It can be minimal, while also unconstrained, split and violated. ‘It’ is, of course, SUSY.
I was flicking through some of the talks in the schedule of the SUSY 09 conference being held
in Boston, Ma this week, and learning a number of interesting things along the way. In my opinion ‘learning
interesting things’ is a good thing to get from any conference and can fuel your own imagination
for future work. So it was in this state of learning I studied the slides covering a vast spectrum of
potential ways to hint at, or direct methods to discover, supersymmetry.
It reminded me of a story from a workshop I attended when I was a young, wet-behind-the-ears graduate student. Two distinguished gentlemen physicists were in the queue for coffee/beer/snacks or whatever it was, and were regaling stories of a recent meeting. One mentioned to the other about a mutual friend who he had happened to catch taking a cheeky nap during a talk on Supersymmetry. He then made his colleague enter into a fit of laughter when he continued that their friend was jolted awake by the speaker mentioning, at some point during the talk, that he was “violating SUSY”. The two senior scientist giggled like schoolboys at this and mused as to whether their colleague had “a past history with SUSY”, or had, “violated SUSY himself perhaps” and other such comments. It struck me at the time as a little childish, but the moment had a silly charm, in the same way any giggling pensioner does.
Fast forward a few years and SUSY is no laughing matter. It is the shining beacon of new physics discovery in the near future and the raison d’etre of the LHC physics program, along with ‘the Higgs thing’. SUSY is considered an eventuality, no longer an exotic possibility, the conundrum being how it will be discovered, not if. Supersymmetry does present a rich and elegant new physics tapestry by which many problems that we have with the current Standard Model can be neatly solved. To date, there is no hard evidence of the existence of any suspersymmetric particles. The lightest SUSY particle, since it need not decay, would provide a tempting, and in some theories quite elegant, solution to Dark Matter by being the candidate particle that makes up this large fraction of the matter of the Universe. But this can often be brought forth in an ad hoc let’s-kill-two-birds-with-one-stone type of way. What I find most interesting as an experimentalist is that although SUSY has yet to be observed it is treated in a very different way to other potential new physics phenomena. In particular, people EXPECT SUSY to show up at the LHC. The “I told you so’s” will have to wait for the data to see whether this is the case.
Allow me to take a momentary aside at this point to bring those of you up to speed who have diligently read this far without the slightest notion of what it is I speak. SUSY is the abbreviated name for Supersymmetry, that provides a relation between elementary particles of one spin to another particle whose spin differs by half a unit; these are known as ‘superpartners’. In basic terms therefore, in a supersymmetric theory, for every type of fermion (like an electron from example) there exists a corresponding type of superpartner boson (selectron), and vice-versa. As the astute among you will have gathered this leads to roughly doubling the number of (fundamental) elementary particles, great news for experimentalists as it gives us all kinds of new things to look for.
If (some would say when) supersymmetry is discovered it will be a major achievement for high energy physics and usher in a whole new era of measurements that will profoundly alter the ways in which we view the Universe and the spectrum of it’s constituent fundamental particles. On the other hand, should we manage to rule out some regions of the SUSY parameter space (we can’t completely rule out SUSY as a possibility but can say that certain aspects of it are very unlikely) this could point to a completely different way, perhaps not yet considered, in which the various things SUSY provides can be manifested without recourse to doubling the particle count.
For those eager to learn more, an excellent source of information about the subject can be found in Stephen Martin’s ‘Primer’ on the subject here.