Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Tests of the Standard Model and Constraints on New Physics from
  Measurements of Fermion-pair Production at 189 GeV at LEP   Cross-sections and angular distributions for hadronic and lepton pair final
states in e+e- collisions at a centre-of-mass energy near 189 GeV, measured
with the OPAL detector at LEP, are presented and compared with the predictions
of the Standard Model. The results are used to measure the energy dependence of
the electromagnetic coupling constant alpha_em, and to place limits on new
physics as described by four-fermion contact interactions or by the exchange of
a new heavy particle such as a sneutrino in supersymmetric theories with
R-parity violation. A search for the indirect effects of the gravitational
interaction in extra dimensions on the mu+mu- and tau+tau- final states is also
presented.

15
The categories of this paper are: nucl-ex
26
The categories of this paper are: bayes-an
2
The categories of this paper are: math
5
The categories of this paper are: gr-qc
28
The categories of this paper are: alg-geom
12
The categories of this paper are: nucl-th
6
The categories of this paper are: astro-ph
35
The categories of this paper are: mtrl-th
31
The categories of this paper are: ao-sci
36
The categories of this paper are: cmp-lg
1
The categories of this paper are: cs
16
The categories of this paper are: stat
9
The categories of this paper are: nlin
14
The categories of this paper are: math-ph
11
The categories of this paper are: hep-lat
20
The categories of this paper are: acc-phys