Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: QCD corrections to t\bar t b \bar b productions via photon-photon
  collisions at linear colliders   We calculated the complete next-to-leading order(NLO) QCD corrections to the
$t\bar t b \bar b$ production process at a $\gamma \gamma$ collider in the
standard model(SM). The calculation of the one-loop QCD correction includes the
evaluations of the hexagon and pentagon amplitudes. We studied the NLO QCD
corrected total cross section, the distributions of transverse momenta of final
top- and bottom-quark states, and the dependence of the cross section on
renormalization scale $\mu$. It shows that NLO QCD correction generally
increases the LO cross section in our chosen parameter space, and the K-factor
varies from 1.70 to 1.14 when colliding energy goes up from $400 GeV$ to $2
TeV$. We find that the correction distinctly changes the distributions of
transverse momenta of the final top- and bottom-quark states, and the NLO QCD
correction obviously improves the independence of the cross section for process
$\gamma\gamma \to t\bar t b\bar b$ on the renormalization scale.

8
The categories of this paper are: hep-ex
4
The categories of this paper are: cond-mat
27
The categories of this paper are: comp-gas
10
The categories of this paper are: q-bio
17
The categories of this paper are: q-fin
18
The categories of this paper are: econ
11
The categories of this paper are: hep-lat
21
The categories of this paper are: adap-org
37
The categories of this paper are: supr-con
32
The categories of this paper are: atom-ph
19
The categories of this paper are: eess
23
The categories of this paper are: solv-int
31
The categories of this paper are: ao-sci
3
The categories of this paper are: physics
1
The categories of this paper are: cs
34
The categories of this paper are: chem-ph