LHT model and Higgs boson production in association with a weak gauge boson at the LHC

Considering the process pp → VH+X(V = W or Z) is a significant channel for searching for a light Higgs boson,we calculate the contributions of the littlest Higgs model with T-parity(called LHT model) to its production cross section.We find that,in most of the parameter space,the value of the relative correction parameter R is very small.However,with reasonable values of the free parameters,its value can be significantly larger.     

Single Production of Charged Gauge Boson WH^- from Left-Right Twin Higgs Model in Association with Top Quark at LHC

The twin Higgs mechanism has recently been proposed to solve the little hierarchy problem. In the context of the left-right twin Higgs （LRTH） model, we discuss single production of the new charged gauge boson WH^- , which is predicted by the left-right twin Higgs model, in association with top quark at the CERN Large Hadron Collider （LHC）. It is found that, for a typical nonzero value of mass mixing parameter M = 150 GeV in the LRTH model, the production cross section is in the range of 3 ×10^-2 - 6.07×10^3 fb at the LHC. As long as the WH^- is not too heavy, the possible signatures of the heavy charged gauge boson might be detected at the LHC experiments.     

Precise correction to parameter ρ in the littlest Higgs model

In this paper tree-level violation of weak isospin parameter, ρ in the frame of the littlest Higgs model is studied. The potentially large deviation from the standard model prediction for the ρ in terms of the littlest Higgs model parameters is calculated. The maximum value for ρ for f=1TeV, c=0.05,c′= 0.05 and υ′= 1.5GeV is ρ=1.2973 which means a large enhancement than the SM.     

Correction of the Littlest Higgs Model to Higgs Production Process e-γ→veW-H in e-γ Collisions

The littlest Higgs model is the most economical one among various little Higgs models. In the context of the littlest Higgs （LH） model, we study the process e-γ → veW^-H and calculate the contributions of the LH model to the cross section of this process. The results show that in most of the parameter spaces preferred by the electroweak precision data, the value of the relative correction is larger than 10%. Such correction to the process e-γ →veW^-H is large enough to be detected via e-γ collisions in the future high energy linear e^＋ e^- collider （ILC） experiment with the c.m. energy √s = 500 GeV and a yearly integrated luminosity ￡ = 100fb^-1, which will give an idea/way to test the model.     

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 Charged Higgs Boson Associated with Top Partner at the Large Hadron Collider

In the context of the littlest Higgs （LH） model and the left-right twin Higgs （LRTH） model, we study the production of charged Higgs boson associated with top partner at the LHC. We find that, in the LH model, its cross section can be significantly larger for the scale parameter f = 500 GeV, while sharply decreases as f increases. In the LRTH model, this production process mainly transfers to the t？tb？bb final state at the Large Hadron Collider and its production rate can reach 167.2 fb.     

Spontaneous Electro-Weak Symmetry Breaking and Cold Dark Matter

In the standard model, the weak gauge bosons and fermions obtain mass after spontaneous electro-weak symmetry breaking, which is realized by one fundamental scalar field, namely the Higgs field. We study the simplest scalar cold dark matter model in which the scalar cold dark matter also obtains mass by interaction with the weakdoublet Higgs field, in the same way as those of weak gauge bosons and fermions. Our study shows that the correct cold dark matter relic abundance within 3a uncertainty （0.093 〈 Ωdmh^2 〈 0.129） and experimentally allowed Higgs boson mass （114.4 ≤ mh≤ 208 GeV） constrain the scalar dark matter mass within 48 ≤ ms ≤ 78 GeV. This result is in excellent agreement with the result of de Boer et al. （50 ~ 100 GeV）. Such a kind of dark matter annihilation can account for the observed gamma rays excess （10σ） at EGRET for energies above 1 GeV in comparison with the expectations from conventional Galactic models. We also investigate other phenomenological consequences of this model. For example, the Higgs boson decays dominantly into scalar cold dark matter if its mass lies within 48 ~ 64 GeV.     

New Electroweak Model Without a Higgs Particle

A new unified electroweak model is proposed in this paper,In this unified electroweak model,Higgs echanism is not used.So no Higgs particle exists in the model.In order to keep the masses of intermediate gauge bosons non-zero,two sets of gauge fields will be introduced.In order to introduce symmetry breaking and to help to introduce the masses of all fileds.a vacuum potential is needed.Except for those terms concerning Higgs particle,the fundamental dynamical properties of this model are similar to those of the standard model.And in a proper limit,this model with approximately return to the standard model.The purpose of this paper is not to say that the Higgs particle does not exist in Nature,it is only to prove that,without a Higgs particle,we can also set up a unified electroweak model which is consistent with present experiments.     

Production of Charged Higgs Bosons from Left-Right Twin Higgs Model at TeV Energy e-γ Colliders

The left-right twin Higgs （LRTH） model predicts the existence of three additional Higgs bosons： one neutral Higgs φo and a pair of charged Higgs bosons φ±. In this paper, we study two pair production processes of these new particles at the next generation eγ colliders, i.e., e-γ → e-φ＋φ- , and e-γ→vRφ-φ0. We find that the production cross section of the process e-γ → e-φ＋φ- are at the level of several tens fb, the production cross section of the process e-γ→vRφ-φ0 can reach 0.35 fb with the reasonable parameter values. As long as the charged Higgs bosons are not too heavy, we conclude that these processes might be used to test for the left-right twin Higgs model in future high-energy linear collider experiments.     

