Research of bb Production in the Topcolor Assisted Technicolor Model

In the framework of topcolor assisted technicolor (TC2) model, we calculate the contributions of cross section from the pseudo Goldstone bosons and new gauge bosons to e⁺e^－ →bb. We find that, within reasonable ranges of the parameters, the corrections arising from technipions and new gauge bosons are negligibly small; and the top pions afford dominate contribution, the maxim cross section corrections can reach 43% with the c.m. energy √s=500GeV; whereas in case of √s=1500GeV, the maxim cross section relative corrections is only 3.1%. It might open a window to detect topcolor assisted technicolor model in the experiment of next generation linear collider.     

Top Quark Pair Production at e^＋e^— Colliders in the Topcolor—Assisted Technicolor Model

In the framework of topcolor-assisted technicolor model we calculate the contributions from the preudo Goldstone bosons and new gauge bosons to e^ e^-→ttk.We find that for reasonable ranges of the parameters,the preudo Goldstone bosons afford dominate contribution,the correction arising from new gauge bosons is negligibly small,the maximum of the relative corrections is-10% with the center-of-mass energy √s=500GeV;whereas in the case of √s=1500 GeV,the relative corrections could be up to 16%.Thus large new physics might be observable at the experiments of next-generation linear colliders.     

Search for new particles decaying to t&tmacr; in p&pmacr; collisions at radicals = 1.8 TeV

We use 106 pb (-1) of data collected with the Collider Detector at Fermilab to search for narrow-width, vector particles decaying to a top and an antitop quark. Model independent upper limits on the cross section for narrow, vector resonances decaying to t&tmacr; are presented. At the 95% confidence level, we exclude the existence of a leptophobic Z' boson in a model of top-color-assisted technicolor with mass M(Z')<480 GeV/c(2) for natural width gamma = 0.012M(Z'), and M(Z')<780 GeV/c(2) for gamma = 0.04M(Z').     

More supersymmetric technicolor

We propose a supersymmetric model of particle physics in which supersymmetry is broken by strong gauge forces. Unlike previous realistic supersymmetric technicolor theories, the model contains only one extra strong gauge group, and it lends itself readily to grand unification. The model also has no light axions which can burn out stars. A variety of new particles, many weighing less than 100 GeV, are predicted. A no-go theorem due to Witten is discussed.     

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     

Searches at HERA for squarks in R-parity violating supersymmetry

A search for squarks in R-parity violating supersymmetry is performed in collisions at HERA at a centre of mass energy of 300 GeV, using H1 data corresponding to an integrated luminosity of 37 pb. The direct production of single squarks of any generation in positron-quark fusion via a Yukawa coupling is considered, taking into account R-parity violating and conserving decays of the squarks. No significant deviation from the Standard Model expectation is found. The results are interpreted in terms of constraints within the Minimal Supersymmetric Standard Model (MSSM), the constrained MSSM and the minimal Supergravity model, and their sensitivity to the model parameters is studied in detail. For a Yukawa coupling of electromagnetic strength, squark masses below 260 GeV are excluded at 95% confidence level in a large part of the parameter space. For a 100 times smaller coupling strength masses up to 182 GeV are excluded. Received: 28 February 2001 / Published online: 29 June 2001     

Technihadron production and decay at LEP2

The simple “straw-man” model of low-scale technicolor contains light color-singlet technihadrons, which mix with the electroweak gauge bosons. We present lepton collider production rates at the parton level, and show that experiments at LEP2 may be sensitive to the presence of technirho and techniomega states with masses 10–20 GeV beyond the center-of-mass energy because of the mixing. The exact sensitivity depends on several parameters, such as the technipion mass, the technipion mixing angle, and the charge of the technifermions. In an appendix, we describe the implementation of the model into the event generator PYTHIA for particle-level studies at lepton and hadron colliders.     

