Tonight, we return to my series on the Large Hadron Collider (LHC). I previously wrote about one very important property of a collider, its energy. Tonight, I write about another important property, luminosity. Dictionary definitions of luminosity typically refer to the presence of light or brightness; in other words, a luminous object is easy to see, such as something that is illuminated.
Conceptually, the term luminosity as used in particle physics also refers to ease of detecting something. In his book, Not Even Wrong (associated with a blog of the same name), Peter Woit states the following:
Besides the energy of its [particle] beams, the most important characteristic of any collider is its "luminosity." The luminosity of a collider is a measure of how many particles are in the beam and how small the interaction region is in which the beams coming from opposite directions are brought together inside a detector (p. 19).
The most layperson-friendly description of the units of luminosity I've been able to find is "collisions per square centimeter per second...", from this Berkeley Lab document.
Greater density of particles' concentration -- how many of them there are, in how small of an area -- thus would make them easier to detect. The LHC's luminosity is planned to be 10 to the 34th power (that's a lot of zeroes).
Increasing colliders' luminosities, however, is very difficult to do, as discussed by Woit and also in this Stanford Linear Accelerator Center (SLAC) document. The SLAC document also includes a graph that shows the luminosity levels for a number of colliders, including the LHC.
Luminosity is serious business. Major international conferences known as LUMI '06 and LUMI '05 have been held to track research developments in this area.