Pair production of Two Higgs Doublet Model light Higgs bosons in γγ collisions

We study the production of a pair of light, neutral, CP-even Higgs bosons in photon–photon collisions within the general Two Higgs Doublet Model (THDM). This is a process for which the lowest order contribution in both, the Standard Model and the THDM, appears at one loop. We find that the cross section for this process can be much larger in the THDM than in the Standard Model and the number of events expected at the Photon Collider will allow a determination of some of the parameters in the scalar potential.     

Higgs radiation off top quarks in high-energye + e − colliders

Higgs particles can be radiated off heavy top quarks which will be produced copiously in high energye ⁺ e ^? colliders. This process can be used to measure the Higgs-top quark coupling. We present the cross section for the production of Higgs bosons in the Standard Model. In addition we have studied the production of neutral and charged Higgs particles in association with heavy fermions in the Minimal Supersymmetric Standard Model.     

Towards Higgs boson production in gluon fusion to NNLO in the MSSM

We consider the Higgs boson production in the gluon-fusion channel to next-to-next-to-leading order within the Minimal Supersymmetric Standard Model. In particular, we present analytical results for the matching coefficient of the effective theory and study its influence on the total production cross section in the limit where the masses of all MSSM particles coincide. For supersymmetric masses below 500 GeV it is possible to find parameters leading to a significant enhancement of the Standard Model cross section, the K-factors, however, change only marginally.     

Enhancement of “CP-odd” Higgs boson production in the minimal supersymmetric Standard Model with explicit CP-violation

We calculate the production cross section of the “CP-odd” Higgs boson via gluon fusion in the minimal supersymmetric Standard Model with explicit CP-violation in the stop sector. We show that there is a parameter region in which the cross section is enhanced by a factor of about 1000, as compared to the case without CP-violation in the stop sector. In the parameter region where the “CP-odd” Higgs boson can decay into a stop pair, the stop pair events will be the important signature of the enhanced “CP-odd” Higgs boson production. In the case where the “CP-odd” Higgs boson cannot decay into any superparticles, the γγ and ττ decay channels could become important for discovering the “CP-odd” Higgs boson. We also discuss the constraints from electric dipole moments of electron, neutron and mercury on the viable parameter space mentioned above.     

Higgs production via gluon fusion in a six-dimensional universal extra dimension model on S 2/Z 2

We investigate Higgs boson production process via gluon fusion at LHC in our six-dimensional universal extra dimension model compactified on a spherical orbifold S ²/Z ₂. We find a striking result that the Higgs production cross section in our model is predicted to have 30(10)% enhancement compared to the predictions of the Standard Model (the minimal universal extra dimension model) for the compactification scale of order 1 TeV.     

NLO electroweak corrections to Higgs boson production at hadron colliders

Results for the complete NLO electroweak corrections to Standard Model Higgs production via gluon fusion are included in the total cross section for hadronic collisions. Artificially large threshold effects are avoided working in the complex-mass scheme. The numerical impact at LHC (Tevatron) energies is explored for Higgs mass values up to 500 GeV (200 GeV). Assuming a complete factorization of the electroweak corrections, one finds a +5% shift with respect to the NNLO QCD cross section for a Higgs mass of 120 GeV both at the LHC and the Tevatron. Adopting two different factorization schemes for the electroweak effects, an estimate of the corresponding total theoretical uncertainty is computed.     

Charged Higgs Pair Production in a General Two Higgs Doublet Model at e^＋e^- and μ^＋μ^- Linear Colliders

In this paper, charged Higgs pair production through l^＋l^- → H^＋ H^-, where l = e or μ, is studied within the framework of a general Two Higgs Doublet Model （2HDM）. The analysis is relevant to a future e^＋e^- or μ^＋ μ^- collider operating at center of mass energy of √s = 500 GeV. Two different scenarios of small and large a values are studied. Here a is the parameter, which diagonMizes the neutral CP-even Higgs boson mass matrix. Within the Minimal Supersymmetric Standard Model （MSSM）, cross section of this process is almost the same at e＋ e- and #＋#- colliders. It is shown that at e^＋e^- eolliders within a general 2HDM, cross section is not sensitive to the mass of neutral Higgs bosons, however, it can acquire large values up to several picobarn at μ^＋μ^- colliders with the presence of heavy neutral Higgs bosons. A scan over Higgs boson mass parameter space is performed to analyze the effect of large masses of neutral Higgs bosons involved in the s-channel propagator and thus in the total cross section of this process.     

