Could the Higgs boson have been discovered by accident? | The Knowledge Dynasty

Could the Higgs boson have been discovered by accident?

A theorist says no. I say yes. See what you think.

We have a tendency to oversimplify complicated issues. Sometimes this gives useful clarity, but more frequently it gives a distorted impression of what I am stubborn enough to call the truth. Clarity can be seductive, but is disastrously misleading if it neglects important facts. This is true in politics, in history, and in science.

In a recent article on how we came to discover the Higgs boson, my colleague, theoretical physicist James Wells, puts it like this:

A terse and deleteriously incomplete history of the Higgs boson says that it was postulated in 1964 by the theorist Peter Higgs and then discovered in 2012 by experimentalists after a multi-decade herculean construction project at CERN to find it.

This is, he says, a distortion of how science progresses, and of what enables scientific discoveries.

The Higgs boson was the last particle of the Standard Model of physics to be discovered. It occupies a unique and essential place in that theory, and its discovery validated our understanding of how fundamental particles can have mass. You might think the history of that discovery would be thoroughly understood and agreed on, but Wells detects a false and seductive mythology: a Eureka moment for Higgs in 1964 followed by 48 years of experimental labour until the triumphant announcement by the ATLAS and CMS collaborations on 4 July 2012.

His article is a good read for anyone unafraid of an equation or two, and his main point is that elucidating the observable consequences of the idea conceived by Higgs (and Brout and Englert) in 1964 required a series of major theoretical advances over the intervening years, and an amount of hard graft at least comparable to that involved in building the experiments. The discovery papers of ATLAS and CMS cite 115 theory papers. Wells lists them in his article. They cover the original ideas, understanding their appearance in a particle collision, what other physics might fake that appearance, what the theoretical uncertainties are, and more. ATLAS and CMS could have cited many more papers, but you have to draw the line somewhere.

The point is convincingly made, and should be taken on board by anyone tempted by the simplistic lone theorist hero and herculean experimentalists mythology.

Wells makes another point, however, with which I disagree. He says that the theory input is so important that

The Higgs boson could not have been discovered experimentally by accident.

I think it could.

The Higgs boson is produced when particles are brought into collision with each other at high energies, as was done at the Large Hadron Collider at CERN. Once produced, the Higgs decays rapidly to other particles, and digging the signs of this decay out of all the other particles produced in the collisions is a large part of the experimental challenge. The Higgs can decay several different ways, and some of them would surely not have been untangled any time soon without a lot of guidance from theoretical predictions such as those described by Wells.

But one of the ways the Higgs can decay is rather striking and is not overwhelmed by fake backgrounds. This is the decay to four leptons (either electrons, muons or their antiparticles). Any experiment at a high energy collider would look for four leptons and measure their mass. In fact this is the measurement I described just last week. The bump at 125 GeV in that plot with the most physics is pretty clear – we would, I am confident, have made that plot and seen that bump, even if we hadnt been looking for the Higgs.

Now it is true that without the theory we might never have built the collider, or ATLAS and CMS. Counterfactual history is tricky. But there are good general reasons for building high-energy colliders they allow us to study the smallest constituents of matter, and we knew that was the case already without help from Higgs. So I think high energy physics would probably have got there in the end.

What is certainly true is that without the theory we would have been slower, and would not have known immediately what that bump was. Wed have been excited about it, and there would probably have been a lot of theories produced very quickly, as there were when we thought we might have another one at 750 GeV. Maybe that is what Wells means without the theory, we could not have understood the implications of the bump, or connected it to the origin of particle masses. In that case I would agree with him.

But the Higgs boson could, and I think probably would, have turned up by accident, nevertheless. And the theorists would have told us what it meant, eventually.

Jon Butterworths book Smashing Physicsis available as Most Wanted Particle in Canada & the US.

Read more: https://www.theguardian.com/science/life-and-physics/2016/sep/18/could-the-higgs-boson-have-been-discovered-by-accident

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