Top mesons

The possibility of formation for a bound state of a quark and a lighter one is investigated using potential model predictions and heavy quark effective theory approach. Resulting estimates for the 1S–2S splitting of the energy levels are compared to the total top decay width . As for the case of toponium, our conclusions show that the probability of formation for T–mesons is negligibly small due to the high top mass value. Received: 2 April 1997     

Discriminating scalar and pseudoscalar weak bosons via toponium → γ + boson

The production of Higg's or neutral technipion spin-zero bosons (szb) in toponium decay is examined. Different methods for determining the parity of these bosons are discussed. The decay width Γ(m³S₁ → γ + szb) is very sensitive to the parity of the szb and it is shown how comparing the widths of different toponium states can be used to determine the szb parity. The method is applicable for a szb within 30% of the toponium mass.     

Threshold behaviour of top production in e+e− annihilation

Implications of electroweak interactions on the threshold behaviour of top production are analyzed. Weak decays of densely spaced high radial excitations of toponium lead to a form of the cross section below threshold that is difficult to distinguish from continuum production. We study the contribution of the vector and axial-vector current to the continuum and calculate the rate for Z decays into top particles as a function of the top quark mass, including QCD corrections.     

Weak decays of heavy vector mesons toponium and open top

We point out that for sufficiently heavy top quark masses, i.e.,m _t ?20 GeV, weak interactions govern the decays ofboth the corresponding pseudoscalar and vector mesons,T andT ^* . Furthermore they significantly modify toponium decays. We discuss in detail the implications forT _b ^* decays and describe how especially its leptonic decays provide such spectacular signatures that they could serve to detect top production in hadron-hadron collisions. We also draw a scenario for toponium decays.     

Large width gluonic bound state in J/Ψ radiative decay

The photon spectrum in the radiative decay of J/Ψ is analysed with a Breit-Wigner and background terms based on a duality hypothesis. We obtain a fit with a resonance, which is considered to be a 2⁺ gluonic bound state, of a mass around 2 GeV and a width around 0.6 GeV. Implications of the ? and toponium decays are also discussed.     

Toponium production in e+e− collisions

We study the properties of toponium states and their production in e⁺e^? collisions with special emphasis on the mass region accessible to SLC and LEP. A formalism for toponium -Z mixing is developed that is applicable for arbitrary mass differences between Z and the toponium state. It is shown that simple lowest-order perturbation theory is equivalent to the mixing formalism up to an accuracy better than one percent in the entire energy range we investigate. The results are illustrated by calculations performed in the framework of two QCD-inspired potential models which predict about 10 narrow states in the mass range around the Z. The mixing effects on the properties of Z are small even in the case of degenerate Z and toponium masses. The effect of electroweak interferences on and around toponium are studied, and analytic forms for cross sections and asymmetries before and after energy smearing are presented. We show that high radial excitations of toponium states below threshold may be difficult to disentangle from the continuum states. A brief survey of the properties of heavy bottom-type quarkonia concludes the paper.     

Minimal and two-doublet Higgs production in heavy quarkonium decays

The decay of a heavy vector toponium state into a photon or Z boson and a Higgs particle is investigated in both the minimal standard model and in a two Higgs doublet model. The decay into a minimal model Higgs boson and a Z is found to be suppressed due to a cancellation of different contributions. However, in the two-doublet case the rates are shown to sometimes be enhanced making this mode an interesting complement to the Wilczek process of the vector particle decaying into a photon and a Higgs boson. It is argued that the combined measurement of these processes would give valuable information on the structure of the Higgs sector of the electroweak interactions. In particular, two-doublet models with restrictions given by supersymmetry are shown to imply a specific pattern for these decays. If there would be a fourth generation, the quarkonium system built from the new b-like quark could decay quite frequently to a Higgs and a Z boson.     

Compositness effects in toponium physics

We study the effects of composite quarks and leptons in toponium physics. Introducing two kinds of non-standard four fermion effective couplings involving top quarks, we compute their influence on \(\theta (t\bar t)\) widths, on cross-sections and asymmetries for \(e^ + e^ - \to \theta \to l\bar l\) , \(q\bar q\) and single quark decay modes. New bounds on four quark contact terms can be inferred at the energies of LEP I and SLC.     

