Wednesday, July 04, 2012

Talking about Higgs

Lawrence Krauss has a reasonable article in Slate talking about the Higgs boson announcement.  He's quite chuffed, as you might expect:
The discovery announced today in Geneva represents a quantum leap (literally) in our understanding of nature at its fundamental scale, and the culmination of a half-century of dedicated work by tens of thousands of scientists using technology that has been invented for the task, and it should be celebrated on these accounts alone.
 His explanation of how it works uses a simple analogy:
 The idea of the Higgs particle was proposed nearly 50 years ago. (Incidentally, it has never been called the “God particle” by the physics community. That moniker has been picked up by the media, and I hope it goes away.) It was discussed almost as a curiosity, to get around some inconsistencies between predictions and theory at the time in particle physics, that if an otherwise invisible background field exists permeating empty space throughout the universe, then elementary particles can interact with this field. Even if they initially have no mass, they will encounter resistance to their motion through their interactions with this field, and they will slow down. They will then act like they have mass. It is like trying to push your car off the road if it has run out of gas. You and a friend can roll it along as long as it is on the road, but once it goes off and the wheels encounter mud, you and a whole gang of friends who may have been sitting in the back seat cannot get it moving. The car acts heavier.....

 All of the predictions based on these ideas have turned out to be in accord with experiment. But there was one major thing missing: What about the invisible field? How could we tell if it really exists? It turns out that in particle physics, for every field in nature, like the electromagnetic field, there must exist an elementary particle that can be produced if one has sufficient energy to create it. So, the background field, known as a Higgs field, must be associated with a Higgs particle.

But Bee Hossenfelder is feeling a bit glum already:
 And so, strangely, on this sunny day for high energy particle physics, I feel somewhat blue about the prospects. It's been almost two decades since the last discovery of a particle that we presently believe is elementary, the top quark in 1995, which was the year I finished high school. It's been a long way and an enormous effort to that little bump in the above plot. There isn't so much more we can do with hadron colliders. If we try really hard, we can ramp up the energy a little and improve the luminosity a little. Of course what we want next is a lepton collider like the ILC that will complete the picture that the LHC delivers.

But we have a diminishing return on investment. Not so surprisingly - it's the consequence of our increasingly better understanding that it takes more effort to find something new. And to make that effort of blue sky fundamental research, we need societies who can afford it. There's an economic question here, about the way mankind will develop, it's the question whether or not we'll be able to take care of our survival needs, and still continue to have enough resources to push the boundary of nature's secrets back further.

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