Production of neutral Higgs-boson pairs at LHC

The reconstruction of the Higgs potential in the Standard Model or supersymmetric theories demands the measurement of the trilinear Higgs couplings. These couplings affect the multiple production of Higgs bosons at high energy colliders. We present a systematic overview of the cross sections for the production of pairs of (light) neutral Higgs bosons at the LHC. The analysis is carried out for the Standard Model and its minimal supersymmetric extension. Received: 30 March 1999 / Published online: 28 May 1999     

LHC: Standard Higgs and hidden Higgs

Interpretations of Higgs searches critically involve production cross sections and decay probabilities for different analysis channels. Mixing effects can reduce production rates, while invisible decays can reduce decay probabilities. Both effects may transparently be quantified in Higgs systems where a visible Higgs boson is mixed with a hidden sector Higgs boson. Recent experimental exclusion bounds can be re-interpreted in this context as a sign for non-standard Higgs properties. Should a light Higgs boson be discovered, then our analysis will quantify how closely it may coincide with the Standard Model.     

Higgs boson production and decay in little Higgs models with T-parity

We study Higgs boson production and decay in a certain class of little Higgs models with T-parity in which some T-parity partners of the Standard Model (SM) fermions gain their masses through Yukawa-type couplings. We find that the Higgs boson production cross section of a 120 GeV Higgs boson at the CERN LHC via gg fusion process at one-loop level could be reduced by about 45%, 35% and 20%, as compared to its SM prediction, for a relatively low new particle mass scale f=600, 700 and 1000 GeV, respectively. On the other hand, the weak boson fusion cross section is close to the SM value. Furthermore, the Higgs boson decay branching ratio into di-photon mode can be enhanced by about 35% in small Higgs mass region in certain case, for the total decay width of Higgs boson in the little Higgs model is always smaller than that in the SM.     

Production and two-photon decay of the MSSM scalar Higgs bosons at the LHC

We consider the production and two-photon decay of theCP-even Higgs bosons (h ⁰ andH ⁰) of the Minimal Supersymmetric Standard Model (MSSM) at the Large Hadron Collider. We study in detail the dependence of the cross section on various parameters of the MSSM, especially the dependence on the mixing effects in the squark sector due to the Higgs bilinear parameterμ and the soft supersymmetry breaking parameterA. We find that the cross section for the production of these Higgs bosons has a significant dependence on the parameters which determine the chiral mixing in the squark sector. The cross section times the two-photon branching ratio ofh ⁰ is of the order of 15–25 fb in much of the parameter space that remains after imposing the present experimental constraints. For theH ⁰ the two-photon branching ratio is only significant if theH ⁰ is light, but then the cross section times the branching ratio may exceed 200 fb. The QCD corrections due to quark loop contributions are known to increase the cross section by 50%. We find the dependence of the cross section on the gluon distribution function used to be rather insignificant.     

Correlation Between the Scaling Factor of the Yukawa Coupling and Cross Section for the e + e − → h h f f ¯ $e^{+} e^{-} \rightarrow hhf\overline {f}$ (f≠t) in Type-I 2HDM

International Journal of Theoretical Physics - The objective of this study is to correlate the scaling factor of the Standard Model (SM) like Higgs boson and the cross section ratio of the process...     

Hidden sector effects on double Higgs production near threshold at the LHC

In this Letter we study a novel effect of a hidden sector coupling to the standard model Higgs boson: an enhancement of the Higgs pair production cross section near threshold due to bound state effects. After summing the ladder contributions of the hidden sector to the effective ggHH coupling, we find the amplitude for gluon-gluon scattering via a Higgs loop. We relate this amplitude to the double Higgs production cross section via the optical theorem. We find that enhancements of the O(100) for the partonic cross section near the threshold region can be obtained for a hidden sector strongly coupled to the Higgs boson. The corresponding cross section at the LHC can be as large as O(10) times the SM result for extreme values of the coupling. The detection of such an effect could in principle lead to important information about the hidden sector.     

Higgs physics: Theory

The theoretical aspects of the physics of Higgs bosons are reviewed focussing on the elements that are relevant for the production and detection at present hadron colliders. After briefly summarizing the basics of electroweak symmetry breaking in the Standard Model, the Higgs production at the LHC and at the Tevatron is discussed, with some focus on the main production mechanism, the gluon?Cgluon fusion process, and the main Higgs decay modes and the experimental detection channels are discussed. Then the case of the minimal supersymmetric extension of the Standard Model is briefly surveyed. In the last section, the prospects for determining the fundamental properties of the Higgs particles are reviewed, once they have been experimentally observed.     

