# What is the mass of a top quark?

## What is the mass of a top quark?

173 GeV/c2
The top quark is the most massive known fundamental particle to date (PDG). It is an up-type quark (charge +2/3e) in the 3rd family of elementary particles. Its mass is 173 GeV/c2.

How is quark mass measured?

Ultimate precision of the jet-energy calibration and the top-quark mass measurement is obtained by constraining the jet energies to match the expected W-boson mass, which is precisely known from previous measurements. From the likelihood fit, the top-quark mass is measured to be mtop=172.04±0.19 (stat.

### How was the top quark predicted?

The W bosons from top quark decays carry polarization from the parent particle, hence pose themselves as a unique probe to top polarization. In the Standard Model, the top quark is predicted to have a spin quantum number of 1⁄2 and electric charge + 2⁄3.

Does quark have mass?

Quarks have an astonishingly wide range of masses. The lightest is the up quark, which is 470 times lighter than a proton. The heaviest, the t quark, is 180 times heavier than a proton — or almost as heavy as an entire atom of lead. “So why these huge ratios between masses?

## Why is the top quark mass important?

The top-quark mass is a parameter of paramount importance in particle physics, playing a crucial role in the electroweak precision tests and in the stability of the Standard Model vacuum.

Do W bosons have mass?

The two (charged) W bosons each have a mass of about 80 GeV/c2 whereas the (neutral) Z boson has a mass of about 90 GeV/c2. In weak interactions, W and Z bosons interact with each other, as well as with all quarks and leptons.

### What quark has the least mass?

The up and down quarks are the most common and least massive quarks, being the constituents of protons and neutrons and thus of most ordinary matter.

When was the top quark found?

April 1995
April 1995: Discovery of the top quark at Fermilab. The Standard Model of particle physics holds that all matter is made from a small alphabet of elementary particles consisting of six quarks and six leptons.

## Why do W bosons have mass?

The quarks, leptons, and W and Z bosons moving around through space interact with this field, which is why these particles have mass. The photons and gluons do not interact with the Higgs field, which is why these particles do not have mass. It gives itself mass!

How are bosons detected?

Because the Higgs boson decays very quickly, particle detectors cannot detect it directly. Instead the detectors register all the decay products (the decay signature) and from the data the decay process is reconstructed.