Bubble chamber picture of decay of a Xi0 to a lambda0 and a pi0

The first highlighted track shows the trajectory of the from the decay of an omegaminus . This then decays into a and a . The lambda decays to a proton and a in a characteristic vee; the decays to two photons which (against the odds) both produce e+e- pairs in the hydrogen.

Victor Weisskopf, the ex-Director General of CERN, used to joke by showing a blank sheet of paper and calling it a bubble chamber picture of a decaying to a and a – neutral particles are not supposed to leave traces in a bubble chamber!

For details of the important picture – the discovery of the omega- click here.