Ioanna Papavergou

Between the years 2015 and 2019, members of the Horizon 2020-funded Innovative Training Network named "AMVA4NewPhysics" studied the customization and application of advanced multivariate analysis methods and statistical learning tools to high-energy physics problems, as well as developed entirely new ones. Many of those methods were successfully used to improve the sensitivity of data analyses performed by the ATLAS and CMS experiments at the CERN Large Hadron Collider; several others, still in the testing phase, promise to further improve the precision of measurements of fundamental physics parameters and the reach of searches for new phenomena. In this paper, the most relevant new tools, among those studied and developed, are presented along with the evaluation of their performances.

The most recent CMS results from a search for supersymmetry (SUSY) with a compressed mass spectrum in leptonic final states will be presented. The search is targeting signatures with missing transverse momentum and two or three low-momentum (soft) leptons. The dataset used is collected by the CMS experiment during the Run-2 p-p collisions at $\sqrt{s} = {}$13 TeV at the LHC, and corresponds to an integrated luminosity of up to 137 fb$^{-1}$. The observed data are found to be in agreement with the standard model (SM) prediction and exclusion upper limits are set on the SUSY particles production cross section. The results are interpreted in terms of electroweakino and top squark pair production. In both cases, a small mass difference between the produced SUSY particles and the lightest neutralino is considered. A wino-bino and a higgsino simplified models are used for the electroweakino interpretation. Exclusion limits at 95% confidence level are set on $\tilde{\chi}_{2}^{0}$/$\tilde{\chi}_{1}^{\pm}$ masses up to 280 GeV for a mass difference between the $\tilde{\chi}_{2}^{0}$/$\tilde{\chi}_{1}^{\pm}$ and the lightest neutralino of 10 GeV for the wino-bino production. In the higgsino interpretation $\tilde{\chi}_{2}^{0}$/$\tilde{\chi}_{1}^{\pm}$ masses are excluded up to 210(150) GeV for a mass difference of 7.5(3) GeV. The results for the higgsino production are additionally interpreted in terms of a phenomenological minimal SUSY extension of the SM, excluding the higgsino mass parameter $\mu$ up to 180 GeV for bino mass parameter $M_1 = {}$800 GeV. Upper limits at 95% confidence level are set on the top squark pair production interpretation, excluding top squark masses up to 530 GeV in the four-body top squark decay model and up to 475 GeV in the chargino-mediated decay model for a mass difference between the top squark and the lightest neutralino of 30 GeV.

The CMS experiment implements a sophisticated two-level triggering system composed of Level-1, instrumented by custom-design hardware boards, and a software High Level Trigger.A new Level-1 trigger architecture with improved performance is now being used to maintain high physics efficiency for the more challenging luminosity conditions experienced during Run II.The CMS muon detector contains complementary and partially redundant muon detection systems: the Cathode Strip Chambers, Drift Tubes and Resistive Plate Chambers.The upgraded L1 muon trigger combines information from these three detectors to reconstruct muons and obtain a better efficiency and lower rates.Algorithms for the selection of events with muons, both for precision measurements and searches for new physics beyond the Standard Model, are described in detail.The performance of the upgraded muon trigger system will be presented, based on proton-proton collision data collected in 2017.

The Barrel Muon Track finder of the CMS experiment at the Large Hadron Collider uses custom processors to identify muons and measure their momenta in the central region of the CMS detector. An upgrade of the L1 tracking algorithm is presented, featuring a Kalman Filter in FPGAs, implemented using High Level Synthesis tools. The matrix operations are mapped to the DSP cores reducing resource utilization to a level that allows the new algorithm to fit in the same FPGA as the legacy one, thus enabling studies during nominal CMS data taking. The algorithm performance has been verified in CMS collisions during 2018 operations. The algorithm is also proposed for standalone muon tracking at the High Luminosity LHC. The algorithm development is complemented by ATCA processor R&D featuring a large ZYNQ Ultrascale+ SoC with high speed optical links.

The most recent CMS results from a search for supersymmetry (SUSY) with a compressed mass spectrum in leptonic final states will be presented. The search is targeting signatures with missing transverse momentum and two or three low-momentum (soft) leptons. The dataset used is collected by the CMS experiment during the Run-2 p-p collisions at $\sqrt{s} = {}$13 TeV at the LHC, and corresponds to an integrated luminosity of up to 137 fb$^{-1}$. The observed data are found to be in agreement with the standard model (SM) prediction and exclusion upper limits are set on the SUSY particles production cross section. The results are interpreted in terms of electroweakino and top squark pair production. In both cases, a small mass difference between the produced SUSY particles and the lightest neutralino is considered. A wino-bino and a higgsino simplified models are used for the electroweakino interpretation. Exclusion limits at 95% confidence level are set on $\tilde{\chi}_{2}^{0}$/$\tilde{\chi}_{1}^{\pm}$ masses up to 280 GeV for a mass difference between the $\tilde{\chi}_{2}^{0}$/$\tilde{\chi}_{1}^{\pm}$ and the lightest neutralino of 10 GeV for the wino-bino production. In the higgsino interpretation $\tilde{\chi}_{2}^{0}$/$\tilde{\chi}_{1}^{\pm}$ masses are excluded up to 210(150) GeV for a mass difference of 7.5(3) GeV. The results for the higgsino production are additionally interpreted in terms of a phenomenological minimal SUSY extension of the SM, excluding the higgsino mass parameter $\mu$ up to 180 GeV for bino mass parameter $M_1 = {}$800 GeV. Upper limits at 95% confidence level are set on the top squark pair production interpretation, excluding top squark masses up to 530 GeV in the four-body top squark decay model and up to 475 GeV in the chargino-mediated decay model for a mass difference between the top squark and the lightest neutralino of 30 GeV.