Rivet analyses referenceARGUS_1994_I375417Pion helicity angle in τ−→π−π0ντExperiment: ARGUS (DORIS) Inspire ID: 375417 Status: VALIDATED NOHEPDATA Authors:
Beam energies: ANY Run details:
Measurement of the pion helicity angle in the π−π0 frame for τ−→π−π0ντ. The corrected data were read from figure 3 in the paper. Source code: ARGUS_1994_I375417.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/UnstableParticles.hh"
4#include "Rivet/Projections/DecayedParticles.hh"
5#include "Rivet/Tools/HistoGroup.hh"
6
7namespace Rivet {
8
9
10 /// @brief tau -> pi- pi0 nu_tau
11 class ARGUS_1994_I375417 : public Analysis {
12 public:
13
14 /// Constructor
15 RIVET_DEFAULT_ANALYSIS_CTOR(ARGUS_1994_I375417);
16
17
18 /// @name Analysis methods
19 /// @{
20
21 /// Book histograms and initialise projections before the run
22 void init() {
23 // Initialise and register projections
24 UnstableParticles ufs = UnstableParticles(Cuts::abspid==15);
25 declare(ufs, "UFS");
26 DecayedParticles TAU(ufs);
27 TAU.addStable(310);
28 TAU.addStable(111);
29 TAU.addStable(221);
30 declare(TAU, "TAU");
31 // histos
32 book(_b, {0.5, 0.69, 0.776, 0.85, 1.1});
33 for (auto& b : _b->bins()) {
34 book(b, 1, 1, b.index());
35 }
36 }
37
38
39 /// Perform the per-event analysis
40 void analyze(const Event& event) {
41 DecayedParticles TAU = apply<DecayedParticles>(event, "TAU");
42 // loop over particles
43 for (unsigned int ix=0; ix<TAU.decaying().size(); ++ix) {
44 int sign = TAU.decaying()[ix].pid()>0 ? 1 : -1;
45 if (!(TAU.modeMatches(ix,3,mode) || TAU.modeMatches(ix,3,modeCC))) continue;
46 const Particle& pi0 = TAU.decayProducts()[ix].at( 111 )[0];
47 const Particle& pim = TAU.decayProducts()[ix].at(-211*sign)[0];
48 FourMomentum phad = pim.mom()+pi0.mom();
49 LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(TAU.decaying()[ix].mom().betaVec());
50 phad = boost.transform(phad);
51 LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(phad.betaVec());
52 FourMomentum ppi = boost2.transform(boost.transform(pim.mom()));
53 const double cAlpha = ppi.p3().unit().dot(phad.p3().unit());
54 _b->fill(phad.mass(),cAlpha);
55 }
56 }
57
58
59 /// Normalise histograms etc., after the run
60 void finalize() {
61 normalize(_b, 1.0, false);
62 }
63
64 /// @}
65
66
67 /// @name Histograms
68 /// @{
69 Histo1DGroupPtr _b;
70 const map<PdgId,unsigned int> mode = { { 111,1},{-211,1},{ 16,1}};
71 const map<PdgId,unsigned int> modeCC = { { 111,1},{ 211,1},{-16,1}};
72 /// @}
73
74
75 };
76
77
78 RIVET_DECLARE_PLUGIN(ARGUS_1994_I375417);
79
80}
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