W boson pair production at heavy Z resonance

In theories with an extra U(1) gauge boson (Z₂) at low energy, W boson pairs may be produced copiously by the process e⁺e⁻ → Z₂ → W⁺W⁻, at the Z₂ resonance. We calculate the cross section for this process, and find that it could be 1 to 2 orders of magnitude bigger than the conventional nonresonant process e⁺e⁻ → W⁺W⁻ via γ, Z and ν exchanges.     

Transverse momentum in Drell-Yan processes

We study the transverse momentum distribution of muon pairs from Drell-Yan processes in QCD. In particular the dependence of 〈k_⊥²〉 on Q² is considered. QCD predicts an approximately linear rise of 〈k_⊥²〉 with S or Q² only at fixed τ = Q²/S. The slope as a function of τ is quantitatively studied for P$\text{P}$ and P-nucleus scattering. The most recent data showing a rather flat 〈k_⊥²〉 in Q² at fixed S are found to be consistent with QCD.     

Higgs boson production by W and Z collisions

A general formulation for the WW → H and ZZ → H mechanisms of heavy Higgs boson production in hadron colliders is presented. The known results in the effective W approximation are obtained from the quark-parton model limit of the double inelastic scattering configuration. In addition contributions from the elastic scattering configurations and from α_s-processes of QCD are estimated.     

W pair production by Z0 pair fusion

Using the effective gauge boson approximation we calculate the invariant mass distribution and longitudinal polarization fraction for the production of W⁺W⁻ pairs by Z⁰ pair fusion at a collider energy of 40 TeV. The mass distribution is compared with the case where the production is by W⁺W₋ pair fusion. Results are presented for Higgs masses of 0.5 and 1 TeV.     

Z boson pair production and compositeness at large hadron colliders

Z boson pair production at LHC and SSC provides an opportunity to study possible effects due to compositeness in a very high energy domain. We discuss several sources of anomalous effects and give the corresponding bounds on the appropriate compositeness scale. The best bounds are obtained for contact interactions implying longitudinal components of theZ's and for the anomalous couplings of three neutral vector bosons.     

Transverse momentum distribution of lepton-pairs in Drell-Yan process in an asymptotically free scalar field theory

The transverse momentum dependence of the parton distribution function and the Drell-Yan cross section is studied in detail in the asymptotically free scalar field theory in six dimensions. In the context of the renormalization group approach of Collins, particular attention is devoted to the transition between the small q_T formula (due to multe-quanta effects) and the large q_T formula (due to single hard-quantum emission). The calculation represents a case study of the application of the renormalization group method and provides a guide to the corresponding study in QCD.     

ILC上Z玻色子与荷电top-pion对联合产生过程的研究

在国际直线对撞机(ILC)上顶色辅助的人工色(TC2)模型下对Z玻色子与荷电top-pion对联合产生过程e⁺e^- → Zπ_t⁺π_t^-进行了研究. 计算了过程e⁺e^- → Zπ_t⁺π_t^-的产生截面, 发现在TC2模型所允许的参数空间范围之内该过程的截面最大可达到1 fb. 考虑到荷电top-pion的主要的衰变模式π_t⁺ → tb, 发现该截面在ILC能产生很可观的事例数.     

W ± boson pair production ine + e − process

I discuss the determination ofW ^± boson mass by the total cross-section ofe ⁺ e ^?→W⁺W^? process and its relation to tests of the electroweak higher order effects. In order to get rid of the confusion in recent theoretical arguments on this subjects, I arrange and clarify how to develop analysis once the corresponding experimental data become available.     

W boson pair production by electrons and positrons of same helicity

TheW boson pair production by electron and positron of same helicity is computed. The restrictions due to the tree unitarity are exhibited in three sum rules and we have shown how the gauge theories satisfy the sum rules. A simple way to isolate heavy lepton contributions is presented.     

Transverse momentum correlations in hadronic Z decays

Using data obtained with the ALEPH detector at the Z resonance, a measure based on transverse momentum is shown to exhibit a correlation between the two halves of a hadronic event which cannot be explained by energy-momentum conservation, flavour conservation, the imposition of an event axis or imperfect event reconstruction. Two possible interpretations based on existing Monte Carlo models are examined: a) ARIADNE, with the correlation forming early in the parton shower and with the transition from partons to hadrons playing only a minor part; b) JETSET, with the correlation forming at the fragmentation stage. A correlation technique based on a jet cluster analysis is used to make a comparison of the models with the data. It is concluded that both non-perturbative and perturbative effects make important contributions to the observed correlation.     

Impact of the W boson decay width on photon bremsstrahlung accompanying W pair production

The bremsstrahlung spectrum of photons accompanying W pair production depends on the decay width of the unstable W bosons. The dependence arises from the interference between emission at different stages of the production and decay process. We present a quantitative discussion of this effect, and consider the implications for measurements at LEP2 and LC energies. Received: 19 July 2000 / Published online: 13 November 2000     

Vector boson pair production at supercolliders

A fit is made to the data for the proton structure function up toQ ²=10 GeV², including the real γp total cross-section. It is economical and simple, and its form is motivated by physical principles. It is extrapolated down to very small values ofx. Data for the ratio νW ₂ ⁿ /νW ₂ ^p are also fitted.     

The transverse momentum distribution of Drell-Yan pairs in perturbation theory

We calculate, in lowest-order perturbation theory, the cumulative transverse momentum cross section for the Drell-Yan process in the regime m²?p_T²?q², keeping both single and double logarithmic terms. We verify that this distribution takes the proposed form of a product of structure functions evaluated at p_T² and the square of the Sudakov form factor S(p_T²/q²), evaluated to subleading order.     

Transverse momentum distribution of partons in QCD

The renormalization group approach is applied to the study of transverse momentum distribution of partons in QCD. We generalize the method of Altarelli and Parisi to obtain a formula for the mean squared average transverse momentum as a function of Q² and x, the virtual photon mass squared and the longitudinal momentum fraction of the parton. For large Q², it decreases with x in addition to the expected increase with Q². This x-dependence reduces substantially the transverse momentum of massive μ-pairs produced by hadronic collisions from its linear dependence on $\text{(}\text{Q}{}^2\text{ln}\text{Q}{}^2\text{)}\text{1}\text{2}$.