Probing the Higgs sector of $$$$ Higgs triplet model at LHC

In this paper, we investigate the Higgs Triplet Model with hypercharge \(Y_{\varDelta }=0\) (HTM0), an extension of the Standard model, caracterized by a more involved scalar spectrum consisting of two CP even Higgs \(h^0, H^0\) and two charged Higgs bosons \(H^\pm \). We first show that the parameter space of HTM0, usually delimited by combined constraints originating from unitarity and BFB as well as experimental limits from LEP and LHC, is severely reduced when the modified Veltman conditions at one loop are also imposed. Then, we perform an rigorous analysis of Higgs decays either when \(h^0\) is the SM-like or when the heaviest neutral Higgs \(H^0\) is identified to the observed 125 GeV Higgs boson at LHC. In these scenarios, we perform an extensive parameter scan, in the lower part of the scalar mass spectrum, with a particular focus on the Higgs to Higgs decay modes \(H^0 \rightarrow h^0h^0, H^\pm \,H^\mp \) leading predominantly to invisible Higgs decays. Finally, we also study the scenario where \(h^0, H^0\) are mass degenerate. We thus find that consistency with LHC signal strengths favours a light charged Higgs with a mass about 176–178 GeV. Our analysis shows that the diphoton Higgs decay mode and \(H \rightarrow Z \gamma \) are not always positively correlated as claimed in a previous study. Anti-correlation is rather seen in the scenario where h is SM like, while correlation is sensitive to the sign of the potential parameter \(\lambda \) when H is identified to 125 GeV observed Higgs.     

Probing top-quark couplings indirectly at Higgs factories

We perform a global effective-field-theory analysis to assess the combined precision of Higgs couplings,triple gauge-boson couplings, and top-quark couplings, at future circular e~+e~- colliders, with a focus on runs below the tt production threshold. Deviations in the top-quark sector entering as one-loop corrections are consistently taken into account in the Higgs and diboson processes. We find that future lepton colliders running at center-of-mass energies below the tt production threshold can still provide useful information on top-quark couplings, by measuring virtual top-quark effects. With rate and differential measurements, the indirect individual sensitivity achievable is better than at the high-luminosity LHC. However, strong correlations between the extracted top-quark and Higgs couplings are also present and lead to much weaker global constraints on top-quark couplings. This implies that a direct probe of top-quark couplings above the tt production threshold is also helpful for the determination of Higgs and triple-gauge-boson couplings. In addition, we find that below the e~+e~-→tth production threshold, the top-quark Yukawa coupling can be determined by its loop corrections to all Higgs production and decay channels. Degeneracy with the ggh coupling can be resolved, and even a global limit is competitive with the prospects of a linear collider above the threshold. This provides an additional means of determining the top-quark Yukawa coupling indirectly at lepton colliders.     

Probing High-Scale and Split Supersymmetry with Higgs mass measurements

We study the range of Higgs masses predicted by High-Scale Supersymmetry and by Split Supersymmetry, using the matching condition for the Higgs quartic coupling determined by the minimal field content. In the case of Split Supersymmetry, we compute for the first time the complete next-to-leading order corrections, including two-loop renormalization group equations and one loop threshold effects. These corrections reduce the predicted Higgs mass by a few GeV. We investigate the impact of the recent LHC Higgs searches on the scale of supersymmetry breaking. In particular, we show that an upper bound of 127 GeV on the Higgs mass implies an upper bound on the scale of Split Supersymmetry of about ¹⁰⁸ GeV, while no firm conclusion can yet be drawn for High-Scale Supersymmetry.     

Probing compositeness with Higgs Boson decays at the LHC

We study how massive ghost-free gravity \(f(R)\) -modified theories, MGFTs, can be encoded into generic off-diagonal Einstein spaces. Using “auxiliary” connections completely defined by the metric fields and adapted to nonholonomic frames with associated nonlinear connection structure, we decouple and integrate in certain general forms the field equations in MGFT. Imposing additional nonholonomic constraints, we can generate Levi-Civita, LC, configurations and mimic MGFT effects via off-diagonal interactions of effective Einstein and/or Einstein–Cartan gravity with nonholonomically induced torsion. We show that imposing nonholonomic constraints it is possible reproduce very specific models of massive \(f(R)\) gravity studied in Cai et al. (arXiv:1307.7150, 2013), Klusoňet al. (Phys Lett B 726:918, 2013), Nojiri and Odintov (Phys Lett B 716:377, 2012) and Nojiri et al. (JCAP 1305:020, 2013). The cosmological evolution of ghost-free off-diagonal Einstein spaces is investigated. Certain compatibility of MGFT cosmology to small off-diagonal deformations of \(\Lambda \) CDM models is established.     

