10 - H1 - Desy

1.4 Recent prompt photon measurements 23
dσ/dη γ (pb)
6
ZEUS 96-00
PYTHIA 6.206 (x2.3)
HERWIG 6.1 (x7.9)
(pb GeV -1 )
1.5
Events
4
dσ/dE T
γ
1
2
0
-0.5 0 0.5
η γ
0.5
0
ZEUS 96-00
PYTHIA 6.206 (x2.3)
HERWIG 6.1 (x7.9)
a) b) c)
5 6 7 8 9 10
E T γ (GeV)
10
10 2 50 75 100 125 150 175 200 225 250 275
Q 2 (GeV 2 )
Figure 1.18: Inclusive prompt photon differential cross sections dσ/dη γ (a), dσ/dE γ T
(b) and dσ/dQ 2 (c) in DIS as measured by the ZEUS [41] collaboration compared to MC
predictions.
[pb]
dσ/dη
γ
H1
40 H1 Data
LO(α 3 ) LL+QQ+LQ
LO(α 30
3 ) LL
LO(α 3 ) QQ
20
10
2
a) H1 b) 10 H1 Data
H1 c)
[pb/GeV]
dσ/dE
H1 Data
LO(α 3 ) LL+QQ+LQ
LO(α 20
3 ) LL
LO(α 3 ) QQ
10
[pb/GeV
dσ/dQ
2
γ
T
2
]
-1
10
LO(α 3 ) LL+QQ+LQ
LO(α 10
3 ) LL
LO(α 3 ) QQ
1
[pb]
dσ/dη
γ
0
-1 0 1
40 H1 Data
30
20
10
H1
γ
η
SUM
PYTHIA
RAPGAP (rad.)
[pb/GeV]
dσ/dE
γ
T
0
20
10
4 6 8 10
γ
E
[GeV]
T
H1 Data
SUM
PYTHIA
RAPGAP (rad.)
-2
10
10
2
10
2
2
Q [GeV
]
d) H1 e) H1
H1 Data f)
[pb/GeV
dσ/dQ
2
2
]
2
10
10
1
-1
10
SUM
PYTHIA
RAPGAP (rad.)
0
-1 0 1
γ
η
0
4 6 8 10
γ
E
[GeV]
T
10
2
10
2
2
Q [GeV
]
Figure 1.19: Inclusive prompt photon differential cross sections dσ/dη γ (a, d), dσ/dE γ T
(b, e) and dσ/dQ 2 (c, f) in DIS as measured by the H1 [43] collaboration compared to
LO QCD calculation (a-c) and MC prediction (d-f). The direct photon radiation from
the quark is indicated by the dashed black line, radiation from the electron line by a red
solid line and the sum of the predictions by a blue solid line.
energies. Figure 1.20 summarises results from pp and p¯p collisions. Results are given as
the ratio of data to QCD calculations as a function of the reduced variable x T = 2E γ T /√ s.
The data used in the figure is summarised in table 1.3 (for further details and references
see [44]). With an exception of the measurement performed by E706 experiment, the data
agree well with the NLO calculations all over the studied x T range. The agreement can be
still improved by the introduction of ’intrinsic k T ’ for the partons within a proton. This
situation motivated the introduction of an extra parameter 〈k T 〉 to account for the effects
of multiple soft gluon emissions associated to hard partonic scattering [45]. Authors of [46]