Search

Motivated by the excess in the diphoton production rate of the Higgs boson at the Large Hadron Collider (LHC), we investigate the possibility that one of the CP-even Higgs bosons of the extra U(1) extended minimal supersymmetric standard model can give a consistent result. We scan the parameter space for a standard-model-like Higgs boson such that the mass is in the range of 124-127 GeV and the production rate σB of the WW*, ZZ* modes is consistent with the standard model (SM) values, while that of γγ is enhanced relative to the SM value. We find that the SM-like Higgs boson is mostly the lightest CP-even Higgs boson and it has a strong mixing with the second lightest one, which is largely singletlike. The implications on Zγ production rate and properties of the other Higgs bosons are also studied. [ABSTRACT FROM AUTHOR]

We study the kinematic characteristics of the loop-induced effects on nonresonant Higgs pair production via gluon fusion in a type-II two Higgs doublet model with heavy vectorlike quarks. First, we performed a comprehensive analysis of the model phenomenology, suggesting an ansatz to satisfy theoretical and experimental constraints. Contrary to the usual expectation, the loop-induced effects can highly enhance the di-Higgs rate if the Higgs sector is extended into the wrong-sign limit (κt=-κb=1): the total cross section can be about three times as large as the SM expectation. As anomalous Higgs trilinear self-coupling of λhhh/λSMhhh=-0.5, 5.5 similarly enhances the di-Higgs rate, we made a comparative study focusing on the kinematic distributions. The threshold effects from the vectorlike quarks generate the correlated bumps in the distributions of the invariant mass of the Higgs boson pair and the transverse momentum of a Higgs boson, located at Mhh≃2MVLQ and phT≃MVLQ. Each bump has a long tail stretching toward the high region. The anomalous λhhh cases shift the distributions into low regions. In addition, we show the kinematic difference between the loop-induced effects and an s-channel wide resonance. Therefore, the kinematic regimes with high Mhh and high phT would have high potential to probe the loop-induced effects on the di-Higgs process, which is shown through full HL-LHC simulations in the b̅bb̅b and b̅bγγ final states. [ABSTRACT FROM AUTHOR]

The same-sign charged Higgs pair production via vector-boson scattering is a useful probe of the mass spectrum among the heavier scalar, pseudoscalar, and charged Higgs bosons in two-Higgs-doublet models. It has been shown that the production cross section scales as the square of the mass difference Δm=(mH0-mA0) in the alignment limit (cos(β-α)=0). We study the potential measurement of this same-sign charged Higgs boson pair production at the high-luminosity LHC and the proposed 27 TeV pp collider, with emphasis in the decay channel H±H±→(W±A0)(W±A0), which is in general the dominant mode when the charged Higgs mass is above the W±A0 threshold. We also examine the current allowed parameter space taking into account the theoretical constraints on the model, the electroweak precision test measurements, B decays, and direct searches in the H±→τ±ντ and H±→W±A0→(ℓ±νℓ)(μμ). [ABSTRACT FROM AUTHOR]

The model of heavy neutral leptons (HNLs) is one of the well-motivated models beyond the standard model from both theoretical and phenomenological point of views. It is an indispensable ingredient to explain the puzzle of tiny neutrino masses and the origin of the matter-antimatter asymmetry in our Universe, based on the models in which the simplest type-I seesaw mechanism can be embedded. The HNL with a mass up to the electroweak scale is an attractive scenario which can be readily tested in present or near-future experiments including the LHC. In this work, we study the decay rates of HNLs and find the sensitive parameter space of the mixing angles between the active neutrinos and HNLs. Since there are fewer collider studies of the mixing between ντ and HNL in literature compared with those of νe and νμ for the HNL of mass in the electroweak scale, we focus on the channel pp→W±(*)+X→τ±N+X to search for HNLs at the LHC 14 TeV. The targeted signature consists of three prompt charged leptons, which include at least two tau leptons. After the signal-background analysis, we further set sensitivity bounds on the mixing |UτN|2 with MN at high-luminosity LHC (HL-LHC). We predict the testable bounds from HL-LHC can be stronger than the previous LEP constraints and electroweak precision data (EWPD), especially for MN≲50  GeV can reach down to |UτN|²≈5×10-6. [ABSTRACT FROM AUTHOR]

We perform the most up-to-date comprehensive signal-background analysis for Higgs-pair production in HH→bb̅γγ channel at the HL-LHC and HL-100 TeV hadron collider, with the goal of probing the self-coupling λ3H of the Higgs boson which is normalized to its standard-model value of 1. We simulate all the standard-model signal and background processes and emphasize that the ggH(→γγ) background has been overlooked in previous studies. We find that, even for the most promising channel HH→bb̅γγ at the HL-LHC with a luminosity of 3000 fb-1, the significance is still not high enough to establish the Higgs self-coupling at the standard-model (SM) value. Instead, we can only constrain the self-coupling to -1.0<λ3H<7.6 at 95% confidence level after considering the uncertainties associated with the top-Yukawa coupling and the estimation of backgrounds. Here we also extend the study to the HL-100 TeV hadron collider. With a luminosity of 3 ab-1, we find there exists a bulk region of 2.6≲λ3H≲4.8 in which one cannot pin down the trilinear coupling. Otherwise, one can measure the coupling with a high precision. At the SM value, for example, we show that the coupling can be measured with about 20% accuracy. While assuming 30 ab-1, the bulk region reduces to 3.1≲λ3H≲4.3, and the trilinear coupling can be measured with about 7% accuracy at the SM value. [ABSTRACT FROM AUTHOR]

A muon jet (μ-jet) is a very special feature that consists of a cluster of collimated muons from the decay of a fast-moving light particle of mass about O(1 GeV). We will use this feature to search for very light particles from rare decays of the Higgs boson. For such a small angular separation of muons which might come from a long-lived particle, both ATLAS and CMS could have the displaced-vertexing-reconstruction capability. We use two simple models of the Higgs portal type to explore the possibilities of event topologies with two 2μ-jets, one 2μ-jet and one 4μ-jet, and two 4μ-jets in the final state at LHC-14. We also summarize existing constraints on these models. [ABSTRACT FROM AUTHOR]