Measurement of inclusive two-particle angular correlations in pp collisions with the ATLAS detector at the LHC

TL;DR

This paper reports on the measurement of two-particle angular correlations in proton-proton collisions at 900 GeV and 7 TeV using the ATLAS detector, revealing complex structures not well modeled by existing simulations.

Contribution

First measurement of two-particle angular correlations in pp collisions at these energies with detailed comparison to multiple Monte Carlo models.

Findings

Complex correlation structures observed at both energies

Existing models do not adequately describe the data

Provides new data for tuning particle collision models

Abstract

We present a measurement of two-particle angular correlations in proton-proton collisions at sqrt(s) = 900 GeV and 7 TeV. The collision events were collected during 2009 and 2010 with the ATLAS detector at the Large Hadron Collider using a single-arm minimum bias trigger. Correlations are measured for charged particles produced in the kinematic range of transverse momentum pT > 100 MeV and pseudorapidity |eta| < 2.5. A complex structure in pseudorapidity and azimuth is observed at both collision energies. Results are compared to Pythia 8 and Herwig++ as well as to the AMBT2B, DW and Perugia 2011 tunes of Pythia 6. The data are not satisfactorily described by any of these models.