Accuracy versus precision in boosted top tagging with the ATLAS detector

Abstract The identification of top quark decays where the top quark has a large momentum transverse to the beam axis, known as top tagging, is a crucial component in many measurements of Standard Model processes and searches for beyond the Standard Model physics at the Large Hadron Collider. Machine learning techniques have improved the performance of top tagging algorithms, but the size of the systematic uncertainties for all proposed algorithms has not been systematically studied. This paper presents the performance of several machine learning based top tagging algorithms on a dataset constructed from simulated proton-proton collision events measured with the ATLAS detector at √ s = 13 TeV. The systematic uncertainties associated with these algorithms are estimated through an approximate procedure that is not meant to be used in a physics analysis, but is appropriate for the level of precision required for this study. The most performant algorithms are found to have the largest uncertainties, motivating the development of methods to reduce these uncertainties without compromising performance. To enable such efforts in the wider scientific community, the datasets used in this paper are made publicly available.</jats:p

Whither the push and pull for integration : taking stock of Latin America’s declaratory regionalism

Repeated setbacks to a regional project in Latin America have given rise to a narrative portraying the region’s integration endeavor as a succession of failed attempts. Analysts concordantly highlight that Latin America’s institutional development and actual policy output do not live up to the integrationist discourse sustained in the region, and point to a series of obstacles standing in the way of deep integration. Such a perspective misses out, however, on an intriguing persistence of Latin American regionalism both in discourse as well as in repeated attempts to induce new impetus into the regional project. In an attempt to map out the basis for a more rigorous, theoretically guided approach to the subject, this paper brings the debates on the different push and pull factors of Latin America’s regionalist project together. Based on the premise that forces pushing towards integration are present within the region, it is argued that the dominant hypotheses in the study of regional integration do not address Latin America’s declaratory regionalism in a conclusive manner. The key to the broader picture of the region’s integration gap lies with a lack of determination to let the word follow the deed, and needs to apprehend of the political function declaratory regionalism has come to fulfill in the Latin American international system

Search for the Zγ decay mode of new high-mass resonances in pp collisions at s = 13 TeV with the ATLAS detector

This letter presents a search for narrow, high-mass resonances in the Zγ final state with the Z boson decaying into a pair of electrons or muons. The TeV pp collision data were recorded by the ATLAS detector at the CERN Large Hadron Collider and have an integrated luminosity of 140 fb−1. The data are found to be in agreement with the Standard Model background expectation. Upper limits are set on the resonance production cross section times the decay branching ratio into Zγ. For spin-0 resonances produced via gluon–gluon fusion, the observed limits at 95% confidence level vary between 65.5 fb and 0.6 fb, while for spin-2 resonances produced via gluon–gluon fusion (or quark–antiquark initial states) limits vary between 77.4 (76.1) fb and 0.6 (0.5) fb, for the mass range from 220 GeV to 3400 GeV

Pursuit of paired dijet resonances in the Run 2 dataset with ATLAS

New particles with large masses that decay into hadronically interacting particles are predicted by many models of physics beyond the Standard Model. A search for a massive resonance that decays into pairs of dijet resonances is performed using..