Professor Amanda Cooper-Sarkar

Abstract:

A bstract A search for charged Higgs bosons decaying into a top quark and a bottom quark is presented. The data analysed correspond to 139 fb − 1 of proton-proton collisions at $$ \sqrt{s} $$ s = 13 TeV, recorded with the ATLAS detector at the LHC. The production of a heavy charged Higgs boson in association with a top quark and a bottom quark, pp → tbH + → tbtb , is explored in the H + mass range from 200 to 2000 GeV using final states with jets and one electron or muon. Events are categorised according to the multiplicity of jets and b -tagged jets, and multivariate analysis techniques are used to discriminate between signal and background events. No significant excess above the background-only hypothesis is observed and exclusion limits are derived for the production cross-section times branching ratio of a charged Higgs boson as a function of its mass; they range from 3.6 pb at 200 GeV to 0.036 pb at 2000 GeV at 95% confidence level. The results are interpreted in the hMSSM and $$ {M}_h^{125} $$ M h 125 scenarios.

Abstract:

Experimental tests of the Standard Model of particle physics (SM) find excellent agreement with its predictions. Since the original formation of the SM, experiments have provided little guidance regarding the explanations of phenomena outside the SM, such as the baryon asymmetry and dark matter. Nor have we understood the aesthetic and theoretical problems of the SM, despite years of searching for physics beyond the Standard Model (BSM) at particle colliders. Some BSM particles can be produced at colliders yet evade being discovered, if the reconstruction and analysis procedures not matched to characteristics of the particle. An example is particles with large lifetimes. As interest in searches for such long-lived particles (LLPs) grows rapidly, a review of the topic is presented in this article. The broad range of theoretical motivations for LLPs and the experimental strategies and methods employed to search for them are described. Results from decades of LLP searches are reviewed, as are opportunities for the next generation of searches at both existing and future experiments.Comment: 79 pages, 36 figures, submitted to Progress in Particle and Nuclear Physic

Abstract:

Abstract The paper presents a measurement of the Standard Model Higgs Boson decaying to b -quark pairs in the vector boson fusion (VBF) production mode. A sample corresponding to 126 $$\hbox {fb}^{-1}$$ fb - 1 of $$\sqrt{s} = 13\,\text {TeV}$$ s = 13 TeV proton–proton collision data, collected with the ATLAS experiment at the Large Hadron Collider, is analyzed utilizing an adversarial neural network for event classification. The signal strength, defined as the ratio of the measured signal yield to that predicted by the Standard Model for VBF Higgs production, is measured to be $$0.95^{+0.38}_{-0.36}$$ 0 . 95 - 0.36 + 0.38 , corresponding to an observed (expected) significance of 2.6 (2.8) standard deviations from the background only hypothesis. The results are additionally combined with an analysis of Higgs bosons decaying to b -quarks, produced via VBF in association with a photon.