Particle physics is a study in science history, philosophy, and human perseverence in the face of the unknown.
Particle physics is a tricky subject for two important reasons. First, it is still incomplete. Even though particle physicists have been looking for the Higgs boson since 1964, (almost) finding it in 2012 closed only a chapter in the book of the subject. There are so many other unknowns, so many forces and properties that physicists are still looking for, and that's not to mention the fact that we also don't know what else we might not know!
Second, it is a vast field that addresses everything about the Universe - and I mean everything! It goes from trying to explain how the galactic filaments - the largest superstructures in nature known to humankind - formed to how the smallest particles interact with each other. Everything that you and I know about the world around us involves particle physics. And in all this particulate mess, it is just as easy to stumble upon order as it is to descend into chaos.
Physicists around the world are working to resolve such traps, to find patterns in nature that could indicate which particle does what, its properties, etc., and then use them to understand our place in the universe. It is not any more as easy as it was for Newton to deduce the existence of a gravitational force by looking at a falling apple. Now, the number of patterns has grown to encompass what scientists call a "zoo of particles". And while they began their quest on many a successful note, it is far from over.
Starting with the discovery of the electron, then the protons and neutrons, then the fundamental forces, then the force-carrier particles, and then all of their various interactions with themselves and each other, we have come a long way in deciphering the weave of nature's fabric. Today, particle physics research is much more organised, and much less groping in the dark, than it was in the past. We are much less confused, but we also have much more to make sense of.
Strong centres of research exist in the USA, Europe, and Japan. You will be familiar with the names of some of the most famous scientific experiments that are hosted in these countries. The Fermilab, Illinois, is the home of the now-retired Tevatron; CERN, France-Switzerland, hosts the famous Large Hadron Collider (LHC) experiment; the KEK laboratory, Tsukuba, is one of the world's largest particle physics laboratories.
Other less famous but equally important experiments and labs exist around the world. In India, there are the Tata Institute of Fundamental Research (TIFR), the Institute of Mathematical Sciences, and the Institute for Plasma Research, amongst others.
Most of the work being done in these labs can be broadly divided into two kinds: verifying existing “facts” and looking for new ones. For instance, the discovery of a Higgs-boson-like particle was announced by CERN on July 4, 2012, at the 5-sigma confidence level. While this rules out all doubt that such a particle was, indeed, spotted, other particle colliders around the world will attempt to recreate the boson. It isn’t enough that one lab has spotted it; being able to recreate the boson under different conditions implies its formation’s universality and, thus, its factitude.
The looking-for-new-facts involves a lot of planning, research, and development. Experiments that have verified a theory’s validity in the past will be relied on while scientists think up new experiments that can build on the previous ones’ findings. As Kajari Mazumdar, a physicist from TIFR, said, "Yesterday's signal is today's background."
Consider the Higgs-boson example again: Now that the LHC has confirmed that the particle can be found at around 125 billion electron-volts (GeV), new colliders will be thought up to recreate that energy, and even provide a cleaner collision environment for the particle to manifest itself. This will simplify research focused solely on the properties of the elusive particle.
The current particle physics research landscape, after all these years and the resilient involvement of thousands of scientists and engineers around the world, is unraveling itself to demand certain attitudes.
For one, the Standard Model, which is the unifying framework of rules that governs the “zoo of particles”, is finding itself validated after every experiment. While you’d think this was purely good news, physicists think otherwise. If only they could find a chink in its armour, they’d know where to look next for a New Physics, as it were. But its theory is holding firm: the model is able to explain the behaviour of the four fundamental forces, the modes of interactions of and between particles, and the properties of individual properties themselves.
The questions it is unable to address are the ones whose answers scientists haven’t built experiments to answer yet. And now that the Standard Model almost stands completed, very few ideas exist about where to look next, or even what at.
The second set of attitudes is concerned with spotting highly elusive particles, ones that decay in fractions of a trillionth of a nanosecond after having been spotted once in some billions of collisions. Verily, these are particles that simply pop in and out of existence, so how could they be important?
Well, their discovery could throw light on when and why the physics of the Standard Model could fray, and the fraying is important because, then, a new super-theory will make its need felt.
Some of the questions such a super-theory will seek to answer will be:
1. Why do particles manifest themselves in families (or types) of three?
2. Why the gravitational force so much weaker than the electroweak force?
3. Why is there more matter than antimatter in this universe?
4. What is dark matter?
5. Can Einstein’s general theory of relativity – which describes the cosmos – and quantum mechanics – which describes the microcosm of particles – ever be reconciled?
6. Why do those particles, on which the electroweak force has acted, have their left and right swapped?
One of the most popular super-theories is Supersymmetry or SUSY for short. This theory predicts that for every fermion, a kind of fundamental particle, there must exist a heavier counterpart boson. This would explain away many mass-related inconsistencies observed in nature, and also provide a setting for the highly sought-after WIMP (!) to show itself.
So… welcome to the world of particle physics.