Right: Dependence of the signal reference cross section after all selections on the doubly charged Higgs boson massMH++. Right: Dependence of the signal reference cross section after all selections on the doubly charged Higgs boson mass MH++.
The Standard Model
The quantum numbers of SM fields corresponding to different gauge groups can be summarized as in Table 1.1. In addition to providing mass to the fermions, these terms also dictate the interaction of the Higgs boson h with the fermions.
Limitations of the Standard Model
SM theory cannot construct a renormalizable term for neutrino mass due to the absence of the right-handed neutrino of any flavor. A possible solution to acquire neutrino mass is to expand the particle content of the SM.
Few glimpses of BSM physics
In the sawtooth mechanism, the existence of the right-handed neutrino νR is assumed alongside the left-handed SM neutrino νL. One of the important issues in SM is the mass hierarchy with the fermion sector.
Main focus of the thesis
The explicit form of the Lagrangian containing the Dirac mass term for the charged sector of the model is given by The model potential can be written considering Φ1 as the SM Higgs doublet field.
Chapter outline
We summarize the studies carried out in the thesis and conclude with future prospects of the research. This chapter is devoted to the collider study of triplet fermions arising in the Type III seesaw model at high-energy e+e− collider.
Introduction
The larger value corresponds to the assumption of decay of the heavy neutral fermion exclusively toW `, and the heavily charged fermion toW ν. Single production of the charged and neutral heavy fermions in the electron-proton collider (LHeC) is studied in Ref. While there are studies of the indirect influence of the presence of triplet fermions in connection with Higgs pair production at the ILC [78], the direct production has not been explored to the best of our knowledge.
The advantages of the leptonic colliders, which are sensitive to the mixing of the heavy fermions with electrons at production level, as well as their clean environment, are exploited in the present study in which we explore the possible range of high-energy e+e− collisions in the search for heavy fermions, and discuss their sensitivity to mixing.
Present constraints on the model parameters
The individual decay widths and thus the total width have the usual strong dependence on the mass of the decaying Σ. Current constraints on the model parameters 29 dependence cancels out in the branching ratio (BR), leaving it virtually independent of mass for heavy fermions with mass above 500 GeV. Both of the above mixing scenarios give identical results in the case of LHC processes with ν in the final state, whereas the pair production processes are independent of the mixing.
e+e− colliders, on the other hand, have the advantage that the production mechanism itself can depend on the mixing of electron triplets, parameterized by Ve, directly via couplings of the form eΣV, where V =W, Z, in the case of both pair production and single production of heavy fermions.
Direct production of the triplets
In Table 2.4 the flowchart is presented together with the final meaning expected at an integrated luminosity of 100 fb−1. Note that the contribution of the t-channel to the cross-section here is proportional to the fourth power of the mixing parameter V`. In Table 2.7 the flowchart is presented together with the final meaning expected at an integrated luminosity of 300 fb−1.
The near-threshold amount of the pair production merVe= 0 is clearly different from the case withVe6= 0.
Dependence on the mixing
With the two selected channels of 2j +e+e− and 2b+e+e− originating from Σ±e∓ production and the final state 2b+E/ originating from Σ0ν could probe the model with MΣ closely of 1 TeV, assuming Ve = 0.05. The MΣ−Vetwo parameter limits obtainable from the final state 2j+e+E/ are indicated by the limit of this blue region. Similarly, the 3σ limits for MΣ−Ve obtained from the 4j+e+E/ final state are given by the boundary between the green and red regions, and that from 4j +e+e− and 4b+e+e− are given by the limits of respectively red and yellow areas and yellow and pink areas.
In the figure on the right, the two-parameter limits from 2b+E/ arising from Σ0ν are indicated by the border of the green and gray regions.
Conclusions
In pair production, the cross section for pair production Σ0 turns out to be negligibly small. On the other hand, the Σ+Σ− production process is present even in the absence of mixing, since the gauge coupling dictates the strength of the ZΣ+Σ− coupling, leading to the vapor production process through the channels. In the latter case, we consider Vµ 6= 0 to facilitate the decay of the triplet into SM leptons.
This may again be due to the fact that the cross sections are almost the same in both cases.
Introduction
In this chapter, we study the multileptonic channels for probing the heavy Higgs bosons in the context of the minimal left-right symmetric model at the 14 TeV LHC. We perform a detailed signal versus SM background analysis, which indicates that the channels we study have the potential to probe heavier mass doubly charged Higgs bosons with a High-Luminosity LHC. Flipping possibilities where the symmetries of the SM are extended also exist, as in left–right symmetric theories [22–33] , where minimal and non-minimal realizations naturally have Type I/II and Type III flipping mechanisms.
