Indications for an extra neutral gauge boson in electroweak precision data

A new analysis of the hadronic peak cross section at LEP 1 implies a small amount of missing invisible width in Z decays, while the effective weak charge in atomic parity violation has been determined recently to 0.6% accuracy, indicating a significantly negative S parameter. As a consequence, the data are described well if the presence of an extra Z' boson, such as predicted in grand unified theories, is assumed. Moreover, the data are now rich enough to study an arbitrary extra Z' boson and to determine its couplings in a model independent way. An excellent fit to the data is obtained in this case, suggestive of a family nonuniversal Z' similar to those predicted in a class of superstring theories.     

Searching for an extra neutral gauge boson from muon pair production at LHC

We search for signatures of the extra neutral gauge boson Z^′$Z^{\prime }$, predicted in some extensions of the Standard Model, from the analysis of some distributions for p+p→μ⁺+μ⁻+X$p+p\to {\mu }^{+}+{\mu }^{-}+X$, where the only exotic particle involved is Z^′$Z^{\prime }$. In addition to the invariant mass and charge asymmetry distributions, we propose in our search to use the transverse momentum distribution (pT$p_T$) as an observable. We do our calculation for two values of the LHC center of mass energy (7 and 14 TeV), corresponding to 1 and 100 fb⁻¹ of luminosity, in order to compare our findings from some models with the distributions following from the Standard Model. By applying convenient cuts in the invariant mass, we show that the final particles pT$p_T$ distributions can reveal the presence of an extra neutral gauge boson contribution. We also claim that it is possible to disentangle the models considered here and we emphasize that the minimal version of the model, based on SUC₍₃₎×SUL₍₃₎×UX₍₁₎$\mathit{SU}{(3)}_C\times \mathit{SU}{(3)}_L\times U{(1)}_X$ symmetry, presents the more clear signatures for Z^′$Z^{\prime }$ existence.     

Identification of a horizontal gauge boson in hadronic collisions

We compare distributions of leptons produced in hadronic collisions, by a horizontal neutral gauge boson, suggested by the model, to those produced by other theoretically motivated neutral gauge bosons occurring in left–right symmetric models and in superstring-inspired models. Forward–backward asymmetries in the gauge boson leptonic decay are found to be sensitive to specific forms of the couplings. The asymmetries are expected to be maximal for distinguishing it from the other Z's. Received: 17 September 2001 / Published online: 7 December 2001     

Supersymmetry search via gauge boson fusion

We propose a novel method for the search of supersymmetry, especially for the electroweak gauginos at the large hadron collider (LHC). Gauge boson fusion technique was shown to be useful for heavy and intermediate mass Higgs bosons. In this article, we have shown that this method can also be applied to find the signals of EW gauginos in supersymmetric theories where the canonical search strategies for these particles fail.     

The gauge boson sector ofU(1) lattice theories

We examine theU(1) Hamiltonian lattice gauge theory in (2+1) and (3+1) dimensions. We set up a differential eigenvalue equation for the energy levels of the system, valid for all values of the coupling parameter. We show how the standard strong coupling results are retrieved, and also present a weak coupling solution which exhibits (unconfined) transverse photons as the phonons of the lattice. The lattice approach is thus seen to be appropriate for non-confining as well as for confining systems.     

Higgs boson emission in very rare decays of an extra vector boson

We explore the phenomenological structure of E ₆-inspired grand unified group with the gauge group SU(3)_c×SU(2)_L×U(1)_Y×U(1), the emphasis being laid upon its implications for Higgs boson observation. In particular, we discuss the probability for the mass eigenstate Z ₂ to decay into a Higgs particle and a bound state composed of heavy quarks. Constraints on and relations between the Z ₂ and Higgs masses are presented.     

