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 High Energy Physics - Phenomenology , 2013, Abstract: The weak bosons are bound states of two fermions and their antiparticles, denoted as haplons. The confinement scale of the associated gauge group SU(2) is of the order of 0.5 TeV. Besides the weak bosons there exist also new bosons, an SU(2)-triplet and a singlet, with a mass of the order of 0.5 TeV. The neutral singlet boson and its antiparticle are stable and provide the dark matter in the universe.
 Physics , 2010, Abstract: We study phenomenological consequences of the Standard Model extension by the new spin-1 chiral fields with the internal quantum numbers of the electroweak Higgs doublets. There are at least three different classes of theories, all motivated by the hierarchy problem, which predict new vector weak-doublets with masses not far from the electro-weak scale. We discuss resonance production of these neutral chiral Z* bosons at hadron colliders. The bosons can be observed as a Breit-Wigner resonance peak in the invariant dilepton mass distributions in the same way as the well-known extra gauge Z' bosons. This includes them into a list of very interesting objects for early searches with the first LHC data. Moreover, the Z* bosons have unique signatures in transverse momentum, angular and pseudorapidity distributions of the final leptons, which allow to distinguish them from the other heavy neutral resonances.
 Physics , 2002, DOI: 10.1103/PhysRevD.68.035012 Abstract: We study theoretical and experimental constraints on electroweak theories including a new color-singlet and electrically-neutral gauge boson. We first note that the electric charges of the observed fermions imply that any such Z' boson may be described by a gauge theory in which the Abelian gauge groups are the usual hypercharge along with another U(1) component in a kinetic-diagonal basis. Assuming that the observed quarks and leptons have generation-independent U(1) charges, and that no new fermions couple to the standard model gauge bosons, we find that their U(1) charges form a two-parameter family consistent with anomaly cancellation and viable fermion masses, provided there are at least three right-handed neutrinos. We then derive bounds on the Z' mass and couplings imposed by direct production and Z-pole measurements. For generic charge assignments and a gauge coupling of electromagnetic strength, the strongest lower bound on the Z' mass comes from Z-pole measurements, and is of order 1 TeV. If the new U(1) charges are proportional to B-L, however, there is no tree-level mixing between the Z and Z', and the best bounds come from the absence of direct production at LEPII and the Tevatron. If the U(1) gauge coupling is one or two orders of magnitude below the electromagnetic one, these bounds are satisfied for most values of the Z' mass.
 A. Safonov Physics , 2010, DOI: 10.3360/dis.2009.62 Abstract: This contribution reports on some of the most recent searches for new heavy neutral bosons and leptoquarks performed at the Tevatron experiments.
 A. Leike Physics , 1998, DOI: 10.1016/S0370-1573(98)00133-1 Abstract: The phenomenological constraints on extra neutral gauge bosons at present and at future colliders are reviewed. Special attention is paid to the influence of radiative corrections, systematic errors, and kinematic cuts on the Z' constraints. Simple estimates of the Z' constraints from different reactions are derived. They make the physical origin of these constraints transparent. The results existing in the literature are summarized and compared with the estimates. The consequence of model assumptions on the Z' constraints is discussed. The paper starts with an overview of Z' parameters and the possible links between them by model assumptions. It continues with a discussion of Z' limits and Z' measurements in different reactions at e+e- and mu+mu- colliders. It follows an overview of the corresponding limits at proton colliders. Possible Z' constraints from other reactions as ep collisions, atomic parity violation, neutrino scattering and cosmology are briefly mentioned.
 Physics , 1996, Abstract: This is a short review of present and future limits on new neutral gauge bosons, in particular on hadrophilic or leptophobic $Z'$s recently proposed to interpret the observed fluctuations of $\Gamma _{c,b}$ at LEP. Light gauge bosons coupled to lepton number differences or to baryon number are also examples of the model dependence of these bounds. The mixing between the $U(1)$ factors plays an important role in the phenomenology of these extended electroweak models. Future improvements based on the analysis of precise electroweak data are emphasized.
 Physics , 2006, DOI: 10.1140/epjc/s2006-02569-7 Abstract: The four LEP collaborations, ALEPH, DELPHI, L3 and OPAL, have searched for the neutral Higgs bosons which are predicted by the Minimal Supersymmetric Standard Model (MSSM). The data of the four collaborations are statistically combined and examined for their consistency with the background hypothesis and with a possible Higgs boson signal. The combined LEP data show no significant excess of events which would indicate the production of Higgs bosons. The search results are used to set upper bounds on the cross-sections of various Higgs-like event topologies. The results are interpreted within the MSSM in a number of "benchmark" models, including CP-conserving and CP-violating scenarios. These interpretations lead in all cases to large exclusions in the MSSM parameter space. Absolute limits are set on the parameter tanb and, in some scenarios, on the masses of neutral Higgs bosons.
 Physics , 2004, DOI: 10.1140/epjc/s2004-02011-4 Abstract: Searches for neutral Higgs bosons produced at LEP in association with Z bosons, in pairs and in the Yukawa process are presented in this paper. Higgs boson decays into b quarks, tau leptons, or other Higgs bosons are considered, giving rise to four-b, four-b+jets, six-b and four-tau final states, as well as mixed modes with b quarks and tau leptons. The whole mass domain kinematically accessible at LEP in these topologies is searched. The analysed data set covers both the LEP1 and LEP2 energy ranges and exploits most of the luminosity recorded by the DELPHI experiment. No convincing evidence for a signal is found, and results are presented in the form of mass-dependent upper bounds on coupling factors (in units of model-independent reference cross-sections) for all processes, allowing interpretation of the data in a large class of models.
 Physics , 1995, DOI: 10.1103/PhysRevD.53.1537 Abstract: With $\mu\to e\gamma$ decay forbidden by multiplicative lepton number conservation, we study muonium--antimuonium transitions induced by neutral scalar bosons. Pseudoscalars do not induce conversion for triplet muonium, while for singlet muonium, pseudoscalar and scalar contributions add constructively. This is in contrast to the usual case of doubly charged scalar exchange, where the conversion rate is the same for both singlet and triplet muonium. Complementary to muonium conversion studies, high energy $\mu^+e^- \to \mu^- e^+$ and $e^-e^- \to \mu^- \mu^-$ collisions could reveal spectacular resonance peaks for the cases of neutral and doubly charged scalars, respectively.
 Physics , 1997, DOI: 10.1119/1.18669 Abstract: We review how antiparticles may be introduced in classical relativistic mechanics, and emphasize that many of their paradoxical properties can be more transparently understood in the classical than in the quantum domain.
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