2015/12/16 by C. Adolph, Adolph, C., M. Aghasyan +453
Physics and Astronomy · #FOS: Physical sciences #High Energy Physics - Experiment (hep-ex) #High Energy Physics - Phenomenology (hep-ph) #High-Energy Particle Collisions Research #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions #hep-ex #hep-ph
paper · pdf · doi:10.48550/arxiv.1512.05053
14 pages, 6 figures
openalex publication_date 2015/12/16 · arxiv created 2017/02/22 · arxiv updated 2017/02/23 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Using a novel analysis technique, the gluon polarisation in the nucleon is re-evaluated using the longitudinal double-spin asymmetry measured in the cross section of semi-inclusive single-hadron muoproduction with photon virtuality Q2>1~(\rm GeV/c)2. The data were obtained by the COMPASS experiment at CERN using a 160 GeV/c polarised muon beam impinging on a polarised 6LiD target. By analysing the full range in hadron transverse momentum p\rm T, the different p\rm T-dependences of the underlying processes are separated using a neural-network approach. In the absence of pQCD calculations at next-to-leading order in the selected kinematic domain, the gluon polarisation Δg/g is evaluated at leading order in pQCD at a hard scale of μ2= ⟨ Q2 ⟩ = 3 (\rm GeV/c)2. It is determined in three intervals of the nucleon momentum fraction carried by gluons, x\rm g, covering the range 0.04 < x \rm g < 0.28~ and does not exhibit a significant dependence on x\rm g. The average over the three intervals, ⟨ Δg/g ⟩ = 0.113 ± 0.038\rm (stat.)± 0.036\rm (syst.) at ⟨ x\rm g ⟩ ≈ 0.10, suggests that the gluon polarisation is positive in the measured x\rm g range.