The Higgs Boson Mass in MSM and the New Data

In this paper we study the implications of the top quark mass measurement at CDF for the Higgs boson mass M_H. We find that the present data are most likely in favor of heavy Higgs boson, M_H = 340_-270⁺⁷⁷⁰ GeV for M_t = 174 GeV, but no realistic constraints on M_H could be derived until the measurement of M_t reaches high precision.     

Higher order QCD and quark mass corrections to the Z widths in the standard model

We estimate, in the scheme, the strenghts of the higher order QCD (_s², _s³) and quark mass (m_f², m_f⁴, _s(m_f², m_f⁴)) corrections to the Z widths in the standard model (SM). Then, we give improved SM predictions of these widths. The observables Γ_H/Γ_e and σ_H, which can be predicted and measured accurately are almost insensitive to the changes of the Higgs ( 40 GeV M_H 1 TeV) and top quark (M_zM_t230 GeV) masses. Then, they should be useful in the high precision tests of the SM> Improved estimates of some quantities related to the width which are sensitive to the top quark mass are also given.     

Corrections to Zbb Vertex from Heavy PG Bosons and Phenomenology

In the framework of one generation technicolor model we calculated the virtual effects from heavy PG bosons to the Zbb vertex. Within parameter space the largest reduction from thk charged PGB's and top quark to the partial width Γ_b was 71 MeV while the maximum correction to the branching ratio R_b was about 14%. From the comparison of theoretical. predictions with the corresponding data we are able to put an "primary" upper bound on the mass of P₈^±: M_p2 < 280 GeV for given M_t = 200 GeV.     

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.     

Four-Generation Condensate Scheme Without the Fourth Generation of Leptons

The renormalization group (RG) analyses show that in the four-generation fermion condensate scheme of electroweak symmetry breaking without the extra fourth generation of leptons thelimitation to the compositeness scale Λ could be greatly loosened and up to Λ<10¹⁰ GeV if the masses of the extra fourth generation of quarks are demanded to be bigger than the topquark mass m_t = 180 GeV. However, the mass constraints 2(m_Q)_minh⁰<2(m_Q)_max between the Higgs boson h⁰ and its constituent Q-fermions are no longer totally valid for Λ>10⁵ GeV. The ~redicted masses of the fourth generation of quarks and the Higgs boson will be larger than the corresponding ones in the four-generation quark-lepton scheme. The stability of the results for variation of the compositeness boundary conditions could be explained more clearly.     

Ba（d）^o-Ba（d）^o Mixing and New Physics Effects in a Top Quark Two-Higgs Doublet Model

We calculate the new physics contributions to the neutral Bd^o and Ba^o meson mass splitting △Md and △Ma induced by the box diagrams involving the charged-Higgs bosons in the top quark two-Higgs doublet model （T2HDM）. Using the precision data, we obtain the bounds on the parameter space of the T2HDM： （a） For fixed MH = 400 GeV and 5= [0°, 60°], the upper bound on tan β is tan β≤ 30 after the inclusion of major theoretical uncertainties; （b） For the case of tan β≤ 20, a light charged Higgs boson with a mass around 300 GeV is allowed; and （c） The bounds on tan β and MH are strongly correlated： a smaller （larger） tan β means a lighter （heavier） charged Higgs boson.     

The Mass Bounds on Exotic Particles in an SU(3)L×U(1)X Model

We study an SU(3)_L×U(1)_X electroweak model. By requiring M²_Z1-M²_W/cos²θ_W to be less than experimental value we obtain a lower bound on Z' boson mass, M_Z' >600 GeV. The relation between M_Z' and M_U (M_V) then gives a lower bound on M_U (M_V):M_U (M_V)>490 GeV. From the constraint sin² θ_W(M_Z')<0.3, the upper bounds on M_Z' and M_U (M_V) are computed to be M_Z'<5.8×10⁴ TeV and M_U (M_V)<4.6×10⁴ TeV. We estimate further the K_L-K_S mass difference due to Z' exchange and try to use the result to obtain stronger lower bounds. On cosmological grounds we find that M_N<390 eV for T_f=2.3 GeV and M_N<740 eV for T_f=300 GeV.     

