Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Relativistic Bound State Equation for Unstable Fermions and the Toponium
  Width   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 the use of second order Bethe-Salpeter perturbation
theory. We show that one obtains the same result already in first order BS
perturbation theory if one uses our present approach. Furthermore the large
cancellations of gauge dependent terms is demonstrated to be a consequence of a
Ward identity. This cancellation mechanism is shown to be valid for general
fermion-antifermion systems.

29
The categories of this paper are: funct-an
31
The categories of this paper are: ao-sci
33
The categories of this paper are: plasm-ph
34
The categories of this paper are: chem-ph
2
The categories of this paper are: math
18
The categories of this paper are: econ
20
The categories of this paper are: acc-phys
25
The categories of this paper are: patt-sol
4
The categories of this paper are: cond-mat
35
The categories of this paper are: mtrl-th
5
The categories of this paper are: gr-qc
16
The categories of this paper are: stat
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The categories of this paper are: alg-geom
9
The categories of this paper are: nlin
19
The categories of this paper are: eess
8
The categories of this paper are: hep-ex