QCD measurements at the Tevatron

TL;DR

This paper presents a comprehensive set of QCD measurements at the Tevatron collider, testing theoretical predictions, constraining parton distribution functions, and exploring multiple parton interactions, with implications for understanding strong interactions.

Contribution

It provides new experimental data and analyses that test and refine perturbative QCD calculations, parton distribution functions, and models of multiple parton interactions at Tevatron energies.

Findings

Precise measurement of alpha_s(m_Z) = 0.1161^{+0.0041}_{-0.0048}

Discrepancies in low-energy photon production with NLO pQCD

Determination of sigma_eff = 16.4+- 2.3 mb for MPI

Abstract

Selected quantum chromodynamics (QCD) measurements performed at the Fermilab Run II Tevatron ppbar collider running at sqrt{s} = 1.96 TeV by CDF and D0 Collaborations are presented. The inclusive jet, dijet production and three-jet cross section measurements are used to test perturbative QCD calculations, constrain parton distribution function (PDF) determinations, and extract a precise value of the strong coupling constant, alpha_s(m_Z) = 0.1161^{+0.0041}_{-0.0048}. Inclusive photon production cross-section measurements reveal an inability of next-to-leading-order (NLO) perturbative QCD (pQCD) calculations to describe low-energy photons arising directly in the hard scatter. The diphoton production cross-sections check the validity of the NLO pQCD predictions, soft-gluon resummation methods implemented in theoretical calculations, and contributions from the parton-to-photon fragmentation diagrams. Events with W/Z+jets productions are used to measure many kinematic distributions allowing extensive tests and tunes of predictions from pQCD NLO and Monte-Carlo event generators. The charged-particle transverse momenta (pT) and multiplicity distributions in the inclusive minimum bias events are used to tune non-perturbative QCD models, including those describing the multiple parton interactions (MPI). Events with inclusive production of photon and 2 or 3 jets are used to study increasingly important MPI phenomenon at high pT, measure an effective interaction cross section, sigma_eff = 16.4+- 2.3 mb, and limit existing MPI models.