An Improved Perturbative Expression for the Pion Form Factor with Sudakov Suppression

We present an improved perturbative expression for the pion form factor with Sudakov suppression, in which the running coupling constant is suggested to be frozen at α_s, (T>) and the intrinsic transverse momentum dependence associated with pion wavefunction is re-analysed. This expression is available for momentum transfer of the order of a few GeV as wed as for Q→∞. Our scheme can be extended to evaluate contributions to the pion form factor beyond the leading order.     

A Study on the Exciton-Ionized-Donor Complex Bound to the Surface of a Nonpolar Semiconductor

The exciton-ionized-donor complex with the donor on the surface of a semiconductor (X, D⁺)_s. is investigated for the first time. The binding energy of the complex is calculated variationally as a function of the effective mass ratio of the electron to the hole σ, and high-frequency dielectric constant ε_∞ of the host semiconductor occupying the semi-infinite space. The infinite potential barrier approximation, Levine wave function and the effective-mass approximation are used for the electron and the hole. The image potentials are also used to take into account the surface charge induced by the electron or the hole when it is near the surface. The results are presented graphically without any restrict of individual material. It is found that no unstable range of σ appears for (X, D⁺)_s.     

Spin correlations at the Z peak. A probe to the Z′ mass

The interactions of a new heavy gauge boson are fixed by its coupling to matter and by its mass and its mixing with the Z⁰. Until now LEP has only constrained the Z′ mixing. However, there is one observable (and only one), the P- and T-odd transverse-normal spin correlation in ττ production, which fully and independently of its mixing measures the Z′ mass at the Z peak. For M_z′ 130 GeV the Z′ contribution to this observable is typically of the same order as the standard model contribution.     

Biphasic behavior of energy in a stepped chain

The impact energy decay in a step-up chain containing two sections is numerically studied.There is a marked biphasic behavior of energy decay in the first section.Two sections close to the interface are in compression state.The degree of compression of the first section first decreases and becomes weakest at "crossing" time of biphasic behavior of energy,then increases.The further calculations provide the dependence of the character time on mass ratio(m1/m2),where m1 and m2are the particle mass in the first and second section respectively.The bigger the α(α = [(? m_1-m_2)/(? m_1+ m_2)]~2 with? = 1.345),the bigger the energy ratio is.The multipulse structure restricts the transport of energy.     

Equilibrium dynamics of the sub-Ohmic spin-boson model under bias

Using the bosonic numerical renormalization group method, we studied the equilibrium dynamical correlation function C(ω) of the spin operator σ_z for the biased sub-Ohmic spin-boson model. The small-ω behavior C(ω) ∝ω~s is found to be universal and independent of the bias ε and the coupling strength α(except at the quantum critical point α = αc and ε = 0). Our NRG data also show C(ω) ∝χ~2ω~s for a wide range of parameters, including the biased strong coupling regime(ε = 0 and α α_c), supporting the general validity of the Shiba relation. Close to the quantum critical point αc,the dependence of C(ω) on α and ε is understood in terms of the competition between ε and the crossover energy scale ω_0~*of the unbiased case. C(ω) is stable with respect to ε for ε《ε~*. For ε》ε~*, it is suppressed by ε in the low frequency regime. We establish that ε~*∝(ω_0~*)~(1/θ)holds for all sub-Ohmic regime 0≤s 1, with θ = 2/(3s) for 0 s≤1/2 and θ = 2/(1 + s) for 1/2 s 1. The variation of C(ω) with α and ε is summarized into a crossover phase diagram on the α–ε plane.     

Top Quark,Heavy Fermions and the Composite Higgs Boson

We study the properties of heavy fermions in the vector-like representation of the electroweak gauge group SU(2)_W×U(1)_Y with Yukawa couplings to the standard model Higgs boson. Applying the renormalization group analysis, we discuss the effects of heavy fermions to the vacuum stability bound and the triviality bound on the mass of the Higgs boson. We also discuss the interesting possibility that the Higgs particle is composed of the top quark and heavy fermions. The bound on the composite Higgs mass is estimated using the method of Bardeen, Hill and Lindner (Phys. Rev. D 41 (1990) 1647), 150 GeV ≤ m_H ≤ 450 GeV.     

