Multiple Parton Interactions, top--antitop and W+4j production at the LHC

TL;DR

This paper investigates the impact of Multiple Parton Interactions (MPI) on top-antitop and W+4j production at the LHC, highlighting their significance and potential for detailed study despite being a background to key processes.

Contribution

It provides the first detailed analysis of MPI effects on top-antitop and W+4j production at the LHC, including the potential to study Triple Parton Interactions.

Findings

MPI background to top-antitop is about 20% of W+4j background

MPI contributions can be separated from single interactions using angular resolution

Triple Parton Interactions may be detectable at the LHC

Abstract

The expected rate for Multiple Parton Interactions (MPI) at the LHC is large. This requires an estimate of their impact on all measurement foreseen at the LHC while opening unprecendented opportunities for a detailed study of these phenomena. In this paper we examine the MPI background to top-antitop production, in the semileptonic channel, in the early phase of data taking when the full power of $b$--tagging will not be available. The MPI background turns out to be small but non negligible, of the order of 20% of the background provided by W+4j production through a Single Parton Interaction. We then analyze the possibility of studying Multiple Parton Interactions in the W+4j channel, a far more complicated setting than the reactions examined at lower energies. The MPI contribution turns out to be dominated by final states with two energetic jets which balance in transverse momentum, and it appears possible, thanks to the good angular resolution of ATLAS and CMS, to separate the Multiple Parton Interactions contribution from Single Parton Interaction processes. The large cross section for two jet production suggests that also Triple Parton Interactions (TPI) could provide a non negligible contribution. Our preliminary analysis suggests that it might be indeed possible to investigate TPI at the LHC.