Expected b-tagging performance with the ATLAS Phase 2 detector and MVA developments for ttHbb analysis with Particle-Flow jets

• Neelam Kumari (Centre de Physique des Particules de Marseille CPPM)

With the ATLAS detector operating under High-Luminosity LHC conditions, the ATLAS detector will be upgraded to maintain high performance at peak instantaneous luminosity of 7.5 x 1034 cm-2s-1, corresponding to an average pile-up of about 200 interactions per bunch crossing. The new Inner Tracker (ITk), with extended pseudorapidity coverage up to |eta| < 4, is planned to run for more than 10 years, during which the LHC aims to produce 4 ab-1 of integrated luminosity. The algorithms used to identify hadronic jets from b-quarks rely heavily on track reconstruction and therefore on the design of the detector. The ITk aims to provide significant discriminating power between b- hadron and light-flavour jets, even in the forward region which has not been accessible with the current tracker. Maintaining high b-tagging performance under harsh HL-LHC pile-up conditions will also be one of the key elements in view of a potential observation of di-Higgs production. The expected b-tagging performance with the new ITk detector and the associated software developments will be presented in the talk. Next part of the talk will focus on the ttH (H→bb) analsyis with one or more leptons in the final states with the ATLAS detector using the data collected during the LHC Run 2. With many final-state particles in this channel the main challenges were the low efficiency to reconstruct and model the large irreducible background. Thus, the contribution targets to the next round of ttHbb analysis exploiting the recent jet analysis Particle Flow technique. Efforts on retraining the MultiVariate Analysis discriminants using PFlow jets will be discussed. The talk will also focus on implemention of the Deep neural networks (DNNs) targeting to perform the Higgs kinematic regression and multi-background classification facilitating the definition of ttb/B/bb/c control regions with a single tool.

Analysis of the first KM3NeT-ORCA data

• zineb aly (CPPM - AMU)

ORCA, Oscillation Research with Cosmics in the Abyss, is the low energy KM3NeT neutrino underwater detector, located in the French Mediterranean sea. It comprises a dense array of optical modules designed to detect the emitted Cherenkov light emitted from charged particles resulting from neutrino interactions in the vicinity of the detector. Its main physics goal is the determination of the neutrino mass hierarchy by quantifying the matter-induced effect on the oscillation probabilities of atmospheric neutrinos in the energy range, 3-50 GeV, where the effects of neutrino oscillation phenomena are dominant. In 2019, four detection units were operational. Two more had been added in early 2020. This work presents an overview of the detector performance in 2019 and 2020 as well as its sensitivity to neutrino oscillations. PS: four extra detections units have been deployed in Late November 2021! For a total of 10 DUs. ORCA is growing!