Today In Science History – November 24 – W and Z Bosons

Simon van der Meer
Simon van der Meer (1925 – 2011)

November 24 is Simon van der Meer’s birthday. He was a Dutch physicist who, together with Carlo Rubbia, first detected the existence of W and Z particles during a series of experiments at the CERN Super Proton Synchrotron in 1983. Their discovery confirmed the electroweak theory of subatomic particles that unify the electromagnetic force and weak nuclear force. They are also important to the Standard Model of particle physics.

W and Z particles are the carriers of the weak nuclear force, one of the four fundamental forces of physics. The W particles carry a charge of either +1 or -1 and the Z particle carries no charge. They are massive particles, approximately 100 times the mass of a proton, but have a half-life of only 3 x 10-25 seconds. They are typically present when beta nuclear decay occurs. During β decay, one of the down quarks in the neutron becomes an up quark, turning the neutron into a proton and emits a W particle. The W particle quickly decays and produces an electron (beta particle) and an anti-neutrino.

The discovery of W and Z bosons would earn both men the 1984 Nobel Prize in Physics. Van der Meer’s largest contribution was to the discovery of the technique of stochastic cooling of particle beams. This process uses electric fields to keep the individual particles of a beam close together. This effectively lowers the entropy of the beam system or ‘cools’ the beam. This focusing of the beams allows accelerators to greatly increase the overall kinetic energy of the particles. This increase was enough to bring the proton and anti-proton beams at CERN to enough energy to produce W and Z protons when the beams collided with each other.

Notable Science History Events for November 24

1926 – Tsung Dao Lee was born.

Tsung Dao Lee
Tsung Dao Lee.
Brookhaven National Laboratory

Lee is a Chinese-American physicist who shares the 1957 Nobel Prize in Physics with Chen Ning Yang for their investigations into parity laws and discoveries relating to elementary particles. They discovered violations in the parity conservation in elementary particle physics and showed the theta-meson and tau-mesons were both the same particle, a K-meson.

1925 – Simon van der Meer was born.

1876 – Hideyo Noguchi was born.

Hideyo Noguchi
Hideyo Noguchi (1876 – 1928)

Noguchi was a Japanese bacteriologist who discovered the bacteria Treponema pallidum is the cause of syphilis. He discovered the bacterium in the brains of people who had died of paresis. He was also working on the cause of yellow fever when he contracted the disease and died.

1859 – Darwin’s “On the Origin of Species” was published

Origin of Species Title Page
Origin of Species Title Page

Darwin’s “On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life” was first published. The title would be later shortened to the more known “Origin of Species”. This work is considered the beginning of evolutionary biology.