In their most minimalistic form, left-right symmetric theories are symmetric under parity transformations in the ultraviolet regime, although low-energy parity violation arises after spontaneous breaking of left-right symmetry at a high energy level.
The minimal left-right symmetric model
With the above assignments, the only parameters left to consider are the mass parameters of the heavy and light neutrino, MNi, with i. We consider the lightest degrees of freedom (i.e., left-handed neutrinos corresponding to i= 1, 2, 3) to have a mass of the order of 0.1 eV to agree with the cosmological data . Having fixed all the physical masses of the neutrino and assuming that|f vL|<<.
This affects the decay pattern of the scalar fields, which will rarely decay to non-leptonic final states.
LHC phenomenology
These last components of the background can potentially be rejected by (at least loosely) vetoing the presence of missing energy and b-labeled jets in the final state. In the right panel of Figure 3.3, we generalize our conclusions to heavier scenarios and present the dependence of the confidence cross section associated with the production of the four-lepton signal on the mass of the doubly charged Higgs boson. We then reconstruct the invariant mass of the same-sign dilepton system and use it as an extra handle on the signal, required.
These choices are sufficient to obtain a good sensitivity to the signal, as shown in the left panel of Figure 3.4 in which we present the significance dependence of s calculated as in Eq.
Conclusions
Unlike the four-leptonic channel, all the luminosity expected to be collected during the high-luminosity operation of the LHC will only allow us to barely reach the massive TeV regime. For our study, we consider a scenario with doubly charged scalar masses fixed at 800 GeV, heavy right neutrinos with masses of 12 TeV and a WR boson of 10 TeV. Although the cross sections associated with the production of these doubly charged and singly charged light states have been found to be around 0.1–1 fb, we have shown, based on state-of-the-art Monte Carlo simulations, that a strategy simple selection may allow observation of the resulting quadrupleptonic and trileptonic signals within the reach of the LHC's high-luminosity stage.
In other words, MLRSM singly charged and doubly charged Higgs bosons lying in the TeV range could be achieved in the not-too-distant future thanks to an analysis strategy that yields a virtually background-free environment.
Introduction
The destruction is typically mediated by the SM Higgs boson in the s-channel or by the gauge bosons in the t-channel. In this study we consider the possible presence of heavily charged fermions (χ±) that exist in combination with the scalar DM. Being Z2 foreign, such fermions enable Yukawa couplings to the dark scalar field along with standard fermions.
One can note that these studies have two differences with the case proposed in this study.
Model description
We continue with a brief description of the model in Section 4.2 followed by the introduction to the simulation tools with ILC detector concept and the signal and SM background processes in Section 4.3. The inert doublet in the form of the physically charged and neutral fields can be written as Φ2. With this, the physical spectrum of the model has two charged scalars H±, one is neutral scalar, H0 and the other is neutral pseudo-scalar A0 coming from the Φ2 file.
The output is controlled by the coupling of the gauge and the mass of the particle with a cross section lying on the order of pb.
Signal background processes, event generation, detec- tor simulation
The cross section with electron beam of polarization degree Pe and positron beam of polarization Pp can be written in the form of the cross section with beam of 100% polarizations as. 4.6) The cross sections for a selected mχfor different center of mass energies of√. 4-fermion leptonic (e+e− → Ze+e− → `+`−ν`ν¯`): Final states of 4 leptons consisting mainly of processes through Z and electron, positron production. 4-fermion semileptonic (e+e− → Zν`ν¯` → 2jν`ν¯`): Final state of 4 fermions consisting primarily of processes through Zand neutrino and anti-neutrino production.
Those events containing a neutrino-anti-neutrino pair and two jets are the background of our signal.
Analysis and discussion
We explain the methods and performance of the signal selection and background rejection in section 4.4. The invariant mass of the two jets (Mjet1jet2) does not go beyond about 100 GeV. Note that the events with a small number of events are not visible in the plot.
The decay pattern of BP2 is the same as that of BP1, with the only difference being the reduced mχ, and a consequent increase in cross-sectional area.
Conclusions
Look for evidence of the Type-III seesaw mechanism in Multilepton final states in proton-proton collisions at √. Heavily charged leptons from type III seesaw and pair production of the Higgs boson H at the International Linear e+ e-Collider. Production of the charged Higgs bosons at the CERN Large Hadron Collider in the left-right symmetric model.
Exploring the doubly charged Higgs boson of the left-right symmetric model using vector boson fusion-like events at the LHC. Probing the Higgs sector of the minimal left-right symmetric model at Future Hadron Colliders. Anatomy of the Inert Two Higgs Doublet Model in the Light of LHC and Non-LHC Dark Matter Searches.
