Measurement of the azimuthal ordering of charged hadrons with the ATLAS detector

This paper presents a study of the possible ordering of charged hadrons in the azimuthal angle relative
to the beam axis in high-energy proton-proton collisions at the Large Hadron Collider (LHC). A spectral
analysis of correlations between longitudinal and transverse components of the momentum of the charged
hadrons, driven by the search for phenomena related to the structure of the QCD field, is performed. Data
were recorded with the ATLAS detector at center-of-mass energies of pffisffiffi ¼ 900 GeV and ffiffiffi ps ¼ 7 TeV.
The correlations measured in a kinematic region dominated by low-pT particles are not well described by
conventional models of hadron production. The measured spectra show features consistent with the
fragmentation of a QCD string represented by a helixlike ordered gluon chain.