The weird new physics of neutrinos

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Already beyond the Standard Model

We already know neutrinos break the mold of the Standard Model. The question is: By how much?

For Symmetry Magazine:

Tested and verified with ever increasing precision, the Standard Model of particle physics is a remarkably elegant way of understanding the relationships between particles and their interactions. But physicists know it’s not the whole story: It provides no answer to some puzzling questions, such as the identity of the invisible dark matter that constitutes most of the mass in the universe.

As a result, in the search for physics beyond the Standard Model, one area of notably keen interest continues to be neutrinos.

In the Standard Model, neutrinos come in three kinds, or flavors: electron neutrinos, muon neutrinos and tau neutrinos. This mirrors the other matter particles in the Standard Model, which each can be organized into three groups. But some experiments have shown hints for a new type of neutrino, one that doesn’t fit neatly into this simple picture.

[Read the rest at Symmetry Magazine]

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Meet the glueball, the missing Standard Model particle

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Glueballs are the missing frontier of the Standard Model

There should be particles made entirely of gluons, but we don’t know how to find them

For Ars Technica:

The discovery of the Higgs boson was rightfully heralded as a triumph of particle physics, one that brought completion to the Standard Model, the collection of theories that describes particles and their interactions. Lost in the excitement, however, was the fact that we’re still missing a piece from the Standard Model—another type of particle that doesn’t resemble any other we’ve yet seen.

The particle is a glueball, but its goofy name doesn’t express how interesting it is. Glueballs are unique in that they don’t contain any matter at all: they have no quarks or electrons or neutrinos. Instead, they are made entirely of gluons, which are the particles that bind quarks together inside protons, neutrons, and related objects.

Particle physicists are sure they exist, but everything else about them is complicated, to say the least. Like so many other exotic particles (including the Higgs), glueballs are very unstable, decaying quickly into other, less massive particles. We don’t have any ideas about their masses, however, which is obviously kind of important to know if you want to find them. We also don’t know exactly how they decay, making it hard to know exactly how we’ll identify them in experiments. [Read the rest at Ars Technica….]

Why are there three copies of each type of particle?

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The mystery of particle generations

Why are there three almost identical copies of each particle of matter?

For Symmetry Magazine:

The Standard Model of particles and interactions is remarkably successful for a theory everyone knows is missing big pieces. It accounts for the everyday stuff we know like protons, neutrons, electrons and photons, and even exotic stuff like Higgs bosons and top quarks. But it isn’t complete; it doesn’t explain phenomena such as dark matter and dark energy.

The Standard Model is successful because it is a useful guide to the particles of matter we see. One convenient pattern that has proven valuable is generations. Each particle of matter seems to come in three different versions, differentiated only by mass.

Scientists wonder whether that pattern has a deeper explanation or if it’s just convenient for now, to be superseded by a deeper truth. [Read the rest at Symmetry]

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