List all parton processes, in addition to those shown in...

List all parton processes, in addition to those shown in Fig. 11.13, that can contribute to reaction (c) to the same order of $\alpha_s$. Comment on the relative strengths of the subprocesses, comparing, in particular, pp- and pp-initiated reactions.

Key Concepts

Parton Distribution Functions (PDFs)

PDFs quantify the probability of finding a given parton carrying a specific fraction of the parent hadron's momentum. They play a central role in connecting the parton-level calculations to the actual hadronic collision experiments, and variations in PDFs between different hadrons (or between protons and antiprotons) are key to understanding differences in reaction dynamics.

Collision Initiation Differences (pp vs p?p)

The nature of the initiating particles (proton-proton versus proton-antiproton) affects the accessible parton configurations due to differences in parton distribution functions (PDFs) and the inherent particle–antiparticle content. This leads to variations in the relative strengths of subprocesses, influencing the overall reaction rates and observable final states.

Perturbative QCD and Order in ?s

Perturbative QCD is the framework used to calculate strong interaction processes using a series expansion in the strong coupling constant, ?s. 'Same order of ?s' means that only those parton-level processes that contribute at a given power of ?s are considered. This ensures that the comparison is made among processes of equivalent perturbative accuracy.

Subprocess Contributions and Feynman Diagrams

In analyzing a reaction, each parton subprocess represented by a Feynman diagram contributes to the total cross section. Identifying all subprocesses that contribute to a particular order of ?s is essential to obtain a complete picture of the reaction dynamics, including interference effects and relative contributions from different channels.

Parton Processes

These are the elementary interactions between quarks and gluons that occur during high-energy collisions. In the context of quantum chromodynamics (QCD), parton processes describe how partons (the constituents of hadrons) scatter or interact, and they are typically represented by Feynman diagrams. Their analysis is crucial for understanding the underlying dynamics of hadronic reactions.

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