Dijet production, collision centrality and backgrounds in high-energy p-p collisions

TL;DR

This paper investigates the relationship between jet production, underlying event characteristics, and collision centrality in high-energy proton-proton collisions, using a two-component model to analyze data and predict particle distributions.

Contribution

It introduces a detailed analysis of the underlying event and its relation to jet production and centrality, challenging assumptions and proposing a universal jet contribution to transverse multiplicity.

Findings

The underlying event includes a significant contribution from the triggered dijet.

Proposed a universal large-angle jet contribution to transverse multiplicity.

PP centrality is not strongly controlled by the dijet trigger pT.

Abstract

Two aspects of high-energy \pp collisions share common phenomenological elements: (a) A correlation between jet production and \pp centrality is suggested by the transverse partonic structure of hadrons inferred from deep-inelastic scattering data. (b) The {\em underlying event} (UE) is defined as the final-state particles complementary to a triggered high-energy dijet. An observable common to both topics is variation of so-called {\em transverse multiplicity} $N_\perp$ with a $p_{t,trig}$ dijet trigger. We test assumptions associated with \pp collision centrality and the UE. We determine the nature of the UE and explore the relation between jet production and \pp centrality. We use the {\em two-component model} (TCM) of spectra and correlations derived from 200 GeV \pp collisions to construct a simulated particle distribution on $(p_t,n_{ch})$ to predict the $N_\perp$ response to $p_{t,trig}$. The $p_t$ spectrum TCM combined in this analysis with measured minimum-bias \pp angular correlations suggests that the UE includes a substantial contribution from the triggered dijet in addition to the contribution from projectile fragmentation (beam-beam remnants). The jet contribution to $N_\perp$ may represent a universal large-angle base common to all dijets that extends across $2\pi$ azimuth. The analysis further suggests that \pp centrality is not controlled significantly by $p_{t,trig}$ but may be correlated to some extent with an imposed $n_{ch}$ condition, depending on the role of fluctuations. Future correlation studies may better determine the role of \pp centrality. These results may have implications for ongoing RHIC analysis and LHC searches for physics beyond the standard model.