Lin Chen
Phenomenology in High-Energy Physics
Supervisor: Lin Chen (email, inspirehep)
This project cluster offers a guided introduction to key techniques in theoretical and phenomenological studies of high-energy collisions.
Students will explore the dynamics of particle interactions in both elementary and nuclear processes, ranging from analytical calculations to numerical simulations.
They can choose from one of four distinct sub-projects, focusing either on pen-and-paper derivations or hands-on computational work.
Each sub-project is adapted from a typical MSc-level exercise and is designed to be accessible to highly motivated undergraduate students.
P1 (analytical) - NLO Corrections to Pair Production
Introduction:
This project introduces students to loop corrections in Quantum Field Theory (QFT).
Focusing on the simplest QED process: electron-positron annihilation into a muon pair, students will analyze both the Leading-Order (LO) Feynman diagram and its Next-to-Leading-Order (NLO) correction with photon radiation.
The aim is to develop familiarity with tree- and loop-level calculations, understand the origin of singularities, and apply techniques to handle divergences.
Expected outcomes:
- Understanding of Feynman diagram rules and their application to QED processes
- Tree-level and one-loop calculations for e⁺e⁻ → μ⁺μ⁻
- Cross-section computation and application of dimensional regularization
- Optional: determination of the tau lepton mass from cross-section ratios
- Optional: estimation of Nc from the ratio of hadronic to leptonic cross-sections
Requirements:
- Familiarity with special relativity and quantum mechanics
- Basic calculus skills
P2 (analytical) - Opacity Expansion in Parton Energy Loss
Introduction:
This project explores the foundational aspects of jet quenching through the Gyulassy-Levai-Vitev (GLV) formalism.
Beginning with a review of Feynman rules and basic concepts in heavy-ion collisions, students will focus on computing the first-order opacity contribution to the medium-induced gluon radiation spectrum in a hot QCD plasma.
The emphasis is on analytical derivations, with attention to diagrammatic summation techniques and approximations used in perturbative QCD.
Expected outcomes:
- Understanding the conceptual basis of jet quenching in a quark-gluon plasma
- Application of Feynman diagrams to model jet–medium scattering processes
- Derivation of the Leading-Order (first-opacity) contribution to induced gluon radiation
- Optional: Study of detailed balance using basic thermal field theory techniques
- Optional: Extension to higher-order terms in the opacity expansion
Requirements:
- Familiarity with Feynman diagrammatics
- Basic calculus skills
P3 (computational) - Dijet Cross-Sections at Leading-Order
Introduction:
This hands-on computational project introduces students to the numerical calculation of cross-sections for physically relevant processes.
Students will implement tree-level 2→2 partonic scattering leading to dijet production, and compute differential cross-sections to be compared with experimental data from the LHC.
This project serves as an entry point into collider phenomenology, linking theoretical calculations with measurable observables.
Expected outcomes:
- Familiarity with numerical integration techniques
- Implementation of Leading-Order matrix elements for dijet production in proton–proton collisions
- Calculation and analysis of differential cross-sections with comparison to experimental data
- Optional: Extension to beyond LO corrections
- Optional: Application to heavy-ion collisions via simple quenching models
Requirements:
- Basic familiarity with collider physics concepts
- Programming experience and elementary numerical analysis skills
P4 (computational) - Glauber Modelling in Nuclear Collisions
Introduction:
This project introduces the classical Glauber model, used to characterize the initial geometry of nuclear collisions.
Students will implement both optical and Monte Carlo versions of the model to compute geometric observables such as participant numbers and spatial eccentricities, which are essential for centrality classification and anisotropic flow studies in heavy-ion collisions.
Expected outcomes:
- Familiarity with nuclear collision geometry and numerical integration techniques
- Implementation of optical and Monte Carlo Glauber models
- Optional: Calculation of eccentricities in non-central collisions
- Optional: Mapping of impact parameter to centrality classes
Requirements:
- Basic familiarity with collider or nuclear physics concepts
- Programming experience and elementary numerical analysis skills