Saturday, July 7, 2012

Higgs Bosons: What's the Big Deal?

The news wires have been buzzing this week with the possible discovery, at the Large Hadron Collider (LHC) in Switzerland, of the long-sought Higgs Boson—aka the “God particle.” Just that nickname is enough to set journalistic hearts a-flutter. But, as always in high-energy physics, there’s more to the drama than meets the eye via standard news accounts. This is not to say that I, a mere dilletante, really understand it, but reading lots of accounts and seeing several videos has made some things clearer. Perhaps I can convey that to a few readers.
            To begin with, the real action here lies with the proposed Higgs field, the Higgs Boson being only an indication that the theorized field actually exists. But the Higgs field is not like the usual fields—the magnetic field around earth, or the gravitational field around our sun, or an electromagnetic field around a generator—we’re familiar with. Those fields require an energy source, like the sun, to generate them; furthermore, the size of the force (of gravity say, from the sun) varies with the distance from the energy source. So, the farther we get from the sun or the earth, the less force we feel from its gravity field. In short, most fields dissipate with distance because the number of particles constituting the field (virtual particles) is fewer (this last is due to the quantum understanding of fields, which used to be thought of as continuous, but are now thought of as composed of particles, like all else).
            The Higgs field is not like that. Theoretically at least, the Higgs field remains the same throughout the universe even though there’s no source generating it (if I understand it correctly, the Higgs field would have been generated in the first nano-seconds of and by the Big Bang). Its force doesn’t dissipate with distance because of this lack of a specific energy source. It’s everywhere.
            This means something fundamental: there really is no empty space anywhere. The entire universe and all in it is saturated with a Higgs field (or as many as five Higgs fields) all the time. And of course, like any field, what makes up a Higgs field are Higgs bosons (subatomic particles). It is believed that these Higgs bosons interact with all subatomic particles, dragging on them, thus giving them their mass. Some have compared the Higgs field to an ocean of molasses; any particle with mass that tries to get through it feels a drag on itself—and this is what is meant by its mass. The only particles that don’t get dragged on by a Higgs field are the virtually massless ones: photons (light particles), gluons (force particles between quarks) and gravitons (the theorized and yet undiscovered particles that express gravity). The sun-generated neutrinos are also, like ghosts, exempt from the Higgs field’s drag. So, because of the Higgs bosons dragging on it, a particle such as a top quark (quarks are the components of protons) has a very large mass—indeed it is 350,000 times the rest mass of an electron (even though both particles are about the same ‘size.’)* 

            So why is it so important to find evidence of Higgs Bosons and hence Higgs fields? There are two basic reasons. First, finding the boson will firmly, experimentally establish that the Higgs field exists, and therefore, that it is what gives matter its fundamental property of mass. This is key because in order to rationalize and complete the standard theories of particle physics, an explanation is needed for this phenomenon of mass. That is, why should some subatomic particles have no mass (such as photons), while others have varying degrees of mass (such as the W and Z bosons carrying the weak nuclear force).  This would then fill out the Standard Model in a way that would be impossible if the Higgs Boson could not be detected.
            Second, there is a related and perhaps even greater problem that the “b” portion of the Higgs Boson experiment is attempting to solve: the problem of symmetry. Symmetry gets to the fundamental problem of why there is matter in the first place. In the Standard Model, that is, matter and its oppositely-handed twin, antimatter, are conceived as symmetrical twins. For every piece of matter, there is a corresponding piece of anti-matter, and when the two meet each other (as has been demonstrated by experiment), they wipe each other out. The question is, why, if the two are equal or symmetrical, there is so much more matter than antimatter in the Universe we know? And related to this: given that there was, in the very first moment of the Big Bang, also symmetry between the force particles, and hence between the forces they convey, why are there differences now? That is, at the first moment of creation, photons were the same as the W and Z bosons. There was no distinction between the weak nuclear force (W & Z bosons being its messenger particles) and the electromagnetic force (photons being its messenger particles). But there is now.
            The big question thus becomes: how did this apparently universal symmetry yield to the Universe we have now? What gave matter its edge, its ability to exist? What gave the Universe its ability to produce all the matter we see, including ourselves? Why didn’t it remain perfectly symmetrical? The physicist Michio Kaku, talks about this in terms that would almost convince one he was talking about God or Genesis. He refers to the physicists’ “dream of perfect symmetry” at the beginning of the Big Bang where everything in the Universe would have been the same. He calls it a state of “perfection” where particles and forces and fields were all the same. But then something, some slight “imperfection,” caused the Universe to fall into a less symmetrical state. Some tiny fluctuation led to the appearance of distinction:  distinct forces, distinct fields, and matter itself with its myriad distinctions. All of which happens in logical sequence leading eventually to stars, galaxies and us, which means, says Kaku,
            “..everything we see around us is nothing but a fragment of that original perfection.”
            It is this fall into asymmetry and all the rest of our Universe that proceeds from it, that physicists find fascinating, and that the discovery of the Higgs boson may help them, and us, understand.            
            There is more to this, of course, and as one goes deeper it gets very complex and very mathematical. But briefly, there is a relatively new theory called supersymmetry, or SUSY, according to which all the currently known particles have heavier supersymmetric partners, known as “sparticles:” quarks have their “squarks” and photons have their “photinos.” And it may account for nature’s apparent preference for matter over antimatter by positing not one but five Higgs fields with asymmetry built-in, thus giving rise to the excess matter we see. All this requires that physics would have to go way beyond the Standard Model as it is now conceived. But that could be one perverse result of the LHC experiments. For if, as now seems possible, the new particle recently announced at the LHC is not a standard Higgs Boson, fitting perfectly into the Standard Model, but rather a strange particle with an odd decay pattern, well then it’s a whole new ball game. As one physicist put it recently:

            “The Higgs sector particle not being the simplest Higgs boson would be the first indication that, yes, there is new physics out there. And that would provide tremendous momentum to the whole field.” (Christian Science Monitor, July 5, 2012)
The discovery of the ‘God particle’ would, in that case, turn out to be not the satisfying vision capping a century’s long search, but in fact, the beginning of an entirely new quest and new model—one that might finally be able to account for “dark matter” (fully 84% of the matter in the Universe, about which almost nothing is known), gravity (and its messenger particle the ‘graviton’), and the deep conundrum of matter itself.
            So stay tuned.

Lawrence DiStasi

[i] Just to keep things clear, in the so-called Standard Model of quantum physics, there are three sorts of particles: 1) matter particles like quarks, and electrons; 2) force particles (akin to lumps of energy) like photons, gluons, and W and Z bosons; 3) the sought-after and possibly found Higgs particle. The last two can all be classified as “bosons,” because they have the remarkable property of being able to occupy the same place in space. 

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