Rivet analyses referenceH1_2009_I810046Strangeness Production at low $Q^2$ in Deep-Inelastic $ep$ Scattering at HERAExperiment: H1 (HERA) Inspire ID: 810046 Status: VALIDATED Authors:
Beam energies: (159.0, 159.0) GeV Run details:
The production of neutral strange hadrons is investigated using deep-inelastic scattering events measured with the H1 detector at HERA. The measurements are made in the phase space defined by the negative four-momentum transfer squared of the photon $2 < Q^2 < 100 GeV^2$ and the inelasticity $0.1 < y < 0.6$. The $K_s$ and $\Lambda$ production cross sections and their ratios are determined. $K_s$ production is compared to the production of charged particles in the same region of phase space. The $\Lambda$ - anti-$\Lambda$ asymmetry is also measured and found to be consistent with zero. Predictions of leading order Monte Carlo programs are compared to the data. Source code: H1_2009_I810046.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/FinalState.hh"
4#include "Rivet/Projections/DISKinematics.hh"
5#include "Rivet/Projections/UnstableParticles.hh"
6
7namespace Rivet {
8
9
10 /// @brief Cross-sections of \f$K_{0}$\f and \f$\Lambda$\f in DIS
11 class H1_2009_I810046 : public Analysis {
12 public:
13
14 /// Constructor
15 RIVET_DEFAULT_ANALYSIS_CTOR(H1_2009_I810046);
16
17
18 /// @name Analysis methods
19 /// @{
20
21 /// Book histograms and initialise projections before the run
22 void init() {
23 const DISKinematics& diskin = DISKinematics();
24 declare(diskin, "Kinematics");
25 declare(UnstableParticles(), "UPS");
26
27 book(_h_K0S_q2, 4, 1, 1);
28 book(_h_K0S_x, 5, 1, 1);
29 book(_h_K0S_pt, 6, 1, 1);
30 book(_h_K0S_eta, 7, 1, 1);
31
32 book(_h_LAMBDA_q2, 8, 1, 1);
33 book(_h_LAMBDA_x, 9, 1, 1);
34 book(_h_LAMBDA_pt, 10, 1, 1);
35 book(_h_LAMBDA_eta, 11, 1, 1);
36
37 }
38
39
40 /// Perform the per-event analysis
41 void analyze(const Event& event) {
42 /// DIS kinematics
43 const DISKinematics& dk = apply<DISKinematics>(event, "Kinematics");
44 const double q2 = dk.Q2();
45 const double x = dk.x();
46 const double y = dk.y();
47 const int orientation = dk.orientation();
48
49 if (!inRange(q2/GeV2, 2.0, 100.0)) vetoEvent;
50 if (!inRange(y, 0.1, 0.6)) vetoEvent;
51 const UnstableParticles& ufs = apply<UnstableParticles>(event, "UPS");
52
53 for (const Particle& p: select(ufs.particles(), Cuts::abspid == abs(PID::K0S))) {
54 if (!inRange(p.pt()/GeV, 0.5, 3.5)) continue;
55 if (!inRange(p.eta(), -1.3, 1.3)) continue;
56 _h_K0S_q2->fill(q2/GeV2);
57 _h_K0S_x->fill(x);
58 _h_K0S_pt->fill(p.pt()/GeV);
59 _h_K0S_eta->fill(p.eta()*orientation);
60 }
61
62 for (const Particle& p: select(ufs.particles(), Cuts::abspid == abs(PID::LAMBDA))) {
63 if (!inRange(p.pt()/GeV, 0.5, 3.5)) continue;
64 if (!inRange(p.eta(), -1.3, 1.3)) continue;
65 _h_LAMBDA_q2->fill(q2/GeV2);
66 _h_LAMBDA_x->fill(x);
67 _h_LAMBDA_pt->fill(p.pt()/GeV);
68 _h_LAMBDA_eta->fill(p.eta()*orientation);
69 }
70 }
71
72
73 /// Normalise histograms etc., after the run
74 void finalize() {
75 const double sf = crossSection()/nanobarn/sumOfWeights();
76 scale( _h_K0S_pt, sf);
77 scale( _h_K0S_eta, sf);
78 scale( _h_K0S_q2, sf);
79 scale( _h_K0S_x, sf/1000);
80
81 scale( _h_LAMBDA_pt, sf);
82 scale( _h_LAMBDA_eta, sf);
83 scale( _h_LAMBDA_q2, sf);
84 scale( _h_LAMBDA_x, sf/1000);
85 }
86
87 /// @}
88
89 /// @name Histograms
90 /// @}
91 Histo1DPtr _h_K0S_pt, _h_K0S_eta, _h_K0S_x, _h_K0S_q2;
92 Histo1DPtr _h_LAMBDA_pt, _h_LAMBDA_eta, _h_LAMBDA_x, _h_LAMBDA_q2;
93 /// @}
94
95 };
96
97
98 RIVET_DECLARE_PLUGIN(H1_2009_I810046);
99
100}
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