10 - H1 - Desy

1.5 Analysis motivation and goals 25
Experiment Accelerator Initial state
√ s year
R806 ISR pp 63 GeV 1982
WA70 SPS pp 23 GeV 1988
UA1 Sp¯pS p¯p 630 GeV 1988
R110 ISR pp 63 GeV 1989
R807 ISR pp 63 GeV 1990
UA2 Sp¯pS p¯p 630 GeV 1991
UA6 SppS p¯p 24.3 GeV 1998
UA6 Sp¯pS p¯p 24.3 GeV 1998
E706 Tevatron fixed target pBe 31.6 GeV 1998
E706 Tevatron fixed target pBe 38.8 GeV 1998
D0 Tevatron collider p¯p 630 GeV 2000
D0 Tevatron collider p¯p 1800 GeV 2001
CDF Tevatron collider p¯p 630 GeV 2001
CDF Tevatron collider p¯p 1800 GeV 2001
Table 1.3: Summary of the experiments whose results are presented in figure 1.20. The
last column indicates the starting year of the given experiment.
that the studied phase space is directly visible by the measurement, a requirement on the
inelasticity y is introduced. The low inelasticity region is experimentally dominated by
beam gas collision events, while high y events resemble the topology of the deep inelastic
scattering. In this analysis, the inelasticity is therefore restricted to 0.1 < y < 0.7 range.
The transverse energy 6 < E γ T < 15 GeV and pseudorapidity −1.0 < ηγ < 2.4 of the
studied photons is chosen such as to correspond to the acceptance of the experiment.
Finally, the measurement is restricted only to photons that are well isolated from the
surrounding hadronic activity. As shown in [39,48] the photon isolation requirement is
able to decrease the influence of the quark-to-photon fragmentation, which is not known
to a very good precision. Furthermore the isolation requirement is needed for the analysis
to suppress background from decay photons. The isolation is ensured with the method
similar to the recent prompt photon measurements [38,43] by the cut on the z variable,
z > 0.9, where
z =
Eγ T
E γ−jet
T
, (1.39)
where E γ−jet
T
is the transverse energy of the jet which the prompt photon is assigned to
(for details of the jet algorithm see section 4.2.2). This isolation definition is both collinear
and infrared safe.
Collecting the information of both the photon and the leading hadronic jet gives more
insight into the underlying dynamics of the prompt photon production process. The most
general measurement can be performed in bins of transverse energy and pseudorapidity
of both the photon (E γ T , ηγ ) and the accompanying hadronic jet (E jet
T
and η jet ). Prompt