Rivet analyses referenceLHCB_2018_I1665223Measurement of $pp$ inelastic cross-section at 13 TeV using prompt, long-lived particles in the LHCb fiducial phase-spaceExperiment: LHCB (LHC) Inspire ID: 1665223 Status: VALIDATED Authors:
Beam energies: (6500.0, 6500.0) GeV Run details:
LHCb measurement of the inelastic interaction cross-section in proton-proton collisions at $\sqrt{s}=13$ TeV. Events are selected if they contain at least one prompt long-lived charged particle with momentum $p > 2$ GeV$/c$ and pseudorapidity ($\eta$) in the range $2 < \eta < 5$. A particle is long-lived if its proper (mean) lifetime is larger than $0.3 \times 10^{-10}$ s, (proper $c\tau > 9$ mm) and it is prompt if it is produced directly in the $pp$ collision or if none of its ancestors is long-lived. This definition is recommended by the LHC Minimum Bias and Underlying Event working group. Prompt long-lived charged hadrons should be used themselves in vetoing events rather than their charged decay products (e.g. Sigma +/-, Xi and Omega decays are blocked). Source code: LHCB_2018_I1665223.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/ChargedFinalState.hh"
4
5namespace Rivet {
6
7
8 /// @brief Inelastic xsection in pp collisions at 13 TeV for charged particles in LHCb acceptance
9 class LHCB_2018_I1665223 : public Analysis {
10 public:
11
12 /// Constructor
13 RIVET_DEFAULT_ANALYSIS_CTOR(LHCB_2018_I1665223);
14
15
16 /// @name Analysis methods
17 /// @{
18
19 /// Book histograms and initialise projections before the run
20 void init() {
21
22 // Register projection
23 declare(ChargedFinalState(Cuts::etaIn(ETAMIN, ETAMAX)), "lbCFS");
24
25 // Book histogram
26 book(_h_ppInel, 1, 1, 1);
27 }
28
29
30 /// Perform the per-event analysis
31 void analyze(const Event& event) {
32
33 // Eliminate non-inelastic events and empty events in LHCb
34 const ChargedFinalState& cfs = apply<ChargedFinalState>(event, "lbCFS");
35 if (cfs.particles().size() == 0) vetoEvent;
36
37 for (const Particle& myp : cfs.particles()) {
38 if (hasLongLivedParent(myp)) continue;
39 if (!isLongLivedParticle(myp)) continue;
40 // Only particles with p > 2 GeV measured
41 if (myp.momentum().p() < PMIN) continue;
42 // Histo gets filled only for inelastic events (at least one prompt charged particle)
43 _h_ppInel->fill(sqrtS());
44 break;
45 }
46 }
47
48
49 /// Normalise histograms etc., after the run
50 void finalize() {
51 scale(_h_ppInel, crossSection()/millibarn/sumOfWeights()); // norm to cross section (one-sided LHCb)
52 }
53
54 /// @}
55
56
57 bool isLongLivedParticle(const Particle& p) {
58 // Stable long-lived final-state charged particles in LHCb
59 static const int stablePids[9] = {11,13,211,321,2212,3112,3222,3312,3334};
60 for (int stablePid : stablePids) {
61 if (p.abspid() == stablePid) return true;
62 }
63 return false;
64 }
65
66 bool hasLongLivedParent(const Particle& p) {
67 // List of PDG IDs for particle with lifetimes higher than 0.03 ns (3.E-11 s) - long lived particles according to LHC MB&UE WG
68 static const int longLivedPids[20] = {3334,3322,3312,3222,3122,3112,2212,2112,321,310,130,211,20022,480000000,11,12,13,14,16,22};
69 for (int longLivedPid : longLivedPids) {
70 if (p.hasParentWith(Cuts::abspid == longLivedPid)) return true;
71 }
72 return false;
73 }
74
75 /// @name Histogram
76 Histo1DPtr _h_ppInel;
77
78 /// Cut constants
79 const double ETAMIN = 2.0, ETAMAX = 5.0, PMIN = 2.0*GeV;
80
81 };
82
83
84 RIVET_DECLARE_PLUGIN(LHCB_2018_I1665223);
85
86}
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