A trap for b quarks

25 March 1998

Display the high resolution version

This delicate cage of silicon is in effect a trap to catch particles containing the b quark, the second heaviest of the six quarks. Quarks are the basic building blocks of protons, neutrons and many other particles. However, no one has ever detected a quark on its own. Due to the nature of the strong force that acts upon them quarks always get together to form more complex particles (hadrons). The b quarks, discovered in 1976, can combine with other quarks to form so-called B-particles, but the B-particles decay very quickly - in around 10-12 s, or a million millionths of a second - so they are difficult to detect. The apparatus shown here (a "vertex detector") is designed to help identify B-particles produced when electrons and positrons collide at the heart of the Delphi experiment at CERN, Geneva. The main "barrel" section - about 50 cm long - consists of silicon detectors which provide accurate measurements (to 10 microns) of the tracks of particles produced in B-particle decays at the heart of the detector, 1 cm or less from the place where the electrons and positrons collide.

Credit: CERN / Delphi

Please contact person or institution named for information about permission for public or commercial use.