During the International Europhysics Conference on High Energy Physics hosted in late July at Grenoble, the latest data from the world’s most powerful particle accelerator was presented. After years of waiting for the Large Hadron Collider (LHC) to be built and brought up to operational levels, and after numerous frustrating technical setbacks, the European Organization for Nuclear Research (CERN) was ready to present its first tenuous conclusions about the Higgs boson. It was there that they dropped the bombshell: CERN stated that there was a 95 per cent chance that it did not exist, effecitlvey ruling out its existence.
The Higgs boson, popularly known as the “god particle” because of its supposed role in endowing everything in the universe with mass, has been furiously searched for since the postulation of its existence in 1964. The Standard Model predicts a menagerie of subatomic particles. Of these, the Higgs boson is the only one yet to be confirmed. As a scientific theory, the Standard Model is the most thoroughly tested in all of human history. It successfully unites electromagnetism, the strong nuclear force that keeps atomic nuclei together, and the weak nuclear force that controls radioactive decay under one theoretical framework.
The Standard Model essentially says that all matter in the universe is composed of varying combinations of fundamental units called fermions of which there are two types: quarks and leptons. There are six types of quarks and leptons respectively, with each also having antiparticles. The combination of these 24 different fermions is what gives rise to the matter in the universe. Particles such as protons are composite particles; those made from different quark combinations are collectively referred to as “hadrons”.
Another important part of the Standard Model is the idea that all of the forces we are familiar with, such as the electromagnetic radiation that makes up visible light and enables wireless internet, arise as the result of interactions between force-carrying bosons. This is where the Higgs boson fits into the picture: it is supposed to be the force carrying particle that brings mass into being.
Much of the theoretical work that goes into the Standard Model entails predicting the characteristics of these bosons. However, for any scientific prediction to be considered valid, it must survive the process of experimental verification. For the Standard Model, this requires that the existence of these theoretical particles is demonstrated. For most of these particles, under normal conditions, evidence of their existence cannot be observed. However, by providing high amounts of energy, these exotic particles can be created in a laboratory.
Unfortunately for Standard Model experimentalists, this requires building ever-larger and more expensive particle accelerators, which smash together hadrons at the speed of light. The LHC is the latest and greatest particle accelerator to date, and uses $100,000 worth of electricity to get beams of atoms moving one way or another around a 27 kilometer track just about three meters per second shy of the speed of light. These two beams are then smashed together, and scientists sort through the resulting hadron debris to figure out which particles were generated in conditions that have not existed since microseconds after the big bang. For the LHC, there are about 40,000 individual collisions per second, which makes for an awful lot of data to sift through.
Over the course of the past three years, the LHC created billions of collisions, each of which generates thousands of particles. The sheer volume of the data generated is daunting, to say the least. Even with the most sophisticated detectors ever created, it is extremely difficult to distinguish a true hadron detection and to do so requires thousands of hours of computation. The scientists at CERN have even started the LHC@home project, which uses the processing power of personal computers around the world to assist with these calculations.
Even with all that data generation and processing, the successful identification of an as-yet-undiscovered particle such as the Higgs boson can require years of continuous collisions, to allow the signal to rise up above the extraneous data, such as those collected from the collision of other particles. For a new particle to be considered confirmed, it must pass the so called “5-sigma” rule, demonstrating a 99.99995 per cent likelihood that the observed results are not more easily explained by background noise.
Even with this commitment to statistical rigour, sometimes there can be anomalous signals within this noise. Earlier this year, a leak from CERN showed data that matched exactly what the Higgs boson would look like. However, as more data was collected, those promising conclusions faded into statistical insignificance.
It is in this conservative experimental context that the significance of the conference’s summaries can be fully appreciated. Discovering with 95 per cent confidence that the Higgs boson probably does not exist is practically the raison d’etre of the LHC, because after nearly fifty years of waiting, scientists finally had the ability to test a central tenet of the Standard Model. Even though the Standard Model is the most viable theory thus far, new discoveries such as this show us that our fundamental understanding of the universe is incomplete.
In terms of the underlying physics involved, this non-discovery lends credence to other so-called “Higgsless” models. These theories include the idea of technicolour, which creates mass through a different (and more complicated) method than the Higgs boson. Other alternative theories include the possibility of inducing mass through an interaction with a fourth spatial dimension, or even a theory called “loop-quantum gravity”, which posits all of space-time as being made up of tiny quantized, interwoven, fuzzy loops, with the interaction of these loops giving rise to all the phenomenon in the universe, including mass.
Although this is an exciting discovery for physics, it is understandable if the enthusiasm is not contagious. To many, a project of this scale is simply a waste of resources. However, disproving the Higgs boson is equally as important as giving evidence for its existence. This new discovery opens the door to other untested and novel theories of the nature of the universe. Although these studies are admittedly esoteric, their findings have far-reaching consequences. The thing to keep in mind about pure research, such as this, is that it’s always unpredictable. The technology behind MRIs arose from research not intended for practical use; its existence was only made possible through pure, esoteric, scientific inquiry.
As we move into the future, the words of Socrates come to mind: “As for me, all I know is that I know nothing.” For all of its successes, the Standard Model is completely incompatible with general relativity, which accurately describes the structure of the universe at its largest scale. Even current “theories of everything” such as String Theory (which has the Standard Model built into it) are incapable of accounting for astronomically observed realities like dark matter and dark energy. The sea of our ignorance is vast; but with each discovery such as this, the shores of our limited knowledge expand ever so slightly.