10 - H1 - Desy

24 Theoretical framework
claim though that there is no need for additional k T to force the agreement between QCD
predictions and experiment, with the sole exception of E706 results, which they claim are
inconsistent with other experiments. So the k T hypothesis remains controversial [47].
Figure 1.21 shows the comparison of data cross sections to the NLO calculations in bins
of E γ T
. The different slope of data and theory for E706 experiment is clearly visible.
Figure 1.20: Ratio data to theory prompt photon cross section for collider and fixed
target hadronic collisions. Figure taken from [44].
1.5 Analysis motivation and goals
Prompt photon results are presented in the form of cross sections with the binning and
phase space chosen such as to enhance sensitivity to the studied effects. All the cross sections
calculated in this analysis are identified below and shortly discussed. Furthermore,
in this section the phase space of the measurement is defined and referred throughout the
following chapters.
The production of prompt photons with high transverse momentum can be calculated in
perturbation theory, and one may study the prompt photon cross sections in order to test
the quality and relevance of the QCD calculations. The measurement of inclusive prompt
photon production is performed in bins of its transverse energy E γ T
and pseudorapidity
η γ . Those measurements are performed in the phase space with the event kinematics
conditions and the photon condition later on referred to as the inclusive prompt photon
phase space. The measurement is restricted to the photoproduction region by the cut
on the negative four momentum transfer squared Q 2 < 1 GeV 2 . In addition, to ensure