Don Lincoln

Don Lincoln is a Fermilab scientist.

Subatomic chimeras

In biology, a chimera is a creature whose cells contain the DNA, combined in utero, of two distinct individuals. In today’s column, we describe leptoquarks, a hypothetical new particle that combines the properties of both quarks and leptons. In mythology, the chimera is a beast that is part lion, part snake and part goat. However, in modern times, the term has come to mean any organism that consists of cells from two distinct organisms. Inside the womb, two organisms merge…

What is a WIMP?

Physicists — especially particle physicists — have a habit of choosing colorful names for their various topics of studies. MACHOs and WIMPs are two terms commonly used in dark matter studies. Today’s column tells us what a WIMP is. If you want to understand dark matter, you need to understand terms such as MACHO and WIMP. It’s enough to recall one of those 1970s comic book advertisements for Charles Atlas’ body building program (well, for those of us of a…

The weak force loves particles that spin in one direction but completely ignores particles that spin the other way. In today’s article, I describe a search for a particle that would interact with the ignored spin. Of the four known subatomic forces, the weak force has what seems to be a particularly bizarre behavior. It’s a lefty. What exactly does that mean in the subatomic realm? To understand, you need to remember that fundamental particles spin and that they spin…

An electronvolt, or eV, is the amount of energy an electron or proton gains when accelerated by a one-volt battery. It is a convenient unit for particle physicists to use when they use electric fields to make beams of high energy: If they know the strength of the battery, they know the energy of the beam. TeV. GeV. eV. You don’t have to have read many Fermilab Today articles to have encountered these terms. So what the heck are they?…

Excited quarks are a hypothetical state in which (a) quarks contain within them smaller particles and (b) energy is added to the quarks’ hypothetical constituents and is thus added to the quark. Since E = mc2, more energy in the quarks means they have a higher mass. Therefore scientists look for high-mass quarks that decay by emitting a photon and a regular quark. It is well known that the Standard Model of particle physics is incomplete and that it is…

Subatomic particles like electrons and muons act like tiny magnets. The strength of the magnet is affected by virtual particles. This effect is well known and can be calculated to a precision better than a part in ten billion. A niggling discrepancy between the prediction and measurement of this quantity has the potential to point to physics beyond the Standard Model. Fermilab’s Muon g-2 experiment is poised to study this vexing question. If you take an electrical charge and set…

Learning to connect the dots is one of the first artistic tasks a child accomplishes. In today’s article, we learn how physicists accomplish the same task for a much more complicated puzzle. When two protons collide in the center of the CMS detector, the collision energy can create hundreds of electrically charged particles. These particles roar through the apparatus, crossing individual detector elements. Each particle marks the location of its passage, leaving a string of dots that can be seen…

While Einstein’s theory of special relativity is one of the most mind-bending and nonintuitive ideas of the last century, it turns out that there is a single insight that makes it all far more sensible. Over the past few Physics in a Nutshell columns, we have talked about Einstein’s theory of special relativity and how the operational experience of particle accelerators shows that the theory is true. But there’s a difference between knowing that something is true and understanding why…

In the two decades that have passed since the discovery of the top quark, many things have changed, including the top quark’s transition from newly discovered to well-studied particle. I remember the day in 1995 when the discovery of the top quark was announced at Fermilab. There were reporters. There was champagne. There was a raucous party. It was a big deal, the likes of which are seen once every decade or two. At the time, the top quark discovery…

The twin paradox is a classic seeming conundrum of Einstein’s theory of special relativity. Today’s column explains why it is important that the word “seeming” is added. In reality, there is no paradox. In my last column, I discussed the fact that time passes slower for clocks that are moving at high velocity, and I showed that the Fermilab MINOS beamline proves that the predictions of relativity are right. However, one must be very careful. The “relativity” in the theory’s…