Search for a neutral Higgs boson decaying to a W boson pair in pp collisions at square root of s = 1.96 TeV

We present the results of a search for standard model Higgs boson production with decay to WW*, identified through the leptonic final states e+ e- nu nu,+/-mu -/+nu nu and mu+ mu- nu nu. This search uses 360 pb -1 of data collected from pp collisions at square root of s =1.96 TeV by the upgraded Collider Detector at Fermilab (CDF II). We observe no signal excess and set 95% confidence level upper limits on the production cross section times branching ratio for the Higgs boson to WW* or any new scalar particle with similar decay products. These upper limits range from 5.5 to 3.2 pb for Higgs boson masses between 120 and 200 GeV/c2.     

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.     

Single Production of Top Quark via e-γ Collision in Left-Right Twin Higgs Model

In the context of the left-right twin Higgs （LRTH） model, we fist study single production of the standard model （SM） top quark via e-γ collisions. We find that the corrections of the LRTH model to the cross section of the process e-γ→vebt might be observed only for f ≤750 GeV and the heavy top quark mass scale M ≥500 GeV in future high energy linear e^＋e^- collider （LC） experiment with the center-of-mass （CM） energy √s = 500 GeV and a yearly integrated luminosity of ￡ = 100 fb^-1. We also consider single production of the heavy top quark T via e-γ collisions. Our numerical results show that the possible signals of the heavy top quark T might be observed via the decay channel T →Ф^＋b→tbb in future LC experiment with √s = 3 TeV and ￡ = 500 fb^-1.     

Heavy charged Higgs boson production at next generation e^\pm\gamma colliders

We assess the potential of future electron-positron linear colliders operating in the mode in detecting charged Higgs bosons with mass around and larger than the top quark mass, using Compton back-scattered photons from laser light. We compare the pair production mode, , to a variety of channels involving only one charged Higgs scalar in the final state, such as the tree-level processes ( and ) and ( and ) as well as the loop-induced channel . We show that, when the charged Higgs boson mass is smaller than or comparable to half the collider energy, , single production cross sections are of the same size as the pair production rate, whereas, for charged Higgs boson masses larger than , all processes are heavily suppressed. In general, production cross sections of charged Higgs bosons via scatterings are smaller than those induced at an collider and the latter represents a better option to produce and analyse such particles. Received: 29 August 2001 / Published online: 23 November 2001     

Associate Higgs and gauge boson production at hadron colliders in a model with vector resonances

Motivated by new models of dynamical electroweak symmetry breaking that predict a light composite Higgs boson, we build an effective Lagrangian which describes the standard model (with a light Higgs) and vector resonances. We compute the cross section for the associate production of a Higgs and a gauge boson. For some values of model parameters we find that the cross section is significantly enhanced with respect to the standard model. This enhancement is similar at the LHC (large hadron collider) and the Tevatron for the same range of resonance mass. PACS 12.60.Nz     

Higgs boson production at hadron collidersin the kT-factorization approach

We consider the Higgs boson production at high energy hadron colliders in the framework of the k_T-factorization approach. The attention is focused on the dominant gluon-gluon fusion subprocess. We calculate the total cross section and transverse momentum distributions of the inclusive Higgs production using unintegrated gluon distributions in a proton obtained from the full CCFM evolution equation. We show that k_T-factorization gives a possibility to investigate the associated Higgs boson and jets production. We calculate the transverse momentum distributions and study the Higgs-jet and jet-jet azimuthal correlations in the Higgs + one or two jet production processes. We demonstrate the importance of the higher-order corrections within the k_T-factorization approach. These corrections should be developed and taken into account in the future applications. Received: 26 January 2005, Revised: 8 July 2005, Published online: 6 October 2005     

Associated production of heavy Higgs boson with top quarks

Associated production of a heavy Higgs boson (m_H > 100 GeV) with top quarks at Juratron energies is studied. It is natural to differentiate between the “light” (2m_t < m_H < 2m_W) and “heavy” (m_H > 2m_W) Higgs search. It is assumed that the mass value of the top quarks is in the interval m_t ≈ 30–80 GeV. m_W is the W-boson mass. If m_H < 2m_W a dangerous background is given by the QCD production of four top quarks. We have calculated the cross sections for both the Higgs production and the background reaction. The disappointing result found is that the background is overwhelmingly large. However the Higgs search in this mass region is not hopeless. The associated production of the Higgs boson with a W-boson may have a clear experimental signature, its background given by the reaction $\text{p}\text{+}\text{p}\text{→}\text{W}\text{+}\text{t}\text{+}\text{t}$ might be suppressed. The difficulty with this mechanism is that the rate is rather low. If m_H > 2m_W the background is different and its contribution is expected to be small. The associated production of a Higgs boson with a pair of top quarks might be a useful method in the Higgs search in this case.     

Associated production of a light Higgs boson and a chargino pair in the MSSM at linear colliders

In the minimal supersymmetric standard model (MSSM), we study the light Higgs boson radiation off a light-chargino pair in the process at linear colliders with GeV. We analyze cross sections in the regions of the MSSM parameter space where the process cannot proceed via on-shell production and subsequent decay of either heavier charginos or the pseudoscalar Higgs boson A. Cross sections up to a few fb are allowed, according to present experimental limits on the Higgs boson, chargino and sneutrino masses. We also show how a measurement of the production rate could provide a determination of the Higgs boson couplings to charginos.Received: 24 June 2004, Revised: 13 May 2005, Published online: 19 July 2005