Searches for Higgs Boson pair production with the ATLAS experiment at the LHC
June 6, 2022 - 4pm - Aula Conversi
Speaker: Alessandra Betti - Sapienza, Roma University
This seminar presents the searches for Higgs Boson pair production performed with the ATLAS experiment using 13 TeV pp collisions data from the LHC Run 2. The motivations for these searches are introduced and the rare Standard Model Higgs Boson pair production process at the LHC is described. Possible modifications of the characteristics of this process in beyond Standard Model scenarios are also described. The latest searches for Higgs Boson pairs performed by the ATLAS Collaboration with the full LHC Run 2 dataset in several decay channels are explained in details, describing event categorizations, background estimations and signal extraction methods, and their results are presented. Extrapolations of the recent results towards the High-Luminosity LHC are also discussed.
The POKER/NA64 experiment at CERN: current status and future perspectives
October 10, 2022 - 4pm - Aula Conversi
Speaker: Andrea Celentano - INFN Sezione di Genova
Light Dark Matter (LDM) is a new compelling hypothesis identifying Dark Matter with new sub-GeV “Dark Sector" states, neutral under Standard Model interactions and interfacing with our world through a new force. The NA64 experiment at CERN aims to produce Light Dark Matter particles through the interaction of a 100 GeV electron beam with an active thick target. The expected signal signature is the observation of events with a large missing energy, defined as the difference between the incoming particle energy and that measured in the target. An hermetic hadronic calorimeter and a high-efficiency veto detector are installed downstream the active target to reject background events, in which penetrating and/or long-lived Standard Model particles are produced. From the analysis of data collected so far, no evidence for LDM production has been found, allowing NA64 to set stringent exclusion limits on the LDM parameter space. Recently, the NA64 collaboration performed preliminary studies in order to run the experiment with a positron beam, as planned within the POKER (POsitron resonant annihilation into darK mattER) project, supported by a dedicated ERC grant. The new approach, based on LDM production through positron annihilation on atomic electrons, benefits from large signal yield and is characterized by a unique signal signature resulting from the underlying reaction dynamics: a peak in the missing energy distribution. The POKER goal is to perform a pilot run with an optimized active thick target to demonstrate the feasibility of the new technique, by exploring a so-far unknown territory in the Hidden Sector parameters space. In this talk, after a short introduction to the Light Dark Matter physics case, I will focus on the latest NA64 results, also reporting on the progresses in the positron beam run. I’ll then present the future prospects of the NA64 experiment, discussing the ongoing and future efforts involving different probes - muon and hadron beams - to explore the Dark Sector.