Probing the Lightest New Gauge Boson BH in the Littlest Higgs Model via Processes γγ→ ff^- Bg at ILC

The neutral gauge boson BH with the mass of hundreds GeV is the lightest particle predicted by the littlest Higgs （LH） model, and such particle should be the first signal of the LH model at the planed ILC if it exists indeed. In this paper, we study some processes of the BH production associated with the fermion pair at the ILC, i.e., γγ→ ff^- BH. The studies show that the most promising processes to detect BH amongγγ→ ff^- BH are γγ→ l＇^＋l＇^-BH （l＇ = e,μ）, and they can produce the sufficient signals in most parameter space preferred by the electroweak precision data at the ILC. On the other hand, the signal produced via the certain BH decay modes is typical and such signal can be easily identified from the SM background. Therefore, BH, the lightest gauge boson in the LH model, would be detectable at the photon collider realized at the ILC.     

Rare Decay B→Xsvv in the Two—Higgs—Doublet Model of Type—Ⅲ

In this paper, we calculated the new physics contribution to theoretically very clean rare decay B→X_sνν in the general two-Higgs-doublet model (model III). Within the considered parameter space, we found that (a) the new physics contribution can provide one to two orders of enhancement to the branching ratio B(B→X_sνν) and can saturate the experimental bound on B(B→X_sνν) in some regions of the parameter space; (b) besides the CLEO data of B→X_sγ, the ALEPH upper limit on B(B→X_sνν) also leads to further constraint on the size of the Yukawa coupling λ_tt: λ_tt< 6.4 for λ_bb=2.7 and m_H⁺=200 GeV.     

在LEPⅡ及NLC能量下e~＋e~－→b_b~－Z~0和t_t~－Z~0过程中Higgs粒子的观测效应

根据最小标准模型及双Ｈｉｇｇｓ二重态的扩展标准模型理论，计算了ＬＥＰⅡ以及ＮＬＣ能量下ｅ＋ｅ－→ｂＺ０和ｔＺ０的总截面和微分截面以探求Ｈｉｇｇｓ粒子的观测效应．我们发现，只要Ｈｉｇｇｓ粒子的质量ＭＨ≤１４０ＧｅＶ，对ｅ＋ｅ－→ｂＺ０的测量就能清楚地提供Ｈｉｇｇｓ粒子的信息．然而对ｅ＋ｅ－→ｔＺ０，不论Ｈｉｇｇｓ粒子是轻或重，它的效应都被淹没在弱电过程的本底中，没有观测的可能．     

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.     

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.     

B→ X8γ, X8l＋l- Decays and Constraints on Mass Insertion Parameters in MSSM

In this paper, we study the upper bounds on the mass insertion parameters （δAB^q）ij in the minimal super symmetric standard model. We found that the information from the measured branching ratio of B→ X8γ, X8l＋l- decay can help us to improve the upper bounds on the mass insertions parameters （δAB^u,d）3j,i3 Some regions allowed by the data of Br（B→ X8γ） are excluded by the requirement of an SM-like C7γ （rnb） imposedby the data of Br（B→ X8γ, X8l＋l- ）.     

The Effects from the Complex Parameters on t→ch^0 Within the Minimal Supersymmetric Standard Model

We investigate the effects from complex parameters on the branching ratio (BR) of the flavor changing rare decay t→ch^0 contributed by the electroweak interactions in the framework of the minimal supersymmetric standard model with complex parameters. We study the dependence of the BR on the possible relevant additional parameter swhich could be the originalsources inducing CP-violation, i.e., the complex phase angles φμ and φAb in squark and chargino sectors and δ13 appearing in Cabibbo-Kobayashi-Maskawa matrix. We find that these parameters influence the BR obviously and the effects induced by φμ and φAb are much larger than by δ13. With the different chosen values of the complex parameters, the BR is in the range between 10^-10 and 10^-8, depending mainly on the phase angles of the higgsino mass parameter μ and the trilinear coupling Ab.     

