Polarized on Higgs? Measurement of the Higgs couplings to polarized vector bosons

The Standard Model (SM) is the theoretical framework at the basis of particle physics. It gives a description of the fundamental particles and their interactions. Elementary particles acquire their mass thanks to the spontaneous breaking of the electroweak symmetry and thanks to the introduction of a complex Higgs field. The Brout-Englert-Higgs mechanism adds to the theory a new particle, the Higgs boson, which has been discovered in 2012 by the ATLAS and CMS collaborations at the LHC. The study of its properties can either confirm its SM-like nature or may open doors to new physics. For example, there are Beyond Standard Model theories that foresee the existence of more than one Higgs boson. There are some features of this intriguing particle that have not been investigated yet. One of those, discussed in this thesis, is how it couples to longitudinally and transversally polarized vector bosons. The SM predicts the longitudinal coupling parameter and the transversal one to be equal and finely tuned in order to restore unitarity in the scattering of electroweak W bosons. If an anomalous coupling were observed, this would hint at new physics in the interactions between the Higgs and the vector bosons. In the present thesis, these couplings are studied in the case in which the Higgs is produced via vector boson fusion (VBF) and decays into the WW*→eνμν final state. The data analyzed has been collected by the ATLAS experiment at the LHC during 2015 and 2016, corresponding to an integrated luminosity of 36.1 fb^(-1). Anomalies in the longitudinal or transversal coupling directly affect the production cross-section, which presents a strong dependence on the longitudinal coupling and a mild one on the transversal one. The kinematic distributions of the two leading jets, related to the intrinsic structure of the VBF production vertex, carry information about the polarization. Exploiting these kinematic features, the first measurement on the longitudinal and transversal coupling parameters has been performed. Their values are found to be in agreement with the SM predictions within the errors

Measurement of cross sections and properties of the Higgs boson in decays to bosons using the ATLAS detector

Measurements of Higgs boson properties and cross sections measured in Higgs boson decays to two photons, two Z bosons, and two W bosons based on pp collision data collected at 13 TeV are presented. In addition, results from the combination of different decay channels are shown

Vector boson scattering : Recent experimental and theory developments

This document summarises the talks and discussions happened during the VBSCan Split17 workshop, the first general meeting of the VBSCan COST Action network. This collaboration is aiming at a consistent and coordinated study of vector-boson scattering from the phenomenological and experimental point of view, for the best exploitation of the data that will be delivered by existing and future particle colliders.Peer reviewe

VBSCan Thessaloniki 2018 Workshop Summary

International audienceThis document reports the first year of activity of the VBSCan COST Action network, as summarised by the talks and discussions happened during the VBSCan Thessaloniki 2018 workshop. The VBSCan COST action is aiming at a consistent and coordinated study of vector-boson scattering from the phenomenological and experimental point of view, for the best exploitation of the data that will be delivered by existing and future particle colliders

Testbeam evaluation of silicon strip modules for ATLAS Phase - II Strip Tracker Upgrade

The planned HL-LHC (High Luminosity LHC) is being designed to maximise the physics potential of the LHC with 10 years of operation at instantaneous luminosities of \mbox{$7.5\times10^{34}\;\mathrm{cm}^{-2}\mathrm{s}^{-1}$}. A consequence of this increased luminosity is the expected radiation damage requiring the tracking detectors to withstand hadron equivalences to over $1x10^{15}$ 1 MeV neutron equivalent per $cm^{2}$ in the ATLAS Strips system. The silicon strip tracker exploits the concept of modularity. Fast readout electronics, deploying 130nm CMOS front-end electronics are glued on top of a silicon sensor to make a module. The radiation hard n-in-p micro-strip sensors used have been developed by the ATLAS ITk Strip Sensor collaboration and produced by Hamamatsu Photonics. A series of tests were performed at the DESY-II test beam facility to investigate the detailed performance of a strip module with both 2.5cm and 5cm length strips before irradiation. The DURANTA telescope was used to obtain a pointing resolution of 2$\mu$m, with an additional pixel layer installed to improve timing resolution to $\sim$25ns. Results will show that prior to irradiation a wide range of thresholds (0.5-2.0 fC) meet the requirements of a noise occupancy less than $1x10^{-3}$ and a hit efficiency greater than 99\%

Asthma in patients admitted to emergency department for COVID-19: prevalence and risk of hospitalization

Non