How are anti quarks produced in $pp$ collision at LHC?

I remember reading that the background contains $q \bar{q}$ giving 4 leptons while studying the 4 lepton decay channel of Higgs boson. Since LHC is a $pp$ collider, I was wondering the source of anti-quark $\bar{q}$.

Or is it correct to say that both $q$ and $\bar{q}$ are produced simultaneously during collision?

• Z/$\gamma$ -> q-qbar, W$\pm$ -> q-q'bar, etc – JamieBondi Mar 12 '17 at 4:35
• The proton itself, apart from the quark content uud, has a lot of virtual q-qbar pairs and gluons propagating in the proton. – JamieBondi Mar 12 '17 at 4:43
• @JamieBondi So can I say that there are virtual mesons present in a proton? – kg__ Mar 12 '17 at 4:50
• Virtual quarks wouldn't form mesons/baryons. They are very energetic (in QFT jargon, they are off-shell). The coupling strength of QCD is small at high energies, so virtual quarks won't bind into bound states. – JamieBondi Mar 12 '17 at 5:00
• It is indeed correct to say that both $q$ and $\overline{q}$ are produced during collisions. They must be produced in equal numbers to conserve baryon number. – dukwon Mar 12 '17 at 10:16