Exploring jet substructure in semi-visible jets

Semi-visible jets arise in strongly interacting dark sectors, where parton evolution includes dark sector emissions, resulting in jets overlapping with missing transverse momentum. The implementation of semi-visible jets is done using the Pythia Hidden valley module to duplicate the QCD sector showering. In this work, several jet substructure observables have been examined to compare semi-visible jets (signal) and light quark/gluon jets (background). These comparisons were performed using different dark hadron fractions in the semi-visible jets. The extreme scenarios where signal consists either of entirely dark hadrons or visible hadrons offers a chance to understand the effect of the specific dark shower model employed in these comparisons. We attempt to decouple the behaviour of jet-substructure observables due to inherent semi-visible jet properties, from model dependence owing to the existence of only one dark shower model as mentioned above.

Identifying hadronic charmonium decays in hadron colliders

Identification of charmonium states at hadron colliders has mostly been limited to leptonic decays of the J/\psiJ/ψ. In this paper we present an algorithm to identify hadronic decays of charmonium states (J/\psiJ/ψ, \psiψ(2S), \chi_{c0,c1,c2}χc0,c1,c2) which make up the large majority of all decays. The algorithm is able to identify hadronic J/\psiJ/ψ decays with an efficiency of 36% while suppressing a background of quark and gluon jets by a factor 100.

Triggering On Hadronic Signatures In The Atlas Experiment-Developments For 2017 And 2018

Hadronic signatures are critical to the ATLAS physics program, and are used extensively for both the StandardModel measurements and searches for new physics. These signatures include generic quark and gluon jets, as well as jets originating from b-quarks or the decay of massive particles (such as electroweak bosons or top quarks). Additionally, missing transverse momentum from non-interacting particles provides an interesting probe in the search for new physics beyond the Standard Model. Developing trigger selections that target these events is a hugechallenge at the LHC due to the enormous rates associated with hadronic signatures. This challenge is exacerbated by the amount of pile-up activity, which continues to grow. In order to address these challenges, several new techniques were developed to significantly improve the potential of the 2017 dataset. An overview of how we triggeron hadronic signatures at the ATLAS experiment is presented, outlining the challenges of hadronic object triggering and describing the improvements performed over the course of the Run 2 LHC data-taking program. The performance in Run 2 data is shown, including demonstrations of the new techniques being used in 2017. We also discuss further critical developments implemented for the rest of Run 2 and their performance in early 2018 data.