The Rare DecayK+ →π+vv and Effects of Charged Technipions

In this paper we calculate the contributions to the FCNC rare decay from the charged technipion P^± and P₈^± in the frarnervork of technicolor theory. We find that: (a) P^± can provide a positive but relatively small contribution to the process; (b) the contribution is large and positive for relatively light P₈^± and becomes negative for m_p8 ≥ 531 GeV; (c) the enhancement to the ratio BR() can be as large as a factor of 30 for m_p1 = 50 GeV and m_p8 = 100 GeV; (d) the lower mass bound on m_p8 is m_p8 > 220,190 GeV for m_p1 = 50,200 GeV, respectively     

Properties of the proposed τ charged lepton

The anomalous eμ and 2-prong μx events produced in e⁺e⁻ annihilation are used to determine the properties of the proposed τ charged lepton. We find the τ mass is 1.90 ± 0.10 GeV/c²; the mass of the associated neutrino, ν_τ, is less than 0.6 GeV/c² with 95% confidence; V - A coupling is favored over V + A coupling for the τ − ν_τ current; and the leptonic branching ratios are 0.186 ± 0.010 ± 0.028 from the eμ events and 0.175 ± 0.027 ± 0.030 from the μx events where the first error is statistical and the second is systematic.     

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.     

纳米SrHPO4：RE（RE=Eu3+或Tb3+）磷光体的水热合成与光谱特性

利用水热法合成了α-SrHPO₄：RE（RE=Eu³⁺,Tb³⁺）纳米磷光体,并研究了材料的形貌与光谱特性。α-SrHPO₄纳米粒子为长度90~200 nm的棒状结构,直径为24~36 nm。Eu³⁺和Tb³⁺的掺杂均会降低α-SrHPO₄的结晶度,并减小其长径比。α-Sr_0.97HPO₄：0.03Eu³⁺在395 nm近紫外光的激发下,存在分别由⁵D₀→⁷F₁和⁵D₀→⁷F₁₂跃迁引起的590 nm和614 nm发射峰,最终发射橙红光。α-Sr_0.97HPO₄：0.03Tb³⁺在217 nm近紫外光的激发下,存在由⁵D₄→⁷F₅跃迁引起的543 nm绿光发射。     

ON THE NEUTRINO MASS,THE ABUNDANCE OF RIGHT-HANDED NEUTRINO AND THE CLOSENESS OF THE UNIVERSE

We point out that although the neutrino mass is finite,the left-handed neutrino density still dominates over the righthanded one in the universe unless there exists one or more elementary fernions (quark or lepton) whose mass is larger than 10⁶ GeV. or M_WR/M_WL≤10². (M_WLand M_WR are the left and right handed intermediate boson respectively.If there exists neutrino the mass of which is about 34 ev. as indicated in some experiments, then one can conclude that the total neutrino mass of the universe s,bvld contribute abput 99%. to the whole masses and lead to the closeness of the universe.This conclusion can be brought to the agreement of all observation datd which have been-obtained so far. A mass limit of all species of neutrinos obtained by reexamining all data is ≤ 200 eV.     

Composite scalars in ee collisions and radiative Z decays

Starting point is the hypothesis that the observed Z→e⁺e⁻γ decays are mediated by a (composite) spin 0 boson X with 40m_X50 GeV. The consequences for e⁺e⁻→e⁺e⁻, e⁺e⁻→γγ and e⁺e⁻→ hadrons at PETRA are explored. PETRA experiments turn out to be sensitive up to masses m_X50 GeV; the best indicator for m_X 48 GeV is the angular distribution of Bhabha scattering.     

Rashba自旋-轨道相互作用影响下量子盘中强耦合磁极化子性质的研究

本文基于Lee-Low-Pines幺正变换法,采用Tokuda改进的线性组合算符法研究了Rashba自旋-轨道相互作用效应下量子盘中强耦合磁极化子的性质.结果表明,磁极化子的相互作用能Eint的取值随量子盘横向受限强度ω0、外磁场的回旋频率ωc、电子-LO声子耦合强度α和量子盘厚度L的变化均与磁极化子的状态性质密切相关;磁极化子的平均声子数N随ωc,ω0和α的增加而增大,随L的增加而振荡减小;在Rashba自旋-轨道相互作用效应影响下磁极化子的有效质量将劈裂为m*+,m*-两种,它们随ωc,ω0和α的增加而增大,随L的增加而振荡减小;在研究量子盘中磁极化子问题时,电子-LO声子耦合和Rashba自旋-轨道相互作用效应的影响不可忽略,但Rashba自旋-轨道相互作用和极化子效应对磁极化子的影响只有在电子运动的速率较慢时显著.