Rivet analyses referenceBABAR_2009_I813140$\pi^+\pi^-$ mass distriubution in $B^+\to\pi^+\pi^+\pi^-$Experiment: BABAR (PEP-II) Inspire ID: 813140 Status: VALIDATED NOHEPDATA Authors:
Beam energies: ANY Run details:
Measurement of the $\pi^+\pi^-$ mass distriubutions in $B^+\to\pi^+\pi^+\pi^-$. The data were read from the plotsi in the paper and may not be corrected for efficiency/acceptable, although the backgrounds given in the paper have been subtracted. Source code: BABAR_2009_I813140.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/UnstableParticles.hh"
4#include "Rivet/Projections/DecayedParticles.hh"
5
6namespace Rivet {
7
8
9 /// @brief B+ -> pi+ pi+ pi-
10 class BABAR_2009_I813140 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2009_I813140);
15
16
17 /// @name Analysis methods
18 /// @{
19
20 /// Book histograms and initialise projections before the run
21 void init() {
22 // Initialise and register projections
23 UnstableParticles ufs = UnstableParticles(Cuts::abspid==521);
24 declare(ufs, "UFS");
25 DecayedParticles BP(ufs);
26 declare(BP, "BP");
27 // histograms
28 book(_h_all,1,1,1);
29 for(unsigned int ix=0;ix<3;++ix)
30 for(unsigned int iy=0;iy<2;++iy)
31 book(_h_charge[ix][iy],2,1+ix,1+iy);
32 }
33
34
35 /// Perform the per-event analysis
36 void analyze(const Event& event) {
37 static const map<PdgId,unsigned int> & mode = { { -211,1},{ 211,2}};
38 static const map<PdgId,unsigned int> & modeCC = { { 211,1},{-211,2}};
39 DecayedParticles BP = apply<DecayedParticles>(event, "BP");
40 // loop over particles
41 for(unsigned int ix=0;ix<BP.decaying().size();++ix) {
42 int sign=1;
43 if (BP.modeMatches(ix,3,mode )) sign= 1;
44 else if (BP.modeMatches(ix,3,modeCC)) sign=-1;
45 else continue;
46 // particles
47 const Particle & pim = BP.decayProducts()[ix].at(-sign*211)[0];
48 const Particles & pip = BP.decayProducts()[ix].at( sign*211);
49 // boost to B rest frame
50 LorentzTransform boost =
51 LorentzTransform::mkFrameTransformFromBeta(BP.decaying()[ix]. momentum().betaVec());
52 FourMomentum pPim = boost.transform(pim.momentum());
53 FourMomentum pPip[2];
54 for(unsigned int ix=0;ix<2;++ix) pPip[ix] = boost.transform(pip[ix].momentum());
55 // loop over pi+
56 for(unsigned int ix=0;ix<2;++ix) {
57 FourMomentum ppipi = pip[ix].momentum()+pim.momentum();
58 double mpipi = ppipi.mass();
59 _h_all->fill(mpipi);
60 _h_charge[0][(1-sign)/2]->fill(mpipi);
61 unsigned int ibatch = ix==0 ? 1 : 0;
62 Vector3 axis = pPip[ibatch].p3().unit();
63 LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(ppipi.betaVec());
64 Vector3 axis2 = boost1.transform(pPim).p3().unit();
65 double cTheta = axis.dot(axis2);
66 if(cTheta>0) {
67 _h_charge[1][(1-sign)/2]->fill(mpipi);
68 }
69 else {
70 _h_charge[2][(1-sign)/2]->fill(mpipi);
71 }
72 }
73 }
74 }
75
76
77 /// Normalise histograms etc., after the run
78 void finalize() {
79 normalize(_h_all,1.,false);
80 for(unsigned int ix=0;ix<3;++ix)
81 for(unsigned int iy=0;iy<2;++iy)
82 normalize(_h_charge[ix][iy],1.,false);
83 }
84
85 /// @}
86
87
88 /// @name Histograms
89 /// @{
90 Histo1DPtr _h_all,_h_charge[3][2];
91 /// @}
92
93
94 };
95
96
97 RIVET_DECLARE_PLUGIN(BABAR_2009_I813140);
98
99}
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