from 28 June 2015 to 3 July 2015 (Africa/Johannesburg)
SAIP2015 Proceeding published on 17 July 2016
Exploring the Dark Sector extension to the Standard Model via the Higgs Portal
Presented by Prof. Simon CONNELL on 2 Jul 2015 from 11:10 to 11:30
Type: Oral Presentation
Track: Track B - Nuclear, Particle and Radiation Physics
The Standard Model (SM) is known to be incomplete. The introduction of a Dark Sector via an additional U(1)<sub>d</sub> gauge symmetry added to the SM Lagrangian provides a mechanism to introduce much needed new physics without perturbing the already excellent agreement between the SM theoretical description and the Electroweak Precision Observables (EWPO) experimental constraints. The model has a dark vector boson Z<sub>d</sub> which can mix with the hypercharge gauge boson with the coupling ε. This opens the Hypercharge Portal which can mediate the fluctuation of a Z to a Z<sub>d</sub>, or the decay of the Z<sub>d</sub> to SM leptons. If a dark Higgs singlet s also exists, this then breaks the U(1)<sub>d</sub>, opening the Higgs portal and also allowing for Higgs mass mixing between the SM and dark sectors, described by the Higgs mass mixing parameter, κ. Including dark fermionic fields in the Lagrangian allows for long-lived cold Dark Matter candidates. The various connections between the Dark and SM sectors allow descriptions of many key astro-physical phenomena. The Model is therefore a fascinating candidate for new physics beyond the SM. It becomes crucial to search for experimental signatures of this model. A promising avenue is to exploit the production of the dark force boson Z<sub>d</sub> via the Higgs Portal and the search for its decay back to SM leptons: H → h<sub>d</sub>→ Z<sub>d</sub>Z<sub>d</sub> → 4l. The detailed design and results of this search are presented.