10 - H1 - Desy

Chapter 9
Results
In this chapter results are presented for the production of prompt photons in photoproduction
region based on the data taken by the H1 detector with an integrated luminosity
of 430 pb −1 . Differential cross sections are compared to QCD calculations and to MC
predictions introduced previously.
The inclusive prompt photon cross sections are shown and discussed in section 9.1. The
differential cross sections in the exclusive photon + jet phase space follow in section 9.2
with special emphasis on the photon - jet correlations. The influence of higher order
corrections is studied in section 9.3. Section 9.5 presents the comparison to the previously
published results in the accordingly adjusted phase space.
9.1 Inclusive prompt photon production in photoproduction
The measured inclusive prompt photon cross section for the kinematic range specified in
table 1.4 is
σ(ep → eγX) = 66.9 ± 1.8 (stat) ± 8.7 (syst) pb.
Both calculations, corrected for all the effects discussed in section 8.7 predict lower cross
sections of 52.1 +5.3
−3.4 pb (FGH) and 56.7+2.3 −3.1 pb (LZ), while the MC expectation from
PYTHIA is 46.4 pb.
Theoretical uncertainties due to missing higher orders are estimated by simultaneously
varying µ R and µ F by a factor of 0.5 to 2.0. In addition, the errors on the theoretical
predictions include all the uncertainties determined in the section 8.7. All error sources
are added in quadrature.
Bin averaged differential cross sections dσ/dE γ T and dσ/dηγ for the inclusive prompt
photon production are given in tables C-1a and C-2a in appendix C and are presented
in the figure 9.1 compared to the prediction from the calculations. Both calculations
are below the data, most significantly at low E γ T
. The LZ calculation gives a reasonable