Supersymmetric signature in quarkonium decays

We calculate the heavy quarkonium decay widths for decays to scalar fermion-scalar antifermion pairs. In the light of the supersymmetric interpretation of the recently observed monojets, these decays could be observable in the forthcoming e⁺−e⁻ colliding beam machines. The scalar lepton-scalar antilepton pairs produced by toponium decays is comparable to those produced by direct photon exchanges. The decays of the scalar pair into an electron-positron (or muon-antimuon) pair (carrying about one-half of the total beam energy) together with the missing photinos will be a clean signature of supersymmetry.     

Soft pion emission in pp resonance formation

We calculate hadronic toponium production by specific diagrams obeying colour conservation and charge conjugation. The resulting rates, though lower than those calculated using semi-local duality arguments are encouraging and may allow for toponium discovery at hadronic colliders currently in development.     

THE MIXEFIFNECTG OF Z0 AND TOPONIUN

It is shown that the mixing effect between the Z⁰ and the toponium will significantly affect various properties of toponium state.     

ANALYSIS OF HADRONIC EVENTS

In this paper I summarize some results obtained from analyses of hadronic final state events. The analyzed data sample comes from Mark-J collaboration and covers an energy range from √S=12GeV to √S =46.78GeV. The integrated luminosity is 128.06Pb^－1. We can search for production of open top quarks and toponium by measuring the total hadronic crossection R =3.85±0.02±0.12 was measured in the above mentioned energy range. It is consistent with R≈3.9 as expected from QCD for five different quark flavors. We search for the narrow bound states of the toponium from 39.79GeV to 46.78GeV. The most prominent resonance signal is at a c.m. energy √S=45.12±0.04GeV and results in an upper limit of B_h.Γ_ee≤3.00keV(95% C.L.).     

ϒ production at large transverse momentum as a probe of axigluons

Large-p_T production of J/Ψ and ϒ particles is suggested as a sensitive probe of axigluons of mass less than 40 GeV at the CERN collider and 80 GeV at the Tevatron. It is shown that existing CERN collider data on large-p_T ϒ production exclude axigluon masses less than around 20 GeV. At the projected SSC, ϒ and vector toponium production at large p_T through axigluon exchange by far outweighs the QCD contribution over a vast range of axigluon and toponium masses.     

Rigorous QCD-potential for thet\bar t-system at threshold

Recent evidence for the top mass in the region of 160 GeV for the first time provides an opportunity to use the full power of relativistic quantum field theoretical methods, available also for weakly bound systems. Because of the large decay width Γ of the top quark individual energy-levels in “toponium” will be unobservable. However, the potential for the $t\bar t$ system, based on a systematic expansion in powers of the strong coupling constant α _s can be rigorously derived from QCD and plays a central role in the threshold region. It is essential that the neglect of nonperturbative (confining) effects is fully justified here for the first time to a large accuracy, also justbecause of the large Γ. The different contributions to that potential are computed from real level corrections near the bound state poles of the $t\bar t$ -system which for Γ≠0 move into the unphysical sheet of the complex energy plane. Thus, in order to obtain the different contributions to that potential we may use the level corrections at that (complex) pole. Within the relevant level shifts we especially emphasize the corrections of orderO(α _s ⁴ m _t ) and numerically comparable ones to that order also from electroweak interactions which may become important as well.     

Toponium decay to bottom quarks: QCD corrections

The first-order radiative QCD corrections to the width of toponium decays to bottom quarks are presented.     

Analysis of the QCD sum rules for the heavy quarkonium

We study phenomenologically the QCD sum rules given by Shifman et al. for the heavy quarkonium. In the charmonium sum rules, we find that the contribution of the physical continuum to the moment ?_n is consistent with that of the effective one. As for the bottonium, the sum rules corrected by the Coulomb-like interaction are saturated very well by the four resonances observed at CESR. It is predicted that the³S₁ ground state of the toponium must exist in the range of \(M_{t\bar t} \) =30–44GeV, if the sum rules for the top quark are assumed.     

How to measure the polarization of top quarks

The production of polarized top quarks will be reflected in the polarization of T¹ mesons and can be observed experimentally through their dominant weak decays. It is shown that energy and transverse momentum distributions of top-meson decay products are effected and eventually enhanced or depleted by a factor between 0.5 and 1.5. Parity-violating effects in the lepton distribution from top decay could be observed.     

QCD corrections,virtual heavy quark effects and electroweak precision measurements

QCD corrections to virtual heavy quark effects on electroweak parameters are calculated, which may effect planned precision measurements at SLC and LEP. The influence of toponium and T_b resonances is incorporated as well as the proper threshold behaviour of the imaginary part of the vacuum polarization function. The shift of the W-boson mass from these corrections and their influence on the polarization assymetry are calculated and compared to the envisaged experimental precision.