SUSY background to neutral MSSM Higgs boson searches

Within the Minimal Supersymmetric Standard Model (MSSM) the production and decay of superpartners can give rise to backgrounds for Higgs boson searches. Here MSSM background processes to the vector boson fusion channel with the Higgs boson decaying into two tau leptons or two W-bosons are investigated, giving rise to dilepton plus missing transverse momentum signals of the Higgs boson. Starting from a scenario with relatively small masses of the supersymmetric (SUSY) particles, with concomitant large cross section of the background processes, one obtains a first conservative estimate of the background. Light chargino pair production plus two jets, lightest and next-to-lightest neutralino production plus two jets as well as slepton pair production plus two jets are identified as important contributions to the irreducible SUSY background. Light chargino and next-to-lightest neutralino production plus two jets and next-to-lightest neutralino pair production plus two jets give rise to reducible backgrounds, which can be larger than the irreducible ones in some scenarios. The relevant distributions are shown and additional cuts for MSSM background reduction are discussed. Extrapolation to larger squark masses is performed and shows that MSSM backgrounds are quite small for squark masses at the current exclusion limits.     

Soft gluon radiation in Higgs boson production at the LHC

We examine the contributions of soft gluons to the Higgs production cross section at the LHC in the Standard Model and its minimal supersymmetric extension. The soft gluon radiation effects of this reaction share many features with the Drell-Yan process, but arise at lowest order from a purely gluonic initial state. We provide an extension of the conventional soft gluon resummation formalism to include a new class of contributions which we argue to be universal, and resum these and the usual Sudakov effects to all orders. The effect of these new terms is striking: only if they are included, does the expansion of the resummed cross section to next-to-leading order reproduce the exact result to within a few percent for the full range of Higgs boson masses. We use our resummed cross section to derive next-to-next-to-leading order results, and their scale dependence. Moreover, we demonstrate the importance of including the novel contributions in the resummed Drell-Yan process.     

Top-quark mediated effects in hadronic Higgs-Strahlung

Novel contributions to the total inclusive cross section for Higgs-Strahlung in the Standard Model at hadron colliders are evaluated. Although formally of order a_s²\alpha_{s}^{2}, they have not been taken into account in previous NNLO predictions. The terms under consideration are induced by Higgs radiation off top-quark loops and thus proportional to the top-quark Yukawa coupling. At the Tevatron, their effects to WH production are below 1% in the relevant Higgs mass range, while for ZH production, we find corrections between about 1% and 2%. At the LHC, the contribution of the newly evaluated terms to the cross section is typically of the order of 1%–3%. Based on these results, we provide updated predictions for the total inclusive Higgs-Strahlung cross section at the Tevatron and the LHC.     

Testing Higgs self-couplings at e^+e^- linear colliders

To establish the Higgs mechanism sui generis experimentally, the self-energy potential of the Higgs field must be reconstructed. This task requires the measurement of the trilinear and quadrilinear self-couplings, as predicted, for instance, in the Standard Model or in supersymmetric theories. The couplings can be probed in multiple Higgs production at high-luminosity linear colliders. Complementing earlier studies to develop a coherent picture of the trilinear couplings, we have analyzed the production of pairs of neutral Higgs bosons in all relevant channels of double Higgs-strahlung, associated multiple Higgs production and WW/ZZ fusion to Higgs pairs. Received: 3 March 1999 / Published online: 15 July 1999     

On the Observation Effects of Higgs Particle in e+e—→bb Z0 and tt－Z0 at LEP Ⅱ and NLC

According to the Minimal Standard Model and the Extended Standard Model with two Higgs doublets, we calculated the total cross sections and differential cross sections for the e⁺e^—→bb Z⁰ and tt－Z⁰ at the LEP Ⅱ and NLC energies in order tO study the possible observational effects of the Higgs particle. We found that the observation for the e⁺e^—→bb Z⁰ can give the information on the Higgs particle as long as the mass of the Higgs particle M_H≤140GeV. However, for the e⁺e^—→tt－Z⁰ the effect from Higgs particle will be completely suppressed by the electrowead background and cannot be observed, no matter whether the Higgs particle is heavy or light.     

Higgs production and decay with a fourth Standard-Model-like fermion generation

State-of-the-art predictions for the Higgs-boson production cross section via gluon fusion and for all relevant Higgs-boson decay channels are presented in the presence of a fourth Standard-Model-like fermion generation. The qualitative features of the most important differences to the genuine Standard Model are pointed out, and the use of the available tools for the predictions is described. For a generic mass scale of 400−600 GeV in the fourth generation explicit numerical results for the cross section and decay widths are presented, revealing extremely large electroweak radiative corrections, e.g., to the cross section and the Higgs decay into WW or ZZ pairs, where they amount to about −50 % or more. This signals the onset of a non-perturbative regime due to the large Yukawa couplings in the fourth generation. An estimate of the respective large theoretical uncertainties is presented as well.