Quantum weakdynamics as an SU(3)_I gauge theory: Grand unification of strong and electroweak interactions

Quantum weakdynamics (QWD) as an gauge theory with the vacuum term is considered to be the unification of the electroweak interaction as an gauge theory. The grand unification of beyond the standard model is established by the group . The grand unified interactions break down to weak and strong interactions at a new grand unification scale, GeV, through dynamical spontaneous symmetry breaking (DSSB); the weak and strong coupling constants are the same, , at this scale. DSSB is realized by the condensation of scalar fields, postulated to be spatially longitudinal components of gauge bosons, instead of Higgs particles. Quark and lepton family generation, the Weinberg angle , and the Cabbibo angle are predicted. The electroweak coupling constants are , , , and ; there are symmetric isospin interactions. Received: 21 January 2001 / Published online: 21 November 2001     

Search for resonant tt[overline] production in pp[overline] collisions at sqrt[s]=1.96 TeV

We report on a search for narrow-width particles decaying to a top and antitop quark pair. The data set used in the analysis corresponds to an integrated luminosity of 680 pb(-1) collected with the Collider Detector at Fermilab in run II. We present 95% confidence level upper limits on the cross section times branching ratio. Assuming a specific top-color-assisted technicolor production model, the leptophobic Z' with width Gamma(Z')=0.012M(Z'), we exclude the mass range M(Z')<725 GeV/c(2) at the 95% confidence level.     

A measurement of the QCD colour factors using event shape distributions at \sqrt{s}=14 to 189 GeV

Measurements of the QCD colour factors and and of the number of active quark flavours in the process at high energy are presented. They are based on fits of +NLLA QCD calculations to distributions of the event shape observables and measured at centre-of-mass energies from 14 GeV to 189 GeV. Hadronisation effects are approximated with power correction calculations which also depend on the QCD gauge structure. In this approach potential biases from hadronisation models are reduced. Our results for individually measured quantities obtained from and C are in good agreement with QCD based on the SU(3) symmetry group where for the energies considered here, and . From simultaneous fits of and with and C we find which is also in good agreement with the QCD expectation. Received: 3 May 2001 / Revised version: 22 June 2001 / Published online: 3 August 2001     

Generations of massless composite quarks and leptons

We present a QCD-like composite model in which quarks, leptons and technifermions are three-body systems made out of three kinds of massless elementary fermions t, c and w, each carrying technicolor, color and weak gauge interactions, respectively. Discrete symmetries, remnants of the U(1)_A of the original lagrangian, are responsible for the masslessness of all the quarks and leptons and give the precise meaning of the generations. The model exhibits three generations for both quarks and leptons. Small but non-zero masses of the quarks and leptons are produced by the technicolor condensate of the composite technifermions, which thereby leads to the non-trivial Cabibbo mixing. Proton decays are all forbidden at the mass scale of the QCD-like theory.     

Associated production of a neutral top-Higgs with a heavy-quark pair in the γγ collisions at ILC

We have studied the associated production processes of a neutral top-Higgs in the topcolor assisted technicolor model with a pair of heavy quarks in γγ collisions at the International Linear Collider (ILC). We find that the cross section for ttht in γγ collisions is at the level of a few fb with the c.m. energy √s=1000 GeV, which is consistent with the results of the cross section of ttH in the standard model and the cross section of tth in the minimal supersymmetric standard model. It should be clear that hundreds of to thousands of ht per year can be produced at the ILC. This process of γγ→ttht is really interesting in testing the standard model and searching the signs of technicolor.     

Dynamical symmetry breaking of extended gauge symmetries

We construct asymptotically free gauge theories exhibiting dynamical breaking of the left-right gauge group G(LR)=SU(3)(c) x SU(2)(L) x SU(2)(R) x U(1)(B-L), and its extension to the Pati-Salam gauge group G(422)=SU(4)(PS) x SU(2)(L) x SU(2)(R). The models incorporate technicolor for electroweak breaking, and extended technicolor for the breaking of G(LR) and G422 and the generation of fermion masses. They include a seesaw mechanism for neutrino masses, without a grand unified theory (GUT) scale. These models explain why G(LR) and G422 break to SU(3)(c) x SU(2)(L) x U(1)(Y), and why this takes place at a scale (approximately 10(3) TeV) large compared to the electroweak scale, but much smaller than a GUT scale.     

