Rivet analyses referenceATLAS_2012_I1084540Rapidity gap cross sections measured with the ATLAS detector in $pp$ collisions at $\sqrt{s} = 7$ TeV.Experiment: ATLAS (LHC 7TeV) Inspire ID: 1084540 Status: VALIDATED Authors:
Beam energies: (3500.0, 3500.0) GeV Run details:
Pseudorapidity gap distributions in proton-proton collisions at $\sqrt{s} = 7$ TeV are studied using a minimum bias data sample with an integrated luminosity of 7.1 inverse microbarns. Cross sections are measured differentially in terms of $\Delta \eta_F$, the larger of the pseudorapidity regions extending to the limits of the ATLAS sensitivity, at $\eta = \pm 4.9$, in which no final state particles are produced above a transverse momentum threshold $p_\perp$ cut. The measurements span the region $0 < \Delta \eta_F < 8$ for $200 < p_T\text{ cut} < 800 \text{MeV}$. At small $\Delta \eta_F$, the data test the reliability of hadronisation models in describing rapidity and transverse momentum fluctuations in final state particle production. The measurements at larger gap sizes are dominated by contributions from the single diffractive dissociation process ($pp \to Xp$), enhanced by double dissociation ($pp \to XY$) where the invariant mass of the lighter of the two dissociation systems satisfies $M_Y \lesssim 7 \text{GeV}$. The resulting cross section is $\mathrm{d} \sigma / \mathrm{d} \Delta \eta_F \sim 1$ mb for $\Delta \eta_F \gtrsim 3$. The large rapidity gap data are used to constrain the value of the pomeron intercept appropriate to triple Regge models of soft diffraction. The cross section integrated over all gap sizes is compared with other LHC inelastic cross section measurements. Source code: ATLAS_2012_I1084540.cc 1// -*- C++ -*-
2/**
3 * @name ATLAS Diffractive Gaps Rivet Analysis
4 * @author Tim Martin, tim.martin@cern.ch
5 * @version 1.0
6 * @date 16/01/2012
7 * @see http://arxiv.org/abs/1201.2808
8 * @note pp, sqrt(s) = 7 TeV
9 * @note Rapidity gap finding algorithm designed to compliment
10 * the ATLAS detector acceptance. Forward rapidity gap sizes
11 * are calculated for each event, considering all stable
12 * particles above pT cut values 200, 400, 600 and 800 MeV in
13 * turn. A forward rapidity gap is defined to be the largest
14 * continuous region stretching inward from either edge of the
15 * detector at eta = |4.9| which contains zero particles above
16 * pT Cut. Soft diffractive topologies are isolated at large
17 * gap sizes.
18 *
19 */
20#include "Rivet/Analysis.hh"
21#include "Rivet/Projections/FinalState.hh"
22
23namespace Rivet {
24
25
26 class ATLAS_2012_I1084540 : public Analysis {
27 public:
28
29 ATLAS_2012_I1084540() : Analysis("ATLAS_2012_I1084540") {}
30
31
32 /// @name Analysis methods
33 /// @{
34 /// Book histograms and initialise projections before the run
35 void init() {
36 //All final states. Rapidity range = ATLAS calorimetry. Lowest pT cut = 200 MeV.
