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AI for Particle Physics
Published in Volker Knecht, AI for Physics, 2023
Mario Campanelli, Volker Knecht
Hadronic jets are collimated sprays of particles produced by the formation of hadrons out of quarks and gluons denoted as hadronization. Due to the laws of strong interactions, particles with a color charge (the property leading to strong interactions) cannot live in isolation. At high energies, quarks will radiate gluons, which will produce quark–antiquark or gluon–antigluon pairs, in a process called parton shower. At lower energies, quarks will pick up other quark-antiquark pairs from the vacuum to produce more stable hadrons like pions, kaons, protons, and neutrons, which is what is called hadronization. When the initial quarks or gluons have sufficiently large momenta, the resulting hadrons will be collimated and all emitted in a narrow geometrical cone, the hadronic jet. Its axis, defined by the weighted average of the directions of the particles composing it, is a proxy for the direction of the quark or gluon that created it, and the jet transverse momentum a proxy for that of the initial particle. Defining which particles belong to a jet is not a trivial task, especially in situations where there are several nearby. Several jet clustering algorithms have been developed to, for instance, remove detector noise or calibrate the jets.
Comparison of Rutherford’s atomic model with the Standard Model of particle physics and other models
Published in Journal of the Royal Society of New Zealand, 2021
The Standard Model was originally constructed to account for the particles that had been found by the 1960s, and it did a relatively good (but not perfect) job in this regard. It was furthermore shown, under various assumptions, to explain a large body of high-energy scattering data, but the underlying assumptions were not clearly explained. For example, in interactions of electrons with protons, it was assumed that the electron interacts with quarks contained in the proton as if the quarks were free particles. Final-state interactions between quarks were then assumed to occur in a process known as ‘hadronization’ that produced outgoing jets of integrally charged hadrons, but the interactions that caused this were not fully explained. This was the case originally (Feynman 1972), and it remains the case today (Agostini et al. 2020; Section 1.1.1). In addition, low-energy phenomena of nuclear physics have generally remained outside the model (Ishi et al. 2007; Doi et al. 2017). It has not been shown, for instance, how the geometrical arrangement from the Rutherford era shown in Figure 2 might arise in the Standard Model.