Photino pair creation in a magnetic field and astrophysical limits on slepton mass

The photino pair creation by a charged lepton in an external magnetic field is studied. New bounds on the slepton mass are obtained by analyzing the role of this process in the theory of stellar evolution. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 5 305–308 (10 March 1996)     

Probing the Higgs field using massive particles as sources and detectors

In the standard model, all massive elementary particles acquire their masses by coupling to a background Higgs field with a non-zero vacuum expectation value. What is often overlooked is that each massive particle is also a source of the Higgs field. A given particle can in principle shift the mass of a neighboring particle. The mass shift effect goes beyond the usual perturbative Feynman diagram calculations which implicitly assume that the mass of each particle is rigidly fixed. Local mass shifts offer a unique handle on Higgs physics since they do not require the production of on-shell Higgs bosons. We provide theoretical estimates showing that the mass shift effect can be large and measurable, especially near pair threshold, at both the Tevatron and the LHC. PACS 14.80.Bn; 13.40.Dk     

Probing two Higgs oscillations in a one-dimensional Fermi superfluid with Raman-type spin–orbit coupling

We theoretically investigate the Higgs oscillation in a one-dimensional Raman-type spin–orbit-coupled Fermi superfluid with the time-dependent Bogoliubov–de Gennes equations. By linearly ramping or abruptly changing the effective Zeeman field in both the Bardeen–Cooper–Schrieffer state and the topological superfluid state, we find the amplitude of the order parameter exhibits an oscillating behaviour over time with two different frequencies (i.e., two Higgs oscillations) in contrast to the single one in a conventional Fermi superfluid. The observed period of oscillations has a great agreement with the one calculated using the previous prediction [Volkov and Kogan, J. Exp. Theor. Phys. 38, 1018 (1974)], where the oscillating periods are now determined by the minimums of two quasi-particle spectrum in this system. We further verify the existence of two Higgs oscillations using a periodic ramp strategy with theoretically calculated driving frequency. Our predictions would be useful for further theoretical and experimental studies of these Higgs oscillations in spin–orbit-coupled systems.     

Limits on a light Higgs boson

We reexamine the bounds on a very light Higgs boson (φ) coming from limits on the decays K→π+φ and B→φ+X. We show that, if there are only three families, m_φ>2m_τ, and that regardless of the number of families M_φ>360 MeV.     

Limits on a composite Higgs boson

Precision electroweak data are generally believed to constrain the Higgs boson mass to lie below approximately 190 GeV at 95% confidence level. The standard Higgs model is, however, trivial and can only be an effective field theory valid below some high energy scale characteristic of the underlying nontrivial physics. Corrections to the custodial isospin violating parameter T arising from interactions at this higher energy scale dramatically enlarge the allowed range of Higgs mass. We perform a fit to precision electroweak data and determine the region in the (m(H),delta T) plane that is consistent with experimental results. Overlaying the estimated size of corrections to T arising from the underlying dynamics, we find that a Higgs mass up to 500 GeV is allowed.     

Speculations on a strongly interacting Higgs sector

Using the 1/N expansion, we argue that the O_2N Higgs-Goldstone model may be a good indicator of the behavior of the standard SU₂ ? U₁ electroweak model in the non-perturbative limit of a strongly interacting Higgs sector. We emphasize that there remains a physical scalar particle or resonance σ (Higgs remnant), whose mass (and width) will be set by the weak scale. However, its coupling to vector bosons is expected to be much stronger than the standard model Higgs of comparable mass. This provides evidence that there is an upper limit to the Higgs mass in the hundreds of GeV, regardless of whether naturalness constraints are imposed on the parameters of the effective lagrangian. We conclude with some comments about the possible relevance of this particle to the radiative events observed at the CERN $\text{p}\text{p}$ collider.