Rivet analyses referenceBELLE_2014_I1312626Mass and angular distributions in $\bar{B}^0\to J/\psi K^-\pi^+$Experiment: BELLE (KEKB) Inspire ID: 1312626 Status: VALIDATED NOHEPDATA Authors:
Beam energies: ANY Run details:
Measurement of mass and angular distributions in $\bar{B}^0\to J/\psi K^-\pi^+$. The data were read from the plots in the paper and the backgrounds given subtracted. Source code: BELLE_2014_I1312626.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 Bbar0 -> J/[psi K- pi+
10 class BELLE_2014_I1312626 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2014_I1312626);
15
16
17 /// @name Analysis methods
18 /// @{
19
20 /// Book histograms and initialise projections before the run
21 void init() {
22 // projections
23 UnstableParticles ufs = UnstableParticles(Cuts::abspid==511);
24 declare(ufs, "UFS");
25 DecayedParticles B0(ufs);
26 B0.addStable( 443);
27 declare(B0, "B0");
28 // histograms
29 for(unsigned int ix=0;ix<7;++ix)
30 book(_h_mass[ix],1,1,1+ix);
31 for(unsigned int ix=0;ix<2;++ix)
32 book(_h_angle[ix],2,1,1+ix);
33 }
34
35
36 /// Perform the per-event analysis
37 void analyze(const Event& event) {
38 static const map<PdgId,unsigned int> & mode = { { 211,1}, {-321,1}, { 443,1}};
39 static const map<PdgId,unsigned int> & modeCC = { {-211,1}, { 321,1}, { 443,1}};
40 DecayedParticles B0 = apply<DecayedParticles>(event, "B0");
41 for(unsigned int ix=0;ix<B0.decaying().size();++ix) {
42 int sign=1;
43 if (B0.decaying()[ix].pid()<0 && B0.modeMatches(ix,3,mode )) sign = 1;
44 if (B0.decaying()[ix].pid()>0 && B0.modeMatches(ix,3,modeCC)) sign =-1;
45 else continue;
46 const Particle & pip = B0.decayProducts()[ix].at( sign*211)[0];
47 const Particle & Km = B0.decayProducts()[ix].at(-sign*321)[0];
48 const Particle & JPsi = B0.decayProducts()[ix].at( 443)[0];
49 double mpiJ2 = (pip.momentum()+JPsi.momentum()).mass2();
50 double mKpi2 = (pip.momentum()+Km .momentum()).mass2();
51 if(mpiJ2<16.) _h_mass[0]->fill(mKpi2);
52 else if(mpiJ2<19.) _h_mass[1]->fill(mKpi2);
53 else _h_mass[2]->fill(mKpi2);
54 if(mKpi2<1.2) _h_mass[3]->fill(mpiJ2);
55 else if(mKpi2<2.05) _h_mass[4]->fill(mpiJ2);
56 else if(mKpi2<3.2 ) _h_mass[5]->fill(mpiJ2);
57 else _h_mass[6]->fill(mpiJ2);
58 // mass cuts for angular variables
59 if(mKpi2<1.2 || mpiJ2<16. || mpiJ2>19.) continue;
60 // helicity angle find J.psi leptonic children
61 if(JPsi.children().size()!=2) continue;
62 if(JPsi.children()[0].pid()!=-JPsi.children()[1].pid()) continue;
63 if(JPsi.children()[0].abspid()!=PID::EMINUS &&
64 JPsi.children()[0].abspid()!=PID::MUON) continue;
65 Particle lm = JPsi.children()[0];
66 Particle lp = JPsi.children()[1];
67 if(lm.pid()<0) swap(lm,lp);
68 LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(B0.decaying()[ix].momentum().betaVec());
69 FourMomentum ppsi = boost1.transform(JPsi.momentum());
70 Vector3 axis1 = -ppsi.p3().unit();
71 LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(ppsi.betaVec());
72 FourMomentum plp = boost2.transform(boost1.transform(lp.momentum()));
73 double cL = plp.p3().unit().dot(axis1);
74 _h_angle[0]->fill(cL);
75 Vector3 LTrans = plp.p3() - cL*plp.p3().mod()*axis1;
76 FourMomentum pKpi = pip.momentum()+