# Pair production of quarks

I was reading about pair-production of particles by photons, and in every place that I read, only the electron/positron production was said. So I had the following doubt, is it possible to have a quark/anti-quark pair production? if yes, how?

• Sure, at the level of a feynman diagram, an electron and positron say can annihilate to produce a quark, antiquark pair. Of course the experimental signature is realised as a pair of jets. – CAF Jul 4 '16 at 14:34

## 1 Answer

Yes, pair production is possible for quarks in the same way that for electrons or muons. But there are two caveats:

• QCD has a nasty property called confinement: quarks themselves can't exist isolated in nature, they must be inside a meson or baryon. In fact, they usually produce jets of such particles.
• Electrons are much lighter than quarks, and of course, mesons. To produce an electron-positron pair, you need a photon with at least 1.022 MeV, while the production of a pion pair needs a photon of around 300 MeV.

There are experiments of pion pair productions both in scattering of one photon and one proton [1] and scattering of two photons [2].

[1] M. Ripani et al.: Pion-pair production on a proton by photons in the energy region of nucleon-resonance excitation. (Link, behind paywall)

[2] A. E. Blinov et al.: Pion pair production in photon-photon collisions. (Link, behind paywall)

• Thanks, but now i have a new doubt, when the quark/anti-quark pair is produced, they glue togheter as a meson or new quarks/anti-quarks are produced for this pair? – jfinizolas Jul 4 '16 at 15:53