The GUTsy effort to unify the quantum forces

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A GUT feeling about physics

Scientists want to connect the fundamental forces of nature in one Grand Unified Theory

For Symmetry Magazine:

The 1970s were a heady time in particle physics. New accelerators in the United States and Europe turned up unexpected particles that theorists tried to explain, and theorists in turn predicted new particles for experiments to hunt. The result was the Standard Model of particles and interactions, a theory that is essentially a catalog of the fundamental bits of matter and the forces governing them.

While that Standard Model is a very good description of the subatomic world, some important aspects—such as particle masses—come out of experiments rather than theory.

“If you write down the Standard Model, quite frankly it’s a mess,” says John Ellis, a particle physicist at King’s College London. “You’ve got a whole bunch of parameters, and they all look arbitrary. You can’t convince me that’s the final theory!” [Read the rest at Symmetry Magazine…]


Of GUTs, glory, and the death of a proton

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Do protons decay?

Is it possible that these fundamental building blocks of atoms have a finite lifetime?

For Symmetry Magazine:

The stuff of daily existence is made of atoms, and all those atoms are made of the same three things: electrons, protons and neutrons. Protons and neutrons are very similar particles in most respects. They’re made of the same quarks, which are even smaller particles, and they have almost exactly the same mass. Yet neutrons appear to be different from protons in an important way: They aren’t stable. A neutron outside of an atomic nucleus decays in a matter of minutes into other particles.

What about protons?

A free proton is a pretty common sight in the cosmos. Much of the ordinary matter (as opposed to dark matter) in galaxies and beyond comes in the form of hydrogen plasma, a hot gas made of unattached protons and electrons. If protons were as unstable as neutrons, that plasma would eventually vanish.

But that isn’t happening. Protons—whether inside atoms or drifting free in space—appear to be remarkably stable. We’ve never seen one decay.

However, nothing essential in physics forbids a proton from decaying. In fact, a stable proton would be exceptional in the world of particle physics, and several theories demand that protons decay.

If protons are not immortal, what happens to them when they die, and what does that mean for the stability of atoms? [Read the rest at Symmetry…]

The particles of the the Standard Model and its simplest supersymmetric version. [Credit:  Pauline Gagnon]

The particles of the the Standard Model and its simplest supersymmetric version. [Credit:
Pauline Gagnon]

Symmetry and elegance have proven to be a very successful way to think about the physical Universe. Arguably the greatest successes in 20th century particle physics came from translating mathematical symmetries into predictions about the results of particle collisions. However, not every symmetry thus far has led to a successful theory, and one of the frustrations is that a natural consequence of a symmetry in the theory of relativity hasn’t produced the predicted particles. The currently unfulfilled theory is known as supersymmetry (or SUSY), and so far none of its predictions have borne out experimentally.

However, a completely analogous version of SUSY could exist in certain exotic superconductors. This is not built out of elementary particles, but out of interactions between electrons and atoms, giving rise to a set of particle-like quantum excitations known as quasiparticles.

The new paper discussed the idea of emergent SUSY-like behavior in topological superconductors. In these systems (described in more detail in the sidebar story), the interior of the material conducts electricity without resistance, but the outside is an ordinary conductor. The authors argued that experimentally observed magnetic behavior on the conducting surface could be interpreted super symmetrically. It also exhibits a breaking of SUSY due to the fundamental difference in interior and surface behavior of the system.

In this view, the magnetic excitations (acting like bosons) on the surface are SUSY partners with the topological superconductor quasiparticles, which are fermions. [read more…]

Supersymmetry in…superconductors?

The Standard Model (SM) of particles and interactions provides a successful description of most of the matter we know of. However, physicists have known for many years that it is not complete: the SM predicted massless neutrinos, and has no place for dark matter. A new result from the BaBar experiment at the Stanford Linear Accelerator Center (SLAC) could possibly provide another problem for the SM—and would place severe constraints on a popular alternative theory, supersymmetry (SUSY)….

Read more at Ars Technica.

Too many heavy particles could mean trouble for the Standard Model