10 - H1 - Desy

130 Results
description of the shape of η γ , whereas the FGH calculation is significantly below the data
for central and backward photons (η γ < 0.9).
The double differential measurement dσ 2 /dE γ T dηγ is given in table C-3a and is presented in
figure 9.2. In this case, results are also compared to the PYTHIA Monte Carlo prediction.
LZ provides a reasonable description of the data with the exception of the lowest E γ T bin
in the central η γ (0.2 < η γ < 0.9) region. The FGH calculation underestimates the cross
section in the central (0.2 < η γ < 0.9) and backward (η γ < −0.6) region. Here, it is
significantly below the data. The prediction from PYTHIA underestimates the measured
cross section by roughly 45%, most significantly at low E γ T .
[pb/GeV]
dσ / dE T
γ
30
20
10
H1
Inclusive Prompt Photon Cross Sections
30
a. H1
b.
H1 Data
FGH (NLO)
LZ (k fact)
T
[pb]
γ
dσ / dη
20
10
R
0
6 8 10 12 14
1
corr. error
0.5
6 8 10 12 14
γ
[GeV]
E T
R
0
-1 0 1 2
1
0.5
-1 0 1 2
γ
η
Figure 9.1: The differential inclusive prompt photon cross sections in bins of E γ T
(a) and
η γ (b). The inner error bars indicate the fully uncorrelated error, while the full error bars
contain in addition the correlated error added in quadrature. The measurement is plotted
together with the NLO collinear calculation prediction (FGH) and the prediction based
on the k T factorisation approach (LZ). The lower part of the plot presents the ratio R of
the FGH prediction to the measurement together with the data points. The error bars
associated with the points indicate the fully uncorrelated error, while the yellow band
shows the fully correlated error.