High-energy particles can collide with others, producing showers of new particles that can be seen in a detector. By reconstructing the energy, momentum, and other properties of each one, we can determine what initially collided and what was produced in this event. In nearly 50 years since supersymmetry was first proposed by Wess and Zumino, no superparticles have ever been seen.
Every so often, an idea comes along in theoretical physics that's undeniably profound. When a single idea can solve a slew of existing puzzles in one fell swoop while simultaneously making new, testable predictions, it's bound to generate a tremendous amount of interest.
It can do more than provide a potential way forward; it can capture the imagination as well. If its predictions are borne out, it could kick off an entirely new understanding of the Universe. This was exactly the situation when physicists hit upon the idea of supersymmetry, or SUSY for short. No one knows why the fundamental particles of the Standard Model have masses that are so small compared to the Planck scale, or why the fundamental constants don't unify, or what dark matter might be.
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But SUSY promised a solution to each of these, while predicting a spectrum of new particles. The masses of the quarks and leptons of the standard model. The neutrinos themselves are at least 4 million times lighter than the electron: a bigger difference than exists between all the other particles. We do not know of any particles heavier than the top quark. The motivation for SUSY has its origins dating back to the early days of quantum mechanics, and the problem of the electron. Whenever you have a charge, it produces both an electric field and a voltage electric potential around it.
Since it has a charge itself, it's capable of feeling the potential that it generates on its own: it has an energy inherent to its own existence. The smaller the size of an electron, the larger its own internal energy would be, which means that if the electron is truly point-like, it has to have an infinite amount of energy inherent to it. Of course, this isn't the case. Visualization of a quantum field theory calculation showing virtual particles in the quantum vacuum.
Specifically, for the strong interactions. Even in empty space, this vacuum energy is non-zero. As particle-antiparticle pairs pop in and out of existence, they can interact with real particles like the electron, providing corrections to its self-energy that are vitally important. Clearly, that isn't right! The way out was the quantum mechanical existence of antimatter , and of the positron or the anti-electron in particular.
Not only can the electron produce a photon to cause it to interact with itself, but it can also annihilate with the positron in an electron-positron pair fluctuation, leaving only the "fluctuation" electron behind. When you do the calculation, you find that these two contributions nearly cancel, leading to the electron's tiny size despite its relatively enormous charge. There is certainly new physics beyond the Standard Model, but it might not show up until energies far, far greater than what a terrestrial collider could ever reach. Still, whether this scenario is true or not, the only way we'll know is to look.https://unkonseire.cf
Higgs boson is too saintly and supersymmetry too shy
In the meantime, properties of the known particles can be better explored with a future collider than any other tool. But what does that have to do with SUSY? All you'd need is a superpartner particle for every one of the Standard Model particles that exists. The Standard Model particles and their supersymmetric counterparts. Supersymmetry is an idea that hopes to improve on the Standard Model, but it has yet to make successful predictions about the Universe in attempting to supplant the prevailing theory.
Sure, you have to double the number of known fundamental particles, creating a superpartner particle counterpart a super-fermion for each Standard Model boson; a super-boson for each Standard Model fermion for every one that's known. But this symmetry between fermions and bosons can, in theory, reduce those particle masses all the way down to the values we observe. If these new supersymmetric particles come in at approximately the electroweak scale, or between about GeV and a few TeV, they can also:. Physics seems to be in pretty good shape.
We've basically confirmed all of the main features of the "Standard Model" of physics. We've now discovered every particle in the model, with no leftovers. But now isn't the time to get complacent. There are still lots of unanswered questions.
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You may have heard some murmurs about a popular idea known as Supersymmetry or "SUSY" to its friends. There's a lot riding on the possibility of SUSY, including a few problems that are — ironically — caused by the discovery of the Higgs itself. So today we're going to figure out:. This being io9, the particle zoo is probably second nature to most of you, but in case it isn't, let me give you a 10 second backgrounder to get you ready for SUSY.
The world of fundamental particles is filled with cool sounding things like quarks and gluons, but at the end of the day, most of the interesting distinctions between particles can be found by putting them very neatly, and quite unambiguously, into two different piles known as Fermions and Bosons.
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The Fermions are the most familiar particles: electrons, quarks, neutrinos and the like. These are the particles that make up matter. Quarks, for instance, make up protons and neutrons which are, themselves, also Fermions. Bosons, on the other hand, are the particles of force: photons, the W and Z Bosons, gluons, and the Higgs. The difference between the two groups comes down to a very weird property — one that I've written about before — known as spin. All known particles have an intrinsic, unchanging spin to them. Except for the Higgs, which doesn't spin at all. Since the Higgs has zero spin and zero is an integer, the Higgs gets lumped in with the other Bosons.
Those differences seem like the sort of trivia only the nerdiest physicist could get excited about, but they have enormous consequences. The distinction manifests itself when you switch one particle with another of the exact same type. That's it. That's literally the most important difference between the two, and yet, that -1 is ultimately responsible for something known as the "Pauli Exclusion Principle," which gives rise to everything, from all of chemistry to the behavior of White Dwarves. The Higgs is a pretty important particle in the scheme of things. Did you see the excitement from the Physics community when it was discovered?
It's like finding a mint condition Millenium Falcon still in its original packaging. We were fairly confident that the Higgs would be discovered.
It is a linchpin in the Standard Model, something that seemed absolutely essential to explaining why the weak force was so weak. Related to that, the Higgs also explained where the masses of particles come from. That's because the Higgs interacts with just about everything. But these interactions are a two-way street.
Introduction to Supersymmetry
But here's the weird part. The contributions from other particles can either add extra or subtract from the total. The Higgs mass that we measure at the LHC isn't necessarily the real mass that it would have if we could strip away all of those interactions. This is roughly equivalent to when you go to the doctor's office and they let you leave your clothes on when they weigh you. Whatever weight the scale reads — the weight that's measured by the rest of the world — is actually more than your "bare" mass.
To get your bare mass, you'd need to subtract the weight of your clothes. One of the strange things about the universe is that particles and antiparticles constantly pop into existence. For the most part, we don't notice them since they don't last for very long, but when they interact with particles, those interactions can add or subtract energy or what we measure as mass from other particles.
For the Higgs, this correction should be huge , generally of order the Planck Mass — a hugely gargantuan mass by particle standards that basically sits at the limits of our ability to reconcile quantum mechanics and general relativity. To put some numbers on it, suppose the bare mass of the Higgs is something like 2,,,,,, GeV, the interaction with electrons and positrons might subtract 2,,,,,, GeV, yielding the observed value of GeV.
The fact that the numbers come so close to matching — but don't exactly match — is too much to accept by chance. The odds of something like that happening in nature by mere chance is so remote as to be laughable. I only gave you the correction for electrons and positrons, but there are lots of other types of particles out there.
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Each and every one is going to interact with the Higgs and add a correction to the mass. There's a weird wrinkle to all of this. Those plus and minus 1's are going to be drafted into service again; they just play a slightly different role this time around. For each species of Fermion, we subtract from the bare mass to get the observed mass —- that's why I subtracted when talking about electrons —- and with Bosons we add. And for each, we add or subtract roughly the same amount of mass. In the Standard Model at least, there aren't equal numbers of Fermions and Bosons.