Littlest Higgs模型中通过e^+e^-对撞研究新规范玻色子B_H与SM中规范玻色子的伴随产生过程

计划中的高能量、高亮度对撞机ILC在寻找新物理模型所预言的新的重粒子方面具有很大的潜力。本文,我们研究了在ILC上,通过过程e^+e^- ->r(Z)B_H发现littlest Higgs模型中最轻的新规范玻色子B_H的可能性。结果显示,在较大的参数空间范围,这两个过程都有较大的产生截面,能产生足够的信号探测B_H,尤其是对过程e^+e^- ->rB_H。另外,B_H的一些衰变道可以产生特征比较明显背景比较干净的信号。如果B_H存在,随着ILC的运行,新的规范玻色子B_H应能通过这两过程观测。     

Gamma rays and positrons from a decaying hidden gauge boson

We study a scenario that a hidden gauge boson constitutes the dominant component of dark matter and decays into the standard model particles through a gauge kinetic mixing. Interestingly, gamma rays and positrons produced from the decay of hidden gauge boson can explain both the EGRET excess of diffuse gamma rays and the HEAT anomaly in the positron fraction. The spectra of the gamma rays and the positrons have distinctive features; the absence of line emission of the gamma ray and a sharp peak in the positron fraction. Such features may be observed by the FGST and PAMELA satellites.     

Bounds on warped extra dimensions from a Standard Model-like Higgs boson

We point out that the discovery of a light Higgs boson in the γγ, ZZ, and WW   decay channels at the LHC, with cross sections not far from the predictions of the Standard Model, would have profound implications for the parameters of warped extra-dimension models with a brane-localized Higgs sector. Due to loop effects of Kaluza–Klein particles, these models predict a significant reduction of the Higgs production cross section via gluon–gluon fusion, combined with an enhancement of the ratio Br(h→γγ)/Br(h→ZZ)$\mathrm{Br}(h\to \gamma \gamma )/\mathrm{Br}(h\to ZZ)$ in large parts of parameter space. LHC measurements of these decays will probe Kaluza–Klein masses up to the 10 TeV range, exceeding by far the reach for direct production.     

Production of a decoupled neutral gauge boson at the SSC

We consider an extension of the standard model with an extra neutral gauge bosonV which does not couple to the usual fermions or mix with the standardZ boson. A new fermion, which is either a color-triplet (Q) or a color-singlet (L), and a singlet Higgs scalar (X) are generic particles required for the extension group.V can be produced copiously by the process . We find 0760 0712 V 3 that there will be at least a few hundredV's produced at the SSC per year if the masses ofV andQ are less than 1 and 0.3 TeV respectively. Although the mixing of the standard and new Higgs scalars is small, the decay of the standard model Higgs scalar,H ₁2V, is comparable to the corresponding standard processes,H ₁2Z. A heavy standard model Higgs may open an important channel for the study of a new neutral gauge boson.     

A boson representation for SU (N) lattice gauge theories

SU(N) lattice gauge theories are reformulated in terms of fields varying over non-compact spaces ^N , transforming asN dimensional representations of SU(N) and integrated with Gaussian measure. This reformulation is equivalent to a boson operator representation. Strong coupling expansions based on this formalism do not involve SU(N) vector coupling coefficients.     

具有T宇称的最小Higgs模型与LHC上Higgs波色子与弱规范波色子的联合产生

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.     

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.     

Associated productions of the new gauge boson BH in the Littlest Higgs model with a SM gauge boson via e+e- collision

With the high energy and luminosity, the planned ILC has the considerable capability to probe the new heavy particles predicted by the new physics models. In this paper, we study the potential to discover the lightest new gauge boson BH of the Littlest Higgs model via the processes e+e- →γ(Z)BH at the ILC. The results show that the production rates of these two processes are large enough to detect BH in a wide range of the parameter spaces, specially for the process e+e- →γBH. Furthermore, there exist some decay modes for BH which can provide the typical signal and clean backgrounds. Therefore, the new gauge boson BH should be observable via these production processes with the running of the ILC if it exist.     

Associate production of a heavy quark and a gauge boson atep colliders

We study the reactione+p→e+Q+V+X, whereQ stands for ac orb quark andV=γ,W orZ. At HERA only the combinationQ=c,V=γ seems promising; it should allow to measure thec-quark density inside both the proton and the photon. Here,c-quarks are identified through their mounic decays. At LEP×LHC, \(\gamma + b(\bar b)\) and \(W^ \pm + c(\bar c)\) production also have sizeable rates; the first reaction might allow to measure theb content of the photon, while the second reaction can determine the strange-sea and the valenced-quark distributions in the proton, and might provide a statistically independent measurement of theWWγ vertex.     

Phenomenology of a second neutral gauge boson in the Drell-Yan process

We discuss the influence of a second neutral gauge boson to the Drell-Yan process. We find that for energies available in the near future and even at present energies, there are sizeable differences in the predictions of different models for the forward-backward asymmetry and the longitudinal polarization of the lepton.