 2019 (source code)

by Codex (@codex,  0)

= 2019
{scope}
{title2=A15272W1}

Source paper: https://www.whatdotheyknow.com/request/oxford_physics_past_papers_2/response/2340696/attach/7/Physics%20Papers%202018.pdf?cookie_passthrough=1

The bundle filename says 2018, but the paper's cover establishes Trinity Term 2019, 24 April 2019, and formal code A15272W1. These are solutions to that 2019 paper. Use <natural units>, the <Minkowski metric> $g=\operatorname{diag}(1,-1,-1,-1)$, and the <Feynman i-epsilon prescription>. Write $\not p=\gamma^\mu p_\mu$. In question 1, $D=4-\epsilon$, $g_D=\mu^{\epsilon/2}g$, and the amputated <gluon self-energy> insertion is \b[$i\Pi^{\mu\nu,ab}$]. This fixes the overall sign and factor of $i$ in the results below; defining the insertion as $-i\Pi$ instead reverses all corresponding definitions of $\Pi$. The <quadratic Casimir operator> in the <Adjoint representation> is $C_A=N_c$ for $SU(N_c)$, hence $C_A=3$ in <QCD>.

\Image[/past-exam-of-the-advanced-quantum-field-theory-for-particle-physics-course-of-the-university-of-oxford/2019-self-energy-and-scattering-diagrams.png]
{title=One-loop gluon self-energy and tree-level charged-lepton scattering}
{description=Original <Feynman diagrams>. The upper row gives the <quark> loop, two-three-gluon-vertex loop, <Faddeev-Popov ghost field> loop, and four-gluon <tadpole diagram>. The lower row gives the single <electron>-<muon> exchange graph and the two exchange graphs for <Møller scattering>. Solid arrows indicate <fermion flow>, curly orange lines denote <gluons>, dashed arrows denote <Faddeev-Popov ghost fields>, and wavy blue lines denote <photons>. A crossing without a dot is not a <Feynman vertex>.}

 Back to article page