37 const FinalState cnfs2((Cuts::etaIn(-_etaMax, _etaMax) && Cuts::pT >= 0.2 * GeV));
38 const FinalState cnfs4((Cuts::etaIn(-_etaMax, _etaMax) && Cuts::pT >= 0.4 * GeV));
39 const FinalState cnfs6((Cuts::etaIn(-_etaMax, _etaMax) && Cuts::pT >= 0.6 * GeV));
40 const FinalState cnfs8((Cuts::etaIn(-_etaMax, _etaMax) && Cuts::pT >= 0.8 * GeV));
41 declare(cnfs2, "CNFS2");
42 declare(cnfs4, "CNFS4");
43 declare(cnfs6, "CNFS6");
44 declare(cnfs8, "CNFS8");
45
46 _etaBinSize = (2. * _etaMax)/(double)_etaBins;
47
48 //Book histogram
49 book(_h_DeltaEtaF_200 ,1, 1, 1);
50 book(_h_DeltaEtaF_400 ,2, 1, 1);
51 book(_h_DeltaEtaF_600 ,3, 1, 1);
52 book(_h_DeltaEtaF_800 ,4, 1, 1);
53 }
54
55 private:
56 void fillMap(const FinalState& fs, bool* energyMap, double pTcut) {
57 // Fill true/false array by iterating over particles and compare their
58 // pT with pTcut
59 for (const Particle& p : fs.particles(cmpMomByEta)) {
60 int checkBin = -1;
61 double checkEta = -_etaMax;
62 while (1) {
63 checkEta += _etaBinSize;
64 ++checkBin;
65 if (p.eta() < checkEta) {
66 energyMap[checkBin] = (p.pT() > pTcut * GeV);
67 break;
68 }
69 }
70 }
71 }
72
73 public:
74 /// Perform the per-event analysis
75 void analyze(const Event& event) {
76 static unsigned int event_count = 0;
77 ++event_count;
78 const FinalState& fs2 = apply<FinalState>(event, "CNFS2");
79 const FinalState& fs4 = apply<FinalState>(event, "CNFS4");
80 const FinalState& fs6 = apply<FinalState>(event, "CNFS6");
81 const FinalState& fs8 = apply<FinalState>(event, "CNFS8");
82
83 // Set up Yes/No arrays for energy in each eta bin at each pT cut
84 bool energyMap_200[_etaBins];
85 bool energyMap_400[_etaBins];
86 bool energyMap_600[_etaBins];
87 bool energyMap_800[_etaBins];
88 for (int i = 0; i < _etaBins; ++i) {
89 energyMap_200[i] = false;
90 energyMap_400[i] = false;
91 energyMap_600[i] = false;
92 energyMap_800[i] = false;
93 }
94
95 // Veto bins based on final state particles > Cut (Where Cut = 200 - 800 MeV pT)
96 fillMap(fs2, energyMap_200, 0.2);
97 fillMap(fs4, energyMap_400, 0.4);
98 fillMap(fs6, energyMap_600, 0.6);
99 fillMap(fs8, energyMap_800, 0.8);
100
101 // Apply gap finding algorithm
102 // Detector layout follows...
103 // -Eta [Proton --- DetectorCSide --- DetectorBarrel --- DetectorASide --- Proton] +Eta
104 bool gapDirectionAt200 = false; //False is gap on C size, True is gap on A side.
105 double largestEdgeGap_200 = 0.;
106 double largestEdgeGap_400 = 0.;
107 double largestEdgeGap_600 = 0.;
108 double largestEdgeGap_800 = 0.;
109
110 for (int E = 200; E <= 800; E += 200) {
111 double EdgeGapSizeA = -1, EdgeGapSizeC = -1;
112 bool* energyMap = 0;
113 switch (E) {
114 case 200: energyMap = energyMap_200; break;
115 case 400: energyMap = energyMap_400; break;
116 case 600: energyMap = energyMap_600; break;
117 case 800: energyMap = energyMap_800; break;
118 }
119
120 // Look left to right
121 for (int a = 0; a < _etaBins; ++a) {
122 if (energyMap[a] == true) {
123 EdgeGapSizeA = (_etaBinSize * a);
124 break;
125 }
126 }
127
128 // And look right to left
129 for (int c = _etaBins-1; c >= 0; --c) {
130 if (energyMap[c] == true) {
131 EdgeGapSizeC = (2 * _etaMax) - (_etaBinSize * (c+1));
132 if (fuzzyEquals(EdgeGapSizeC, 4.47035e-08)) EdgeGapSizeC = 0.0;
133 break;
134 }
135 }
136 // Put your hands on your hips
137
138 // Find the largest gap
139 double largestEdgeGap = 0.;
140 if (E == 200) {
141 // If the 200 MeV pass, take the biggest of the two gaps. Make note of which side for higher pT cuts.
142 largestEdgeGap = std::max(EdgeGapSizeA,EdgeGapSizeC);
143 gapDirectionAt200 = (EdgeGapSizeA > EdgeGapSizeC);
144 } else {
145 // Use the direction from 200 MeV pass, most accurate measure of which side gap is on.
