Azimuthal particle correlations as a probe of collectivity in deep inelastic ep collisions at HERA

Abstract

Measurements of two-particle azimuthal correlations, c_n{2}, where n = 1–4 denotes the harmonics, are presented for neutral current deep inelastic ep scattering events, collected with the photon virtuality, Q^2 , above 5 GeV^2 with the ZEUS detector at HERA at a centre-of-mass energy, s, of s = 318 GeV. The c_n{2} were determined for charged particles with laboratory pseudo-rapidities, η, in the range −1.5 < η < 2 and transverse momenta, p_T , in the range 0.1 < p_T < 5.0 GeV/c. Distributions are presented as functions of the event multiplicity, N_ch, the separations in pseudorapidity, ∆η, and the separation in p_T, ∆p_T . The data do not provide evidence for any collective effects.