10 - H1 - Desy

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136 Results 9.3 NLO corrections The leading order Feymann diagrams for direct and resolved prompt photon production is of order (α 2 α 0 s ). The FGH calculation (see 2.2.1) is performed to the order (α2 α s ), which includes already the next-to-leading order correction. The correction increases the calculation by roughly 25% in the inclusive prompt photon phase space and by 10% in the exclusive photon + jet phase space. More differential information is presented in figure 9.6 where few chosen measurements are presented together with the LO calculation, the NLO calculation and the calculation without the box diagram (see 1.13a) considered. The cross section in the inclusive phase space (figures 9.6a and 9.6b) are affected by the correction most significantly at low transverse energies (correction of 32%) and for photons in the forward direction (43%). For the cross sections in the exclusive phase space a very strong positive correction (up to 70%) can be seen for events with the hadronic jet going into the forward direction (figure 9.6d). At the same time, NLO slightly decreases cross sections in the low η jet range. The NLO influence is strongest for the cross sections in bins of x LO γ (figure 9.6e), where additional gluon radiations shift direct events towards values. The correction significantly decreases the cross section in the highest bin (by 40%) but increases it in the other bins. lower x LO γ x LO γ The box diagram increases calculated cross sections on average by 11%. Its influence is the strongest for low pseudorapidities of the photon, where it increases the cross sections by almost 20%. Low values of x LO p are also strongly affected (difference of 20%). An interesting feature can be observed for the cross section in bins of x LO γ variable. Even though the box diagram can not be unambiguously assigned to the direct event class, it contributes only at x LO γ ≈ 1. Since in the final state there are only two particles leaving the hard interaction, the x LO γ definition is properly balanced in the same way as it is the case for leading order direct events. Figure 9.7 presents the same comparison for the cross sections in bins of photon - jet correlation variables in the direct and resolved enhanced phase space separately. In leading order, only back-to-back configuration exists. The photoproduction criteria Q 2 < 1 GeV 2 together with small intrinsic 〈k T 〉 of partons in the proton do not yield any sizeable momentum imbalance which could be seen outside of the lowest p ⊥ bin of 2 GeV width. The next order correction smears out both distributions. The box diagram contributes mainly in the back-to-back configuration in the direct enhanced phase space.
9.3 NLO corrections 137 [pb/GeV] γ dσ / dE T 40 30 20 10 40 a. Inclusive b. LO+NLO 30 LO No box 20 [pb] γ dσ / dη 10 Inclusive [pb] 30 6 8 10 12 14 [GeV] γ E T 30 c. Photon + jet d. [pb] -1 0 1 2 γ η Photon + jet γ dσ / dη 20 jet dσ / dη 20 10 10 [pb] LO γ dσ / dx 150 100 -1 0 1 2 γ η 2000 Photon + jet e. f. [pb] LO p dσ / dx 1500 1000 -1 0 1 2 jet η Photon + jet 50 500 0 0.5 1 xγ LO 0.02 0.04 0.06 xp LO Figure 9.6: The measured cross sections in bins of E γ T (a) and ηγ (b) in the inclusive phase space as well as η γ (c), η jet (d), x LO γ (e) and x LO p (f) in the exclusive phase space plotted together with the FGH calculation (LO+NLO - solid red line). The calculation taking into account only leading order diagrams (LO) is plotted as dotted gray histogram and the one taking into account all except the box diagram is plotted as dashed blue histogram.
