1st year PG student talks

Speakers today:

The T2K Experiment and Identifying ve with Super-Kamiokande

by Josh Amey

T2K is an off-axis long baseline neutrino oscillation experiment, which uses a neutrino beam produced at J-PARC and detected at Super-Kamiokand. The formalism for neutrino oscillations is introduced, followed by an outline of T2K's current physics goals and experimental details. This is followed by a discussion of the potential for using Gadolinium in Super-Kamiokand for neutron tagging, enabling more efficient discrimination of neutrinos/anti-neutrinos.

CMS Trigger Upgrades

by Antoni Shtipliyski

The early stage physics programme of the CMS experiment culminated with the discovery of the Higgs Boson in 2012. However, in order to maintain its sensitivity to various physics channels and preserve efficient data-taking capabilities under the environments of increased luminosity and higher centre of mass energies it necessary to perform a series of upgrades to the detector hardware culminating with the development of a track-trigger system for operation at HL-LHC. This presentation outlines the different challenges imposed on the L1 trigger of CMS by operation at high pile-up environment and the proposed approaches in mitigating those while delivering high quality data for searches of physics beyond the Standard Model.

Prospects for H → τ τ Analyses in Run 2

by Daniel Winterbottom

H → τ τ is an important channel for probing the Higgs sector in both standard model (SM) and beyond the standard model (BSM) scenarios. Many BSM theories predict that, in addition to the recently discovered 125 GeV Higgs boson, there exists additional scalar bosons both charged and neutral. In the minimal supersymmetric standard model (MSSM) an additional 2 charged and 2 neutral (1 CP-even and 1 CP-odd) scalars are predicted to exist. The H → τ τ channel is used to limit the MSSM parameter space both by searching for the neutral scalars directly and through measurements of properties of the 125 GeV Higgs. For the SM Higgs anlayses, evidence of the H → τ τ decay has already been seen by CMS to a significance of 3.4σ in run 1 and a 5σ observation is expected in run 2. In addition to this, the large amount of Higgs data produced during run 2 will allow the individual Higgs production channels to be isolated. The vector boson fusion (VBF) channel is of particular interest in the SM H → τ τ analyses as it contains very low levels of background events in the signal region. This channel will be particularly strong at making measurements of the Higgs’s CP properties. Despite the advantages of this channel, no dedicated VBF H → τ τ L1 trigger is currently employed by CMS. Work designing such a trigger is ongoing and the progress of this work will be reviewed.

Higgs-to-Invisible Searches with the CMS experiment at the LHC

by Riccardo Di Maria

The Higgs boson discovery, along with the absence of any significant experimental evidence for physics beyond the standard model (SM), at the Large Hadron Collider (LHC) during Run-1 have placed constraints on new physics models. Although the observed 125 GeV boson is compatible with the SM Higgs boson, the existence of non-SM properties is not excluded due to the associated uncertainties. In addition, the possibility for further Higgs bosons with exotic decay modes remains. Invisible decay modes could be possible in interactions between the Higgs boson and dark matter (DM), where the former becomes the mediator between SM and DM particles. This type of model is referred to as a "Higgs-portal". Higgs to invisible (H(inv)) searches are performed by studying three main Higgs boson production modes: the ZH mode, in which the final state contains leptons or boson, the Vector Boson Fusion (VBF) production mode, where two hadronized quarks besides the H boson are present in the final state, and the gluon-gluon fusion mode (ggH). The different final states associated with these three modes mean that the results from the individual searches can be combined, leading to better sensitivity. Attempts to observe H(inv) are made using measurements of missing transverse energy (MET), due to the invisible decays of the Higgs boson, and comparisons with SM backgrounds. The CMS experiment at the LHC is the ideal place to perform such searches allowing full reconstruction of events and accurate measurement of the MET of an event.

Analysis of Higgs to two photons at CMS

by Ed Scott

The CMS experiment is one of two general-purpose detectors at the Large Hadron Collider (LHC) at CERN. In this talk I will discuss the CMS analysis of the Higgs decaying to two photons, including its importance in Run 1 of the LHC and its status and prospects for Run 2. I will also present my first work on the analysis, validating the hadronic jets present when the Higgs is produced in the Vector Boson Fusion mode.