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?

[ This blog is dedicated to tracking my most recent publications. Subscribe to the feed to keep up with all the science stories I write! ]

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]

Captain Picard may be a little confused.

Today, researchers with the LHCb experiment at CERN announced the confirmation of a weird object that first appeared in detectors in 2008. This object is made up of four quarks, where other particles are made of two or three quarks (or zero, in the case of electrons, neutrinos, and the like). But what sort of beast is this? As is often the case, more work is needed before we can say for ccertain.

With that much data, physicists were able to determine the composition of the Z(4430): it consists of a charm quark, a charm anti-quark, a down quark, and an up antiquark. The “4430” part of the name indicates its mass: 4,430 million electron-volts, which a little more than four times the mass of a proton (938 million electron volts). The combination of quarks gives the Z(4430) a negative electric charge, hence the “-” in the label. The particle is highly unstable, so none of them are expected to be seen in nature. [Read more…]

Four quarks for Muster Mark!

question box from Super Mario BrothersWriter/editor David Manly posed a series of questions to scientists and writers, soliciting short responses on topics of broad interest. Those interviewed were shark researcher David Schiffman, paleontology writer/sauropod snogger Brian Switek, and me. If you want to know who would win an arm-wrestling contest between a human and a Tyrannosaurus, or how we know black holes exist if we can’t see them, this post is for you.

A Manly conversation