17th Dec. 2011 ::
The Large Hadron Collider at CERN was designed with the Higgs Boson in mind. The reason for this was that scientist have known for a long time that discovery of the Higgs particle would change our understanding of the universe forever.
News this week seems to indicate that we may have taken a major step towards making that change in our understanding of physics. Exactly the type of news that fascinates me and that I love to wonder about...
The Higgs particle was proposed by Peter Higgs way back in 1962, just after the first proposal of a "standard model" (in 1960) that attempted to explain the sub-atomic quantum world. As the Standard Model of physics has evolved into an incredible explanatory tool the open slot in the theory that exists for the Higgs has remained unfilled by experimental evidence. The Standard Model in fact, has evolved so far that the Higgs (or the "hole" that exists for it) is the last to be filled. The Higgs (and anything that comes with it) will be the final component in the model.
Even though the Standard Model is the best description we have of the subatomic world, it does not explain the complete picture. The theory incorporates only three out of the four fundamental forces - omitting gravity. There are also important questions it cannot yet answer, such as what is dark matter? and what happened to the missing antimatter that should account for 50% of the universe? However, the door to answers to these questions may just have been pushed ajar!
CERN - Image from GridPP
We now have fascinating news of a tantalising glimpse or the ultra-shy Higgs Particle.
Both of the main detectors at CERN; ATLAS & CMS have uncovered evidence for it's existence. This evidence narrows the "location" of its existence to around 125 gigaelectronvolts (GeV) making it a lightweight particle. This means that will (almost certainly) need additional particles to complete the picture and aid the Higgs in it's important role giving matter (the specific type of energy that appears solid to us) mass. These additional particles could be highly relevant...
Perhaps surprisingly scientist at CERN don't ever expect to "see" the Higgs directly - even once they have claimed it's discovery. The Higgs particle decays so quickly that even the LHC only detects remnants of it in the aftermath of particle collisions. Essentially this means an that scientists are looking for a excess of "remnant" particles in any particular collision with which to directly infer the Higgs and it's properties. Both CMS & ATLAS have seen this excess of remnant particles in the 125 GeV range. The statistical relevance of these observations is around 2.0 sigma (1 in 50) chance of random mathematical fluctuation. The discovery won't be claimed until this relevance is down to 5.0 sigma (1 in 1 million) chance of random fluctuation. (5.0 sigma is about the same level of chance as 20 people all tossing a coin each, and every one coming down heads - I love that image!)
Scientists seem to be quite delighted with this progress and what looks like the the weight of the Higgs. Part of this enthusiasm is the space that it leaves for additional particles. Is this the key - the clue - for further physics beyond the standard model? Is this the doorway to Supersymmetry (SUSY)? Will this explain dark matter? Are there two types Higgs particle? One that connects matter to the Higgs field and one that connects Dark Matter to it's equivalent field? Will there be a non-standard model of Dark Matter physics?
If this really is the Higgs Particle that the CERN scientists are looking at, 2012 should be the year in which its discovery is formerly announced - and what an achievement that will be! After that, it seems that CERN will have opened a new door on the universe and have lined up a lot more discovering yet to come...
Discussions at Perimeter Institute for Theoretical Physics, Ontario, Canada.