Yesterday was, for many physicists (and physics students), as a friend put it, "a bit like Christmas", and I think it is safe to bet that quite a few at CERN woke up today with a very Christmassy hangover. But, now that the party is over, a question arises (as often on the morning after): what exactly did happen yesterday?
If you look at the headlines of the science sections on the main news websites, it goes something like this: "strong evidence for 'God-particle' found". In passing, I will say that I was quite unimpressed at the media's use of the phrase "God-particle": it is probably worth repeating, and even hammering the point that this was simply a catch phrase designed by publishers to sell a book (the God Particle, by Nobel laureate Leon Lederman, who initially referred to the Higg's as the "God-damned particle", because of all the trouble physicists went through to find it), and that no scientist has ever used it.
The Higg's field is, according to theory, what gives particles their masses: I really don't see anything mystical about that. But my main problem with this name is not that it is historically just a marketing tactic (after all, the name Big Bang was initially coined by adversaries of the theory to deride it), but that it erroneously presents theoretical physics as a quest for "transcendent" understanding of Nature, whereas what is truly fascinating about the discipline is that it investigates what we daily take for granted (concepts such as mass, space, time), rather than dwell in the lofty heights of theology, and ask whether God is One or Three, or Both. But enough ranting, and back to the science.
Essentially, three questions come to mind: what is a Higgs boson (and why the fuss)? What exactly is it that was discovered yesterday? And how will that affect future research?
As for the first question, I'll admit that I can only answer with analogies I have read on other websites, because quantum field theories are simply way beyond the curriculum of undergrad physics. In a nutshell, the Higgs is responsible for other particles' masses. One of the more frequent analogies explaining how this happens is the following: imagine the particles in the early Universe as a crowd in a street, with everyone running about (at the speed of light...) in random directions, minding there own business. Suddenly (about a trillionth of a second after the Big Bang, when electroweak symmetry is broken), a multitude of movie stars (the Higgs bosons) walks onto the street, and the crowd starts forming a throng around each of them, slowing down the people/particles who gather round to look. How much each person/particle is slowed down depends on how big a fan he/she is of the stars in question, and the amount by which it is slowed down is linked to its mass: photons, for instance, have no mass, so in the analogy they would be represented by people who have no interest in film stars, and therefore continue running along their merry way (at the speed of light), casting a disgusted look at the gawking fans.
The reason for the excitement surrounding the Higgs in the physics community is that, apart from explaining mass (which is quite a big thing), it is also a very old prediction of the Standard Model (dating from the sixties, before it was even the SM was completely formulated), and one that a growing number of people thought would never be observed (including Stephen Hawking), so strange and abstract the idea of the Higgs field seemed. But discovering a good candidate for the Higgs has stunned even those who thought the prediction to be right, so long had the wait lasted, and quite a number of physicists (Brian Cox among them) believe that this may turn out to be one of the most important discoveries in particle physics in the past fifty years.
And now for the second question. From what I understand of yesterday's announcements, what has definitely been established is the following:
1) A new particle has been found;
2) It is a boson (it has integer spin), although physicists are as yet unsure of the exact value of its spin (the Standard Model Higgs is predicted to have spin-0);
3) It is within the expected energy (and, therefore, mass) range for a Higgs (125 GeV/c²).
What is unclear for the moment is whether it interacts with other particles as a Higgs would, and if it is indeed a Higgs, whether it is a "Standard Model Higgs" or a "Supersymmetric Higgs". The first problem is actually the reason why scientists have all been very careful to specify that what they have found with "five-sigma" (99.99994%) certainty was a "Higgs-like" particle, or a particle "consistent with being a Higgs", and not simply a Higgs: indeed, for this to be certain, observations of the new particle interacting with other, known particles, would be needed, since the Higgs is supposed to interact with all massive particles (meaning for instance that the Higgs does not interact with photons), being responsible for the property of mass itself. The second problem is also of crucial importance, because discovery that the Higgs is not unique and possesses "superpartners" would be important evidence in favour of Supersymmetry (affectionately nicknamed SUSY, rather than SS, which has somewhat more sinister connotations).
Which finally leads us to the last question: what will happen next?
Most researchers yesterday insisted that the discovery was really exciting more as a beginning, an opening up of new horizons, than as an end in itself (in other words, physicists are thankfully far from being out of a job). Indeed, there is still much to learn: about the particle itself, of course, but also about potential ramifications into other fields of research, such as the quest for dark matter and SUSY (the two are linked because "supersymmetric partners" of known particles are considered to be potential candidates for the "missing matter" of the Universe). So, as head of CERN Rolf Heuer said, "Ask me again in three, four years".