在LEPⅡ及NLC能量下e+e—→bb Z0 和 tt－Z0过程中Higgs粒子的观测效应

根据最小标准模型及双Higgs二重态的扩展标准模型理论,计算了LEPⅡ以及NLC能量下e⁺e^—→bb Z⁰ 和 tt－Z⁰的总截面和微分截面以探求Higgs粒子的观测效应.我们发现,只要Higgs粒子的质量M_H≤140GeV,对e⁺e^—→bb Z⁰的测量就能清楚地提供Higgs粒子的信息.然而对e⁺e^—→tt－Z⁰,不论Higgs粒子是轻或重,它的效应都被淹没在弱电过程的本底中,没有观测的可能.     

Tau Leptonic Decay τ→lVlVτ in Littlest Higgs Model＊

We consider the τ leptonic decay $\tau\rightarrow l\bar{\nu}_{l}\nu_{\tau}$ in the framework of the littlest Higgs (LH) model and calculate the corrections of new particles to this decay. We find that the contributions of the charged scalars can be safely ignored and the LH model is in perfect agreement with the universality of the couplings of the SU gauge bosons to the leptonic charged currents. The corrections of the LH model to the τ leptonic decay $\tau\rightarrow l\bar{\nu}_{l}\nu_{\tau}$ are not sensitive to the parameter c, but depend strongly on the parameters f and x. The precision measured data about the τ leptonic decay demand that the parameter f approximately equal 3.5 TeV and x>0.1, while agree with the general expectation based on other phenomenological explorations.     

大型强子对撞机上的CMS探测器

CMS探测器是大型强子对撞机(LHC)上的4个实验之一,它的设计思想是在质心能量为14TeV及积分亮度为1034cm-2s-1的条件下对质子-质子对撞进行研究.它的特点是非常紧凑,其μ子室几乎覆盖了4π立体角.另外,CMS探测器还有可提供超强磁场的超导磁铁和由超导磁铁环绕的径迹室以及电磁量能器和强子量能器.CMS探测器对于末态为电子、光子、特别是μ子的物理过程有很好的测量精度.     

Probing the Stau-Stau-Higgs Couplings in the MSSM at NLC

In the minimal supersymmetric standard model (MSSM) with CP violating phases, this paper discussesthe production of the lightest neutral Higgs boson in association with tau sleptons at future high-energy e e- linearcolliders. In parameter space of the constrained MSSM, the production cross section of e e- → h0τ1 τ1- can be verysubstantial at high energies. This process would provide a production mechanism for probing couplings of neutral Higgsbosons to tau sleptons as well as some soft supersymmetric breaking parameters at next linear colliders.     

Distinguishing a SM-like MSSM Higgs boson from SM Higgs boson at muon collider

We explore the possibility of distinguishing the SM-like MSSM Higgs boson from the SM Higgs boson via Higgs boson pair production at future muon collider. We study the behavior of the production cross-section in SM and MSSM with Higgs boson mass for various MSSM parameters tan β and m _A . We observe that at fixed CM energy, in the SM, the total cross-section increases with the increase in Higgs boson mass whereas this trend is reversed for the MSSM. The changes that occur for the MSSM in comparison to the SM predictions are quantified in terms of the relative percentage deviation in cross-section. The observed deviations in cross-section for different choices of Higgs boson masses suggest that the measurements of the cross-section could possibly distinguish the SM-like MSSM Higgs boson from the SM Higgs boson.      

Charged Higgs Boson Pair Production via Gluon-Gluon Collisions in MSSM with CP Violation

The CP-violating effects to the subprocess gg → H H- are studied in the mSUGRA scenario at the CERN large hadron collider, by taking into account the experimental bounds of electron and neutron electric dipole moments.The CP-violating effects in this process are related to the complex phases ofμ and Af in the mSUGRA scenario. In our calculation we consider smallCP phases ofμ and Af and neglect the effects of neutral Higgs boson mixing. In this case the CP effects to the process mainly come from the complex couplings of Higgs-squark-squark. We find a strong dependence of charged Higgs boson pair production rate on the complex couplings in the parameter space of minimal supersymmetric standard model``     

