## Leo Bellantoni

#### Light, heavy light and asymmetry

DZero measures the weak mixing angle using the decay of a Z boson into two muons.

#### The most you can know

What is the matrix element, and why is it useful for measuring the top quark?

#### Matter and antimatter

Antimatter in the universe is extremely rare; the universe is made pretty much entirely out of matter. DZero digs deeper into a previous, unusual result measuring the difference between matter and antimatter.

#### Turn to the left, turn to the right!

DZero measured the average direction of spins in top pairs produced at the Tevatron using its full data set.

#### Theta and Tau, two generations later

The Bs0 meson is a superposition of two different possibilities, called CP-even and CP-odd. Does one case decay more slowly than the other?

#### When barns collide

Protons have parts that, as mentioned in previous columns, have the not terribly imaginative name of “partons.”

#### Hadron assembly instructions

Determining the precise details of how the strong nuclear force assembles quarks into hadrons is not always easy. Disponible en español Method A: 3 quarks chromodynamic glue Step 1. Glue the quarks together. Step 2. Voila! Method A will produce a baryon; most of your more massive hadrons are baryons. The type of baryon will be determined in part by the flavor of the quarks used and how the quarks are aligned. For example, if you have glued together one…

#### The directionless universe

The formation of a snowflake or indeed of any crystal spontaneously breaks directional symmetry through the formation of specific special directions. Photo: Wilson Bentley Disponible en español A body in uniform motion tends to stay in uniform motion unless acted upon by outside forces, right? Right. And does it matter which direction the motion is in? Nope. There is no special direction in the universe. A Boeing 747 accelerating at 1.5 meters per second per second will be moving fast…

#### Measure thrice, theorize once

This shows the production of a top-antitop pair decaying in the dilepton channel. In this case the top quark decays into an antimuon, and the antitop decays into an electron. Disponible en español One of the very fundamental but unpredictable numbers in the Standard Model is the mass of the top quark. Like the strength of gravity, it is one of those numbers that has no explanation and yet is crucially linked to the kind of universe we live in….

#### From E-8 to E-823

Data from five very different experiments over a wide range of energies and taken over a span of four decades fall together on a smooth curve here. When the trajectory of the outgoing Λ or anti-Λ is close to the trajectory of the incoming proton (the left side of the plot), there are relatively few anti-Λ produced. On the right, when the outgoing trajectory is very different from the incoming one, Λ and anti-Λ are produced at the same rate….