146 if (gapDirectionAt200) {
147 largestEdgeGap = EdgeGapSizeA;
148 }
149 else largestEdgeGap = EdgeGapSizeC;
150 }
151
152 // Check case of empty detector
153 if (largestEdgeGap < 0.0) largestEdgeGap = 2.0 * _etaMax;
154
155 // Fill bin centre
156 switch (E) {
157 case 200: _h_DeltaEtaF_200->fill(largestEdgeGap + _etaBinSize/2.); break;
158 case 400: _h_DeltaEtaF_400->fill(largestEdgeGap + _etaBinSize/2.); break;
159 case 600: _h_DeltaEtaF_600->fill(largestEdgeGap + _etaBinSize/2.); break;
160 case 800: _h_DeltaEtaF_800->fill(largestEdgeGap + _etaBinSize/2.); break;
161 }
162
163 if (E == 200) largestEdgeGap_200 = largestEdgeGap;
164 if (E == 400) largestEdgeGap_400 = largestEdgeGap;
165 if (E == 600) largestEdgeGap_600 = largestEdgeGap;
166 if (E == 800) largestEdgeGap_800 = largestEdgeGap;
167 }
168
169 // Algorithm result every 1000 events
170 if (event_count % 1000 == 0) {
171 for (int E = 200; E <= 800; E += 200) {
172 bool* energyMap = 0;
173 double largestEdgeGap = 0;
174 switch (E) {
175 case 200: energyMap = energyMap_200; largestEdgeGap = largestEdgeGap_200; break;
176 case 400: energyMap = energyMap_400; largestEdgeGap = largestEdgeGap_400; break;
177 case 600: energyMap = energyMap_600; largestEdgeGap = largestEdgeGap_600; break;
178 case 800: energyMap = energyMap_800; largestEdgeGap = largestEdgeGap_800; break;
179 }
180 MSG_DEBUG("Largest Forward Gap at pT Cut " << E << " MeV=" << largestEdgeGap
181 << " eta, NFinalState pT > 200 in ATLAS acceptance:" << fs2.particles().size());
182 std::string hitPattern = "Detector HitPattern=-4.9[";
183 for (int a = 0; a < _etaBins; ++a) {
184 if (energyMap[a] == true) hitPattern += "X";
185 else hitPattern += "_";
186 }
187 hitPattern += "]4.9";
188 MSG_DEBUG(hitPattern);
189 std::string gapArrow = " ";
190 if (!gapDirectionAt200) {
191 int drawSpaces = (int)(_etaBins - (largestEdgeGap/_etaBinSize) + 0.5);
192 for (int i = 0; i < drawSpaces; ++i) gapArrow += " ";
193 }
194 int drawArrows = (int)((largestEdgeGap/_etaBinSize) + 0.5);
195 for (int i = 0; i < drawArrows; ++i) gapArrow += "^";
196 MSG_DEBUG(gapArrow);
197 }
198 }
199 }
200
201 /// Normalise histograms after the run, Scale to cross section
202 void finalize() {
203 MSG_DEBUG("Cross Section=" << crossSection() / millibarn << "mb, SumOfWeights=" << sumOfWeights());
204 scale(_h_DeltaEtaF_200, (crossSection() / millibarn)/sumOfWeights());
205 scale(_h_DeltaEtaF_400, (crossSection() / millibarn)/sumOfWeights());
206 scale(_h_DeltaEtaF_600, (crossSection() / millibarn)/sumOfWeights());
207 scale(_h_DeltaEtaF_800, (crossSection() / millibarn)/sumOfWeights());
208 }
209 /// @}
210
211 private:
212 /// @name Histograms
213 /// @{
214 Histo1DPtr _h_DeltaEtaF_200;
215 Histo1DPtr _h_DeltaEtaF_400;
216 Histo1DPtr _h_DeltaEtaF_600;
217 Histo1DPtr _h_DeltaEtaF_800;
218 /// @}
219 /// @name Private variables
220 /// @{
221 static constexpr int _etaBins = 49;
222 static constexpr double _etaMax = 4.9;
223 double _etaBinSize;
224 /// @}
225 };
226
227 RIVET_DECLARE_PLUGIN(ATLAS_2012_I1084540);
228
229}
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