The Higgs Boson

  As an electrical engineer, I'm the closest thing to a physicist some of my friends know.  A few of them therefore asked me for an explanation of the Higgs boson when its discovery was recently announced by the pan-European nuclear research organization CERN.  I had to admit that I hadn't a clue.  I've since sought that clue.

  In exculpation of my ignorance, I should mention that quantum physics—physics at the atomic level—only slowly percolated into the curriculum during my formal education.  In the mid-1940s, when I was in high school, atoms were described very simply: they were like tiny planetary systems.  Electron "planets" circled about a "sun" consisting of protons and neutrons, each of the latter being a proton bound to an electron.  Not so hard to understand.

  In my undergraduate days I was introduced to more complexity: electrons and protons are not solid orbs, but fuzzy entities instead, with dual natures that allow them to act also as waves.  Conversely, light—which I'd always thought of as a wave—has a dual nature as a fuzzy particle: the photon.  My understanding was getting as fuzzy as the particles.

  In graduate school, spooked by the strangeness of the quantum world, I tried to avoid it altogether.  Alas! that was not to be.  During the oral exam in which I was to defend my doctoral thesis and exhibit sufficient knowledge of the science and mathematics underlying it, a perverse examiner asked me a question about quantum mechanics, which had nothing whatsoever to do with my thesis.  I was flabbergasted, unable even to start answering.  My nemesis insisted that I take a graduate course on the subject.

  I thus found out that those fuzzy particles are neither here nor there, but can be everywhere simultaneously, described only by probability distributions of their locations; that trying to pin them down with any precision is a fool's effort, prohibited by quantum laws; and I learned how to derive their probability distributions.  More befuddled than ever, I absorbed enough of this hodgepodge to pass the course and get my degree.  My formal quantum-physics education thus ended in 1956 on a note of heightened incomprehension.

  The field continued to develop rapidly and ever more impenetrably.  New elementary particles were discovered at an astounding rate.  Protons turned out not to be elementary, but made up of quarks.  Two fundamental forces beyond electromagnetism and gravitation were confirmed: the strong nuclear force that binds quarks inside the proton, and the weak nuclear force that accounts for radioactive decay.  These forces were shown to be carried by particles like the photon, which conveys the electromagnetic force. 

  A Standard Model of particle physics was completed by the 1980s, although it took until 2000 for the last hypothesized particle to be verified experimentally.  I show below a  diagram of the Model, which reveals its astounding complexity.  In it, all the matter and force particles are elementary; the only ones of them included in my formal education had been the electron e^- and the photon γ.

The Standard Model of Particle Physics.

[Source: Baggott book referenced below.]

  You might have heard of the other leptons in the Model (besides e^-)—they are neutrinos and muons.  The quarks come in six "flavors" and three "colors."  And not shown are antiparticles, rarely seen in our present universe: every matter particle has one, the positron e⁺ for example being the antiparticle of the electron e^-.  A crazy quilt!  I've continually been puzzled that quantum physics doesn't seem to follow the principle of parsimony, which argues that explanations of nature should be simple.

  Also not shown in the figure is the Higgs boson, another force particle, about which CERN's discovery now forced me to educate myself.  I accordingly read Higgs: The Invention and Discovery of the 'God Particle' by Jim Baggott.  It's a well written book, given the cryptic subject it addresses, yet I stayed bemused throughout, I think not without reason.

  Here's the story as I understand it:  In the early 1960s, Peter Higgs and others independently tried to resolve a contradiction: recent theoretical results seemed to say that certain particles should be massless and therefore should move at the speed of light, but that was known not to be true.  They conjectured the existence of a field, now called the Higgs field, uniformly permeating all of space with inherent energy, which imparts mass to those particles as they move through it, thereby slowing them down; and they speculated that a force particle, now called the Higgs boson, could arise from this field and would be the only direct evidence for it.  In the 1970s, the same conjectures were carried over to the Standard Model as it developed, to explain why all its matter and weak-force particles have mass (the photon and strong-force particles have none).  The Higgs field thus became a linchpin of the Standard Model.  More patchwork on the crazy quilt!

  A folksy tale was contrived by a British physicist in response to a request from a UK minister in charge of appropriating funds to CERN, who had asked for a one-page description of the Higgs mechanism that he could understand.  I transpose the answer to an American setting.

  Suppose you are watching the President enter the House of Representatives chamber to give a State of the Union address.  If the chamber is otherwise empty of people, he would move down the aisle to the Speaker's desk in a trice—the equivalent of a massless particle moving at the speed of light.  However, with a chamber packed with politicians and other officials, the President is enveloped by well-wishers who speak to him and shake his hand, substantially slowing his progress.  Looking from far above, one would see only a bulge of people moving as a wave down the aisle toward the front of the chamber; importantly, no one except the president would actually be moving, the wavelike bulge surrounding him only seeming to do so.  That bulge gives the President a mass he didn't have before, just as the Higgs field imparts mass to a particle moving through it.  Don't ask me how the Higgs field recognizes the type of particle traversing it, thus knowing how much mass to impart; perhaps just as politicians know the importance of someone moving in their midst, thus determining how many cluster about him or her.

  Now suppose the President does not enter the chamber; instead, a rumor starts at the entry door, saying that he is delayed.  Successive groups of different people cluster to hear the rumor as it spreads down the aisle, creating a wavelike bulge appearing to move with it.  It is now not a "presidential particle" moving toward the Speaker's desk—it is a "rumor particle," which could not exist without the field of politicians.  It is analogous to a Higgs boson arising from the Higgs field, which cannot exist without that field. 

  The elation about having seen Higgs bosons stems from knowing that the Standard Model, with all of its intricacies, is further validated; if they had not been seen, the Model would have been seriously undermined.  The observation was a stunning verification of a theoretical conjecture made a half century earlier. 

  I'm pleased that I, as well as quantum physics, have made some progress: the next time I'm asked for an explanation of the Higgs boson, I will be able to say that I have a wisp of a glimmer of a clue.