Exploring the Higgs portal

Journal of High Energy Physics, 2012

We consider the impact of new exotic colored and/or charged matter interacting through the Higgs portal on Standard Model Higgs boson searches at the LHC. Such Higgs portal couplings can induce shifts in the effective Higgs-gluon-gluon and Higgsphoton-photon couplings, thus modifying the Higgs production and decay patterns. We consider two possible interpretations of the current LHC Higgs searches based on ∼ 5 fb −1 of data at each detector: 1) a Higgs boson in the mass range (124 − 126) GeV and 2) a hidden heavy Higgs boson which is underproduced due to the suppression of its gluon fusion production cross section. We first perform a model independent analysis of the allowed sizes of such shifts in light of current LHC data. As a class of possible candidates for new physics which gives rise to such shifts, we investigate the effects of new scalar multiplets charged under the Standard Model gauge symmetries. We determine the scalar parameter space that is allowed by current LHC Higgs searches, and compare with complementary LHC searches that are sensitive to the direct production of colored scalar states.

2019

With Run 2 of the LHC currently under way at a record-breaking centre of mass energy of 13 TeV, new physics searches are becoming more feasible than ever before. In particular, the ATLAS and CMS collaborations are beginning to focus more on searches which may extend the Higgs sector of the Standard Model. Here it is shown that Run 1 data from both ATLAS and CMS hint at the existence of a new heavy scalar with a mass around 270 GeV. This work will also extend this idea by introducing a full Two-Higgs Doublet Model and outlining the potential Run 2 searches which could constrain the parameters of such a model, should it exist in nature. This will be presented in the context of searches for Higgs production in association with missing energy, leptons and large jet multiplicities. Some preliminary studies related to the rates and kinematic distributions of processes of interest are presented and their implications are discussed in the context of the ATLAS Z+MET search.

2014

The Standard Model (SM) has well known deficiencies, and there is clearly need for new physics beyond the SM. The particles manifesting the new physics would interact at most weakly with the SM particles, and hence they are termed dark. The Higgs boson is potentially a favourable route for the production of the dark particles. There are a large class of theories where couplings or mixings at the Higgs level leads to exotic Higgs decays, which nonetheless do not significantly disturb the known physics below the Higgs level. This is therefore a significant potential discovery opportunity. We present studies which have been carried out as part of designing the search for the exotic decay of the SM Higgs which proceeds via a dark force back to SM four leptons, H → ZdZd → 4l.

Journal of High Energy Physics

We study the observability of the Higgs boson in the "charming Higgs" model. In this model the Higgs boson primarily undergoes a cascade decay to four charm quarks via light intermediate pseudoscalars. Such a decay allows the Higgs boson to escape the most stringent LEP bounds on the Standard Model Higgs boson mass. If the light pseudoscalars are sufficiently light they become highly boosted and their decay products collimated into jets. We show that by using jet substructure techniques, this model is potentially observable at the LHC. For a Higgs boson mass of 100 GeV and light pseudoscalar mass of 12 GeV, we find a signal significance of 3.8 sigma with a luminosity of 30 fb^-1 and that a 5 sigma significance can be obtained with 50 fb^-1 of luminosity at the 14 TeV LHC.

The Standard Model (SM) has well known deficiencies, and there is clearly need for new physics beyond the SM. The particles manifesting the new physics would interact at most weakly with the SM particles, and hence they are termed dark. The Higgs boson is potentially a favourable route for the production of the dark particles. There are a large class of theories where couplings or mixings at the Higgs level leads to exotic Higgs decays, which nonetheless do not significantly disturb the known physics below the Higgs level. This is therefore a significant potential discovery opportunity. We present the motivation and progress made in the studies which have been carried out as part of designing the search for the exotic decay of the SM Higgs which proceeds via a dark force back to SM four leptons, H → Z d Z d → 4l from the LHC run 1 data using the ATLAS detector.

