Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Two-photon dilepton production in proton-proton collisions: two
  alternative approaches   We investigate different methods to incorporate the effect of photons in hard
processes. We compare two different approaches used for calculating cross
sections for two-photon $p p \to l^+ l^- X$ process. In one of the approaches
photon is treated as a collinear parton in the proton. In the second approach
recently proposed a $k_T$-factorization method is used. We discuss how results
of the collinear parton model depend on the initial condition for the QCD
evolution and discuss an approximate treatment where photon is excluded from
the combined QCD-QED evolution. We demonstrate that it is not necessary to put
photon into the evolution equation as often done recently but it is sufficient
to use a simplified approach in which photon couples to quarks and antiquarks
which by themselves undergo DGLAP evolution equations. We discuss sensitivity
of the results to the choice of structure function parametrization and
experimental cuts in the $k_T$-factorization approach. A new optimal structure
function parametrization is proposed. We compare results of our calculations
with recent experimental data for dilepton production and find that in most
cases the contribution of the photon-photon mechanism is rather small. We
discuss how to enhance the photon-photon contribution. We also compare our
results to those of recent measurements of exclusive and semi-exclusive $e^+
e^-$ pair production with certain experimental data by the CMS collaboration.

20
The categories of this paper are: acc-phys
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
27
The categories of this paper are: comp-gas
8
The categories of this paper are: hep-ex
31
The categories of this paper are: ao-sci
17
The categories of this paper are: q-fin
3
The categories of this paper are: physics
18
The categories of this paper are: econ
25
The categories of this paper are: patt-sol
13
The categories of this paper are: quant-ph
32
The categories of this paper are: atom-ph
12
The categories of this paper are: nucl-th
34
The categories of this paper are: chem-ph