2017/08/31 by R. Gauld, A. Gehrmann–De Ridder, A. Gehrmann-De Ridder +4
Physics and Astronomy · #Algorithm #Computer science #High-Energy Particle Collisions Research #Large Hadron Collider #Lepton #Nuclear physics #Particle physics #Particle physics theoretical and experimental studies #Physics #Quantum Chromodynamics and Particle Interactions #Quantum chromodynamics #hep-ex #hep-ph
paper · pdf · doi:10.1007/jhep11(2017)003
21 pages + refs, 13 figures. v2 reflects published JHEP version. Includes the evaluation of uncorrelated scale uncertainties when computing the angular coefficients. Plots and text updated accordingly
openalex publication_date 2017/11/01 · arxiv created 2017/11/02 · arxiv updated 2017/12/06 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
A bstract The angular distributions of lepton pairs in the Drell-Yan process can provide rich information on the underlying QCD production mechanisms. These dynamics can be parameterised in terms of a set of frame dependent angular coefficients, A i=0,…,7 , which depend on the invariant mass, transverse momentum, and rapidity of the lepton pair. Motivated by recent measurements of these coefficients by ATLAS and CMS, and in particular by the apparent violation of the Lam-Tung relation A 0 − A 2 = 0, we perform a precision study of the angular coefficients at O(αs3) <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>O</mml:mi> <mml:mfenced> <mml:msubsup> <mml:mi>α</mml:mi> <mml:mi>s</mml:mi> <mml:mn>3</mml:mn> </mml:msubsup> </mml:mfenced> </mml:math> in perturbative QCD. We make predic-tions relevant for pp collisions at √(s)=8 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> <mml:mo>=</mml:mo> <mml:mn>8</mml:mn> </mml:math> TeV, and perform comparisons with the available ATLAS and CMS data as well as providing predictions for a prospective measurement at LHCb. To expose the violation of the Lam-Tung relationship we propose a new observable Δ LT = 1 − A 2 /A 0 that is more sensitive to the dynamics in the region where A 0 and A 2 are both small. We find that the O(αs3) <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>O</mml:mi> <mml:mfenced> <mml:msubsup> <mml:mi>α</mml:mi> <mml:mi>s</mml:mi> <mml:mn>3</mml:mn> </mml:msubsup> </mml:mfenced> </mml:math> corrections have an important impact on the p T,Z distributions for several of the angular coefficients, and are essential to provide an adequate description of the data. The compatibility of the available ATLAS and CMS data is reassessed by performing a partial χ 2 test with respect to the central theoretical prediction which shows that χ 2 /N data is significantly reduced by going from O(αs2) <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>O</mml:mi> <mml:mfenced> <mml:msubsup> <mml:mi>α</mml:mi> <mml:mi>s</mml:mi> <mml:mn>2</mml:mn> </mml:msubsup> </mml:mfenced> </mml:math> to O(αs3) <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>O</mml:mi> <mml:mfenced> <mml:msubsup> <mml:mi>α</mml:mi> <mml:mi>s</mml:mi> <mml:mn>3</mml:mn> </mml:msubsup> </mml:mfenced> </mml:math> .