WIDG Seminar: Youqi Song, Yale, “Probing parton shower and hadronization with jet substructure measurements in pp collisions at STAR”

Jets are collimated sprays of final-state particles produced from initial high-momentum-transfer partonic scatterings in particle collisions. Since jets are multi-scale objects that connect asymptotically free partons to confined hadrons, jet substructure measurements can provide insight into parton evolution and the ensuing hadronization processes. In addition to the inclusive jet and the SoftDrop groomed jet observables, such as the jet mass (M), jet charge (Q), groomed jet mass (Mg), the groomed jet radius (Rg) and shared momentum fraction (zg), the STAR collaboration has also recently measured the correlations between various substructure observables, including the zg distributions for different Rg selections and for different number of splittings along the jet shower. We continue our exploration of multi-dimensional jet substructure observables, measuring a newly proposed observable, the CollinearDrop groomed jet mass, while also utilizing a novel machine learning method, MultiFold, to correct for detector effects.
The interplay between different stages of the parton shower can be probed with the correlation between SoftDrop and CollinearDrop groomed jet observables, the latter of which have an enhanced sensitivity to the soft radiation within jets. In this talk, I will first give an overview of the recent jet substructure measurements at STAR, and then present the first measurement of CollinearDrop jet mass and its correlation with SoftDrop groomed jet observables, such as Rg and zg. These observables are fully corrected for detector effects with MultiFold, which preserves the correlations in the multi-dimensional observable phase space, and is therefore ideal for such correlation measurements.