July 1, 1993
The expected large mass $m_t$ of the top quark provides for the first time a chance to discuss the bound-states of the corresponding quantum system as the nonabelian generalization of positronium, using the full power of relativistic quantum field theoretic methods which are available for weakly bound systems. Thus our approach differs in principle from the one used in the vast phenomenological literature on quarkonium potentials. We emphasize especially the corrections of energy levels which are of order $\a^4 m_t$ or numerically comparable to that order, and which have no counterpart in the 'relativistic' corrections of QED. In contrast to previous computations we give analytic expressions for all contributions considered in our present work, hopefully preparing the ground for further similar calculations.
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August 2, 1994
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 $\G$ 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 $\a_s$ can be rigorousl...
August 3, 1994
Although individual levels of toponium will be unobservable, the top--anti--top system near threshold fulfills all requirements of a rigorous perturbation theory in QCD for weakly bound systems. Corresponding techniques from positronium may thus be transferred successfully to this case. After clarifying the effect of a non-zero width we calculate the $t\bar{t}$ potential to be used for the calculation of e.g. the cross-sections near threshold.
October 14, 2002
In this talk I review the calculation of the third order corrections to the heavy quarkonium spectrum in the nonrelativistic effective theory framework and its application to the phenomenology of top quark threshold production.
November 27, 2024
In this article, we solve the instantaneous Bethe-Salpeter equation with a linear plus Coulomb potential and conduct a meticulous study of the mass spectrum and wave function of toponium. Our investigation reveals that, owing to the exceedingly heavy mass of the top quark, the mass splitting between singlet and triplet states, as well as within the triplet states, is negligible. Consequently, relativistic corrections can be safely disregarded in the study of toponium. As such...
January 31, 1995
The bound state problem for a fermion-antifermion system is considered taking into account a finite decay width of the constituents. We propose an exactly solvable relativistic zero order equation similar to that of Barbieri and Remiddi, but including a constant width. We focus especially on the $t\bar{t}$ system for which we reconsider our recent calculation of the bound state corrections to the toponium width, which was performed in the narrow width approximation and needed...
September 29, 2000
The top quark-antiquark pair threshold production at future High Energy Photon Colliders is considered in view of the recent advances in the theoretical description of the nonrelativistic heavy quark dynamics.
November 9, 1995
In this talk I will use effective lagrangian and discuss possible new physics associated with top quark.
November 13, 2024
Numerical wave functions (WFs), root mean square (RMS) radii, $E1$ and $M1$ radiative transitions, and branching ratios of $S, P, D$ and $F$ states of toponium mesons ($t\overline{t}$) are calculated using a non-relativistic quark potential model (NRQPM). Shooting method is used to solve the radial Schrodinger equation to find the radial wave functions which are used in the calculation of properties of mesons. Calculated masses are compared with the theoretical available data...
February 19, 1993
Recently it has been suggested that top quarks, or very massive fourth generation quarks, might surround themselves with a Higgs "bag" of deformation of the Higgs expectation value from its vacuum magnitude. In this paper we address the question of whether such nonlinear Higgs-top interaction effects are subject to experimental test. We first note that if top quarks were necessarily accompanied by Higgs "bags", then top quark weak decay would involve the sudden disruption of ...
June 22, 2015
Combining recent perturbative analyses on the static QCD potential and the quark pole mass, we find that, for the heavy quarkonium states $c\bar{c}$, $b\bar{b}$ and $t\bar{t}$, (1) ultra-soft (US) corrections in the binding energies are small, and (2) there is a stronger cancellation of IR contributions than what has been predicted by renormalon dominance hypothesis. By contrast, for a hypothetical heavy quarkonium system with a small number of active quark flavors ($n_l\appr...