The coffee-time challenge

The challenge to identify the LEP events displayed on coffee tables in Restaurant 1 (Bulletin 02-03/2010) sparked interest among readers who do not have the opportunity to see them .



We have therefore decided to open the challenge to these readers by displaying the events on the web. We are also extending the deadline accordingly to 2 March.

There are 16 events in total (in two areas), four from each of the four LEP experiments, and they include examples of different particle decays observed at LEP during its 11 years of operation. The list below indicates the decay channels represented.

We are offering a prize of the ATLAS pop-up book, Voyage to the Heart of Matter, for the correct identification of all 16 events.  Entries should indicate the table number corresponding to each of the decays listed.

There will be a draw on 3 March to pick the winner from entries that correctly identify all 16 events.

Please email your answers to

Z → e+e- WW → eυμυ
Z → μ+μ- WW → μυμυ
Z → τ+τ- WW → τυτυ
Z → quark-antiquark WW → τυμυ
Z → quark-antiquark-gluon WW → quark-antiquark μυ
ZZ → e+e-μ+μ- WW → quark-antiquark eυ
ZZ → quark-antiquark e+e- WW → quark-antiquark τυ
ZZ → quark-antiquark μ+μ- WW → quark-antiquark quark-antiquark


by CERN Bulletin