Charged Higgs Boson Pair Production via Gluon-Gluon Collisions in MSSM with CP Violation

The CP-violating effects to the subprocess gg→H⁺H^- are studied in the mSUGRA scenario at the CERN large hadron collider, by taking into account the experimental bounds of electron and neutron electric dipole moments. The CP-violating effects in this process are related to the complex phases of μ and A_f in the mSUGRA scenario. In our calculation we consider small CP phases of μ and A_f and neglect the effects of neutral Higgs boson mixing. In this case the CP effects to the process mainly come from the complex couplings of Higgs-squark-squark. We find a strong dependence of charged Higgs boson pair production rate on the complex couplings in the parameter space of minimal supersymmetric standard model.     

The Effect of Slepton Flavor Mixing on the Mass of SM-like Higgs Boson in the MSSM

We investigate the one-loop contributions to the mass of the SM-like Higgs boson in the MSSM considering the effect of slepton flavor mixing, which is parametrized by the dimensionless parameter δXY(X, Y = L, R) in the slepton mass matrices. For the surviving samples under the experimental constraints, we calculate the corrections to the mass of the SM-like Higgs boson in terms of δXY. We find that the mass correction ?mhcan even be larger than 10 GeV for large δRLor δLR. Moreover, ?mhhas strong sensitivity to δRLor δLR, while the weak sensitivity to δLLor δRR, sinceδRLor δLRenters directly into the coupling of Higgs boson with sleptons in the calculations of Higgs boson self-energies.     

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.     

The Effect of Slepton Flavor Mixing on the Mass of SM-like Higgs Boson in the MSSM

We investigate the one-loop contributions to the mass of the SM-like Higgs boson in the MSSM considering the effect of slepton flavor mixing, which is parametrized by the dimensionless parameter δ_XY (X,Y=L,R) in the slepton mass matrices. For the surviving samples under the experimental constraints, we calculate the corrections to the mass of the SM-like Higgs boson in terms of δ_XY. We find that the mass correction Δm_h can even be larger than 10 GeV for large δ_RL or δ_LR. Moreover, Δm_h has strong sensitivity to δ_RL or δ_LR, while the weak sensitivity to δ_LL or δ_RR, since δ_RL or δ_LR enters directly into the coupling of Higgs boson with sleptons in the calculations of Higgs boson self-energies.     

Higgs and SUSY searches at future colliders

In this talk, I discuss some aspects of Higgs searches at future colliders, particularly comparing and contrasting the capabilities of LHC and next linear collider (NLC), including the aspects of Higgs searches in supersymmetric theories. I will also discuss how the search and study of sparticles other than the Higgs can be used to give information about the parameters of the minimal supersymmetric Standard Model (MSSM).     

Universal soft terms in the MSSM on D-branes

In Type II string vacua constructed from intersecting/magnetized D-branes, the supersymmetry-breaking soft terms are genericaly non-universal. It is shown that universal supersymmetry-breaking soft terms may arise in a realistic MSSM constructed from intersecting/magnetized D-branes in Type II string theory. For the case of dilaton-dominated supersymmetry breaking, it is shown that the universal scalar mass and trilinear coupling are fixed such that _m0=(1/2)_m3/2$m_0=(1/2)m_{3/2}$ and _A0=−_m1/2$A_0=-m_{1/2}$. In addition, soft terms where the universal scalar mass _m0$m_0$ is much larger than the universal gaugino mass _m1/2$m_{1/2}$ may be easily obtained within the model. Finally, it is shown that the special dilaton and no-scale strict moduli boundary conditions, which are well known in heterotic string constructions, may also be obtained.     

Higgs physics at future colliders: Recent theoretical developments

I review the physics of the Higgs sector in the standard model and its minimal supersymmetric extension, the MSSM. I will discuss the prospects for discovering the Higgs particles at the upgraded Tevatron, at the large hadron collider, and at a future high-energye ⁺ e ⁻ linear collider with centre-of-mass energy in the 350–800 GeV range, as well as the possibilities for studying their fundamental properties. Some emphasis will be put on the theoretical developments which occurred in the last two years.