latest Particle Finding Hint At Supersymmetry?

You may have heard the media throwing out headlines like the "God Particle" May Be Five Distinct Particles", referring to the latest findings that five Higgs Bosons may fit the data better than one.
In an experiment called DZero... Scientists recently found that collisions of protons and antiprotons produced pairs of matter particles more often than pairs of antimatter particles.   The difference... can't be explained by a standard model that assumes the existence of a single Higgs boson...
The DZero results can, however, be explained if scientists assume the Higgs boson is actually five particles...
Now, when I first heard these results I thought "What's really interesting here isn't that there may be 5 Higgs Bosons, but that this sounds an awful lot like supersymmetry." Luboš Motl agrees.  (Read his post for more details.)

Here's why this is interesting from the supersymmetry perspective: In the traditional non-supersymmetric standard model the Higgs Boson is a "doublet", meaning in semi-layman's terms it consists of two complex fields. (A double of the Lie Group SU(2) to be more precise.)  But each complex field can be decomposed into two fields representing the real and imaginary parts. (Just like the complex number z can be decomposed into numbers a and b such that z = a + ib.)

After symmetries are broken, three of the four fields go into giving the W+, W- and Z Bosons mass.  The single degree of freedom left over becomes the long sought after Higgs.

In supersymmetry you need the Higgs to really be two Higgs doublets to avoid anomalies. (Or in lay terms, to get the math to work out right.)  Therefore, there are 4+4 = 8 particles that after symmetry breaking become 8 - 3 = 5 particles.  Again, the 3 like the above were "eaten" to give the W+, W- and Z bosons mass.

So, data where five Higgs particles is a better fit isn't interesting because there may be five God particles, but because this could be hinting at supersymmetry!  However, before I count my chickens before they hatch, let me repeat the famous mantra: Half of all three sigma detections are false.  In other words, this five particle best fit may or may not be real.

This is the article: Bogdan A. Dobrescu, Patrick J. Fox, Adam Martin: CP violation in B_s mixing from heavy Higgs exchange, arXiv:1005.4238.


  1. Excellent mantra. I think I'll wait and believe in a supersymmetric Higgs mechanism when we've got some self-respecting evidence for it.

  2. Bryan,

    Thanks, unfortunately it is too often true.

  3. Awesome! I am new to the whole physics thing, but I do get the Lie Group part! I'm excited to see how this will unfold.

  4. I am a little worried that the state of theoretical physics is such that you can explain almost anything with whatever fundamental theory you want. (Just add more scalar fields until your favorite theory works. :))

    That said, and I get this from parameter fitting in cosmology, some models fit the data more *naturally* than others. Supersymmetry naturally fits a 5 particle Higgs model so this could be good news for supersymmetry lovers.

  5. "Just add more scalar fields until your favorite theory works."

    That sort of thinking happens in dynamo theory too. In an attempt to linearize the horribly non-linear world real dynamos live in, people work in so-called mean field theories that require an additional linear term with a free-parameter, traditionally called alpha, in front. However if you can't make it work with a scalar alpha, then people turn the scalar into a rank two tensor so you have nine free parameters instead of one.

    And let's be honest - with nine free parameters you can fit just about anything.


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