New formulas and predictions for running fermion masses at higher scales in SM, 2HDM, and MSSM

Including contributions of scale-dependent vacuum expectation values, we derive new analytic formulas and obtain substantially different numerical predictions for the running masses of quarks and charged leptons at higher scales in the SM, 2HDM and MSSM. These formulas exhibit significantly different behaviours with respect to their dependence on gauge and Yukawa couplings from those derived earlier. At one-loop level, the masses of the first two generations are found to be independent of the Yukawa couplings of the third generation in all three effective theories in the small mixing limit. Analytic formulas are also obtained for the running of in 2HDM and MSSM. Other numerical analyses include a study of the third generation masses at high scales as functions of the low-energy values of and the SUSY scale GeV. Received: 1 October 2000 / Revised version: 11 January 2001 / Published online: 12 April 2001     

Detecting Extended Technicolor Effects via the Process e^＋e^—→tt^— at High Energy e^＋e^—,Linear Collider

We calculate the corrections of extended technicolor(ETC) interactions to the asymmetry parameter ALR and the polarized parameters PL^t,PR^t of the process e^ e^-→tt- in topcolor-assisted multiscale technicolor model.our results show that the ETC efect effect on PR^t in negligibly small which can be safely ignored,and the ETC effect on ALR may be testable at high energy e^ e^- linear collider(LC),FOr 0.03≤ε≤0.1,500GeV≤s○800GeV,the relative correction of PL^t is in the range of 15%≤δPL^t/PL^t,SM≤39%,which will certainly be detected at the LC experiments(for example TESLA).     

The Process e+e-→tc in Technicolor Model with a Massless Scalar Doublet

At LEPⅡ (the energy: √s = 200 GeV), we carry out precise calculations on the process e⁺e^-→tc in the framework of technicolor model with a massless scalar doublet. The results show that the process is unmeasurably small in this TC model.     

人工色动力学对Wb耦合的修正

考虑了一代人工色（ＯＧＴＣ）模型和ｔｏｐｃｏｌｏｒ援助的多标度人工色（ＴＯＰＣＭＴＣ）模型中的规范玻色子对Ｗｔｂ耦合的贡献。发现对角ＥＴＣ玻色子的交换对Ｗｔｂ耦合没有直接贡献，运用ＬＥＰ给出的Ｒｂ的数值，发现对于一定范围内的参数值来说，ＯＧＴＣ模型中的ＥＴＣ规范玻色子交换和ＴＯＰＣＭＴＣ模型中的ＥＴＣ规范玻色子交换和ｃｏｌｏｒｎ交换对ＣＫＭ矩阵元Ｖｔｂ的贡献都是相当大的，Ｖｔｂ可能被费米实验室ＴｅｖａｔｒｏｎＲｕｎ３探测到。     

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.     

Search for gauge mediated SUSY breaking topologies in ee collisions at centre-of-mass energies up to 209 GeV

A total of 628 bp^-1 of data collected with the ALEPH detector at centre-of-mass energies from 189 to 209 GeV is analysed in the search for gauge mediated SUSY breaking (GMSB) topologies. These topologies include two acoplanar photons, non-pointing single photons, acoplanar leptons, large impact parameter leptons, detached slepton decay vertices, heavy stable charged sleptons and multi-leptons plus missing energy final states. No evidence is found for new phenomena, and lower limits on masses of supersymmetric particles are derived. A scan of a minimal GMSB parameter space is performed and lower limits are set for the next-to-lightest supersymmetric particle (NLSP) mass at 54 GeV/c² and for the mass scale parameter at 10 TeV/c², independently of the NLSP lifetime. Including the results from the neutral Higgs boson searches, a NLSP mass limit of 77 GeV/c² is obtained and values of up to 16 TeV/c² are excluded. Received: 14 March 2002 / Published online: 20 September 2002