Physical Review D, 2010

The Large Electron-Positron (LEP) collider experiments have constrained the mass of the Standard Model (SM) Higgs boson to be above 114.4 GeV . This bound applies to all extensions of the SM where the coupling of a Higgs boson to the Z boson and also the Higgs decay profile do not differ much from the SM one. However, in scenarios with extended Higgs sectors, this coupling can be made very small by a suitable choice of the parameters of the model. In such cases, the lightest CP-even Higgs boson mass can in turn be made very small. Such a very light Higgs state, with a mass of the order of the Z boson one or even smaller, could have escaped detection at LEP. In this work we perform a detailed parton level study on the feasibility of the detection of such a very light Higgs particle at the Large Hadron Collider (LHC) in the production process pp → hj → τ + τ − j, where j is a resolved jet. We conclude that there are several models where such a Higgs state could be detected at the LHC with early data.

2021

The ATLAS and CMS experiments have an ambitious search program for charged Higgs bosons. The two main searches for H± at the LHC have traditionally been performed in the τν and tb decay channels, as they provide the opportunity to probe complementary regions of the Minimal SuperSymmetric Model (MSSM) parameter space. Charged Higgs bosons may decay also to light quarks, H± → cs/cb, which represent an additional probe for the mass range below mt. In this work, we focus on H± → μν as an alternative channel in the context of two Higgs doublet model type III. We explored the prospect of looking pp→ tbH±, followed by H± → μν signal at the LHC. Such a scenario appears in 2HDM type-III where couplings of the charged Higgs are enhanced to μν. Almost all the experimental searches rely on the production and decay of the charged Higgs are taken into account. We show that for a such scenario, the above signal is dominant for most of the parameter space, and H± → μν can be an excellent complement...

2014

This report summarizes the work of the Energy Frontier Higgs Boson working group of the 2013 Community Summer Study (Snowmass). We identify the key elements of a precision Higgs physics program and document the physics potential of future experimental facilities as elucidated during the Snowmass study. We study Higgs couplings to gauge boson and fermion pairs, double Higgs production for the Higgs self-coupling, its quantum numbers and CP-mixing in Higgs couplings, the Higgs mass and total width, and prospects for direct searches for additional Higgs bosons in extensions of the Standard Model. Our report includes projections of measurement capabilities from detailed studies of the Compact Linear Collider (CLIC), a Gamma-Gamma Collider, the International Linear Collider (ILC), the Large Hadron Collider High-Luminosity Upgrade (HL-LHC), Very Large Hadron Colliders up to 100 TeV (VLHC), a Muon Collider, and a Triple-Large Electron Positron Collider (TLEP).

2005

This working group has investigated Higgs boson searches at the Tevatron and the LHC. Once Higgs bosons are found their properties have to be determined. The prospects of Higgs coupling measurements at the LHC and a high-energy linear e+e-collider are discussed in detail within the Standard Model and its minimal supersymmetric extension (MSSM). Recent improvements in the theoretical knowledge of the signal and background processes are presented and taken into account. The residual uncertainties are analyzed in detail. Theoretical progress is discussed in particular for the gluon-fusion processes gg-+ H(+j), Higgsbremsstrahlung off bottom quarks and the weak vector-boson-fusion (VBF) processes. Following the list of open questions of the last Les Houches workshop in 2001 several background processes have been. calculated at next-to-leading order, resulting in a significant reduction of the theoretical uncertainties. Further improvements have been achieved for the Higgs sectors of the MSSM and NMSSM. This report summarizes our work performed before and after the workshop in Les Houches. Part A describes the theoretical developments for signal and background processes. Part B presents recent progress in Higgs boson searches at the Tevatron collider. Part C addresses the determination of Higgs boson couplings, part D the measurement of tan ,O and part E Higgs boson searches in the VBF processes at the LHC. Part F summarizes Higgs searches in supersymmetric Higgs decays, part G photonic Higgs decays in Higgs-strahlung processes at the LHC, while part H concentrates on MSSM Higgs bosons in the intense-coupling regime at the LHC. Part I presents progress in charged Higgs studies and part J the Higgs discovery potential in the NMSSM at the LHC. The last part K describes Higgs coupling measurements at a 1 TeV linear e+e-collider.

Physical Review Letters, 2010