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At high energies, the strong interactions between two hadrons can be factorized into three components: (a) the probability of finding the partons in the hadrons, (b) the in- teraction between quasi-free partons, and (c) fragmentation and hadronization of the final state partons. The process is schematically shown in Figure 1. The cross section of the hadron-hadron scattering with 4-momenta P$_{1}$ and P$_{2}$ can be written as [13] : 

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The hard interaction between partons i, j is given by ˆ σ$_{ij}$ where p$_{1}$ = x$_{1}$P$_{1}$ and p$_{2}$ = x$_{2}$P$_{2}$ are 4-momenta of the two partons. It is independent of the incoming hadrons’ structure and can be calculated using pQCD. The function f$_{i}$ ( x, µ 2 $_{F}$) is the probability of finding a parton i with momentum fraction x at the scale µ$_{F}$ , and is called the parton distribution function PDF. The sum i, j is over the partons in the two respective hadrons. α$_{s}$ is the strong coupling constant. µ$_{R}$ is the renormalization scale, which is used to remove non-physical 

