Read the paper: QCD-10-037
This paper extends CMS’s previous measurements of the production rates of isolated prompt photons. The production rates agree with the predictions of perturbative Quantum Chromodynamics (pQCD), although, at low transverse energies, the predictions tend to be higher than the measured values.
Prompt photons are produced in the interactions of the partons present within the particles colliding at the LHC, and don't come from the decay of mesons or hadrons. Measuring the production rates of isolated prompt photons in proton collisions is important for three reasons:
- It forms a test for the theory of pQCD.
- It serves as a reference for similar measurements in heavy-ion collisions.
- It is a key background in the searches for new phenomena, including searches for the Higgs boson.