Study of quark and gluon jet substructure in Z+jet and dijet events from pp collisions

Abstract

Measurements of jet substructure describing the composition of quark- and gluon-initiated jets are presented. Proton-proton (pp) collision data at $$ \sqrt{s} $$ s = 13 TeV collected with the CMS detector are used, corresponding to an integrated luminosity of 35.9 fb−1. Generalized angularities are measured that characterize the jet substructure and distinguish quark- and gluon-initiated jets. These observables are sensitive to the distributions of transverse momenta and angular distances within a jet. The analysis is performed using a data sample of dijet events enriched in gluon-initiated jets, and, for the first time, a Z+jet event sample enriched in quark-initiated jets. The observables are measured in bins of jet transverse momentum, and as a function of the jet radius parameter. Each measurement is repeated applying a “soft drop” grooming procedure that removes soft and large angle radiation from the jet. Using these measurements, the ability of various models to describe jet substructure is assessed, showing a clear need for improvements in Monte Carlo generators.

Disentangling Quarks and Gluons with CMS Open Data

“…[3] and the unfolded CMS measurements from Ref. [71]. Binned distributions from these studies are available at HEPData [95,96], which is sufficient for the anchor bin method already implemented by ATLAS.…”

“…Because the absence of systematic uncertainties will be viewed as anathema to some readers (especially the authors of Refs. [3,71]), we want to explain more about our philosophy. We will leverage a full phase space unfolding strategy called OmniFold [21,22], which assigns each MC event a weight at the truth particle-level.…”

Event Generators for High-Energy Physics Experiments

“…For the Les Houches angularity [592,850,851], there is a major contribution in adding shifts in the angularity bins to the perturbative distribution, and a minor but significant effect of adding contributions from neighboring p T bins, which saturates when adding contributions from regions further away in p T . Figure 3 (right) shows the final prediction obtained after folding the resummed, perturbative, predictions with these corrections (red solid line) in comparison to data obtained by the CMS experiment [852]. Additionally, the result of a full fledged SHERPA simulation at MC@NLO level is displayed.…”

Phenomenology of jet angularities at the LHC

“…Physics observables measured on SoftDrop jets have been shown to be less affected by non-perturbative corrections and to be amenable to precision calculations in QCD [22][23][24][25][26][27]. This has triggered the attention of the jet substructure community, both theorists and experimentalists [28][29][30], over the past few years.…”

“…These observables, and closely related ones, have hence been studied in a variety of theoretical frameworks [40,[42][43][44][45][46][47][48][49][50][51][52]. Recent measurements of jet angularities at the LHC have for example been presented in [30,[53][54][55].…”