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PROMPT PHOTON PRODUCTION IN PHOTOPR
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Abstract This thesis presents measu
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x Contents 4 Event reconstruction a
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xii Contents
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xiv Contents the two photon decay c
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xvi Contents
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2 Theoretical framework Gene- Quark
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4 Theoretical framework charged W
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6 Theoretical framework Neutral and
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8 Theoretical framework α s 0.20 H
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10 Theoretical framework 1.2.4.1 DG
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12 Theoretical framework for the em
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14 Theoretical framework F 2 ⋅ 2
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- - 2) 9O9O9 4 - 70 6- - 7 - Q-
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18 Theoretical framework e e e a) b
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20 Theoretical framework than in th
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22 Theoretical framework ZEUS dσ/E
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24 Theoretical framework claim thou
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26 Theoretical framework Figure 1.2
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28 Theoretical framework Inclusive
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30 Theoretical predictions partons
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32 Theoretical predictions 2.1.2 MC
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34 Theoretical predictions rejectio
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MC set Generator Comments Simulatio
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38 Theoretical predictions contribu
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40 The H1 experiment at HERA Hall N
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42 The H1 experiment at HERA y θ z
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44 The H1 experiment at HERA resolu
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46 The H1 experiment at HERA the el
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48 The H1 experiment at HERA under
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50 The H1 experiment at HERA not be
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52 Event reconstruction and presele
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64 Prompt photon selection the rema
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66 Prompt photon selection ∆η <
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68 Prompt photon selection reconstr
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70 Prompt photon selection Events 5
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72 Prompt photon selection Selectio
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74 Photon signal extraction γ π0
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76 Photon signal extraction Events
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78 Photon signal extraction CB1 CB2
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80 Photon signal extraction Figure
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82 Photon signal extraction n∏ va
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84 Photon signal extraction 〈S〉
Page 102 and 103: 86 Calibration and tuning • Backg
Page 104 and 105: 88 Calibration and tuning χ 2 /NDF
Page 106 and 107: 90 Calibration and tuning energy on
Page 108 and 109: 92 Calibration and tuning D Ej 1.1
Page 110 and 111: 94 Calibration and tuning
Page 112 and 113: 96 Cross section building The corre
Page 114 and 115: 98 Cross section building • L-cur
Page 116 and 117: 100 Cross section building (Reconst
Page 118 and 119: 102 Cross section building 8.2.1.1
Page 120 and 121: 104 Cross section building Figure 8
Page 122 and 123: 106 Cross section building section
Page 124 and 125: 108 Cross section building the Pull
Page 126 and 127: 110 Cross section building contribu
Page 128 and 129: 112 Cross section building 8.3.2 Sy
Page 130 and 131: 114 Cross section building 8.4 Cros
Page 132 and 133: 116 Cross section building 8.4.3 Cr
Page 134 and 135: 118 Cross section building The doub
Page 136 and 137: 120 Cross section building 8.6.2 To
Page 138 and 139: 122 Cross section building one outp
Page 140 and 141: 124 Cross section building MPI f th
Page 142 and 143: f f f f f f f f f f f f 126 Cross s
Page 144 and 145: 128 Cross section building PDF unce
Page 146 and 147: 130 Results description of the shap
Page 148 and 149: 132 Results 9.2 Prompt photon + jet
Page 150 and 151: 134 Results [pb] LO dσ / dx γ 100
Page 154 and 155: 138 Results [pb/GeV] dσ / dp 15 10
Page 156 and 157: 140 Results transverse momentum imb
Page 158 and 159: 142 Results [pb/GeV] γ dσ / E T 2
Page 160 and 161: 144 Conclusions and outlook is cons
Page 163 and 164: A Analysis Binning 147 A Analysis B
Page 165 and 166: A Analysis Binning 149 Bin E γ T,O
Page 167 and 168: B Alternative classifier definition
Page 169 and 170: C Cross Section Tables 153 C Cross
Page 171 and 172: C Cross Section Tables 155 η γ E
Page 173 and 174: C Cross Section Tables 157 η γ d
Page 175 and 176: C Cross Section Tables 159 η jet d
Page 177 and 178: C Cross Section Tables 161 x LO γ
Page 179 and 180: C Cross Section Tables 163 x LO γ
Page 181 and 182: List of Figures 1.1 Lowest order Fe
Page 183 and 184: List of Figures 167 6.2 Shower shap
Page 185 and 186: List of Tables 169 List of Tables 1
Page 187 and 188: List of Tables 171 C-8b Corrections
Page 189 and 190: References [1] C. Amsler et al.,
Page 191 and 192: References 175 [32] R. Nisius, “T
Page 193 and 194: References 177 [63] P. A. Aarnio et
Page 195 and 196: References 179 [97] W. Braunschweig
Page 197 and 198: References 181 [129] J. M. Butterwo
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