COEPP-MN-16-6
MCNET-16-06
arXiv:1603.05298
Eur.Phys.J. C76 (2016) 299

by: Martin, Tim (Warwick U.) et al.

Abstract:
We define a new set of observables to probe the structure of the underlying event in hadron collisions. We use the conventional definition of the “transverse region” in jet events and, for a fixed window in jet $p_\perp$ , propose to measure several discriminating quantities as a function of the level of activity in the transverse region. The measurement of these observables in LHC data would reveal whether, e.g., the properties of “low-UE” events are compatible with equivalent measurements in $e^+e^-$ collisions (jet universality), and whether the scaling behaviour towards “high-UE” events exhibits properties of non-trivial soft-QCD dynamics, such as colour reconnections or other collective phenomena. We illustrate at $\sqrt{s} = 13 \,\mathrm{{TeV}}$ that significant discriminatory power is obtained in comparisons between MC models with varying treatments of collective effects, including Pythia 8, epos, and Dipsy.