Double parton scattering (DPS) is the process in which one has two hard scatterings in an individual proton-proton collision. This process is interesting to study both from the point of view of improving our understanding of proton structure, and improving our modelling of multiple scattering backgrounds to single scattering processes. This talk will focus on DPS in the same-sign WW process, a long-studied 'golden channel' to study DPS. We will begin with a basic overview of how DPS is currently modelled, starting with the crude 'DPS pocket formula' approach that neglects correlations between the partons. We will describe the modelling of DPS in various Monte Carlo simulation codes, including Herwig, Pythia, and the dedicated DPS parton shower, dShower, explaining the features beyond the pocket formula in each. We will then summarise the recent measurement of same-sign WW by CMS, discussing the backgrounds involved, the approach needed to extract the DPS signal, and the predictions from the various Monte Carlo codes. Finally we will discuss the prospects for using same-sign WW (and possibly other processes) at the HL-LHC to probe correlations between partons in the proton beyond the pocket formula.
Jo Gaunt is a Royal Society University Research Fellow at the University of Manchester, and is interested in various aspects of QCD theory, including the theory of multiple parton scattering, factorisation, resummation and higher order calculations. He did his PhD on "Double parton scattering in proton-proton collisions" under James Stirling, then had PDRA positions at DESY Hamburg, Nikhef and CERN before starting in Manchester. He is an editor of the book "Multiple Parton Interactions at the LHC" published in 2018, and in 2020 was awarded the Guido Altarelli award for his work on the theory and phenomenology of multiple scattering.
Ankita Mehta is an experimentalist working on the CMS experiment with research interests pertaining to the SM physics measurements, EFT approaches for new physics searches and muon detectors. She started working on the same-sign WW production via double-parton scattering at 8TeV during her PhD at Panjab University, India followed by analysis with Run2 datasets while working for ELTE and UHH as a postdoctoral researcher. The observation of same-sign WW production via DPS was reported by CMS in 2022. Recently, she joined CERN as a fellow and exploring projects in the top physics sector. She is a L3 convener of the SMP multi boson subgroup since 2022.