2 Tweak edited May 10 '16 at 17:13 John Rennie 286k4545 gold badges584584 silver badges833833 bronze badges The notation $$pp \rightarrow t\bar{t}$$ doesn't literally mean the two protons disappear leaving just a top and antitop. It means a top and antitop are created as well as a shower of other debris. Because protons are composite objects a 13TeV proton-proton collision is an exceedingly messy business. At that energy the quarks are resolved so it's really a quark-quark collision with the other contents of the proton more or less involved. As the reaction products leave the site of the collision the QCD binding energy produces a whole mess of particles. The dominant process for top-antitop production of the LHC is from two gluons i.e. $$gg \rightarrow t\bar{t}$$. The calculation of the $$pp \rightarrow t\bar{t}$$ probability is the probability that the debris includes a top-antitop pair.   Likewise for the other reactions listed on that page. The notation $$pp \rightarrow t\bar{t}$$ doesn't literally mean the two protons disappear leaving just a top and antitop. It means a top and antitop are created as well as a shower of other debris. Because protons are composite objects a 13TeV proton-proton collision is an exceedingly messy business. At that energy the quarks are resolved so it's really a quark-quark collision with the other contents of the proton more or less involved. As the reaction products leave the site of the collision the QCD binding energy produces a whole mess of particles. The calculation of the $$pp \rightarrow t\bar{t}$$ probability is the probability that the debris includes a top-antitop pair.   Likewise for the other reactions listed on that page. The notation $$pp \rightarrow t\bar{t}$$ doesn't literally mean the two protons disappear leaving just a top and antitop. It means a top and antitop are created as well as a shower of other debris. Because protons are composite objects a 13TeV proton-proton collision is an exceedingly messy business. At that energy the quarks are resolved so it's really a quark-quark collision with the other contents of the proton more or less involved. As the reaction products leave the site of the collision the QCD binding energy produces a whole mess of particles. The dominant process for top-antitop production of the LHC is from two gluons i.e. $$gg \rightarrow t\bar{t}$$. The calculation of the $$pp \rightarrow t\bar{t}$$ probability is the probability that the debris includes a top-antitop pair. Likewise for the other reactions listed on that page. 1 answered May 10 '16 at 17:00 John Rennie 286k4545 gold badges584584 silver badges833833 bronze badges The notation $$pp \rightarrow t\bar{t}$$ doesn't literally mean the two protons disappear leaving just a top and antitop. It means a top and antitop are created as well as a shower of other debris. Because protons are composite objects a 13TeV proton-proton collision is an exceedingly messy business. At that energy the quarks are resolved so it's really a quark-quark collision with the other contents of the proton more or less involved. As the reaction products leave the site of the collision the QCD binding energy produces a whole mess of particles. The calculation of the $$pp \rightarrow t\bar{t}$$ probability is the probability that the debris includes a top-antitop pair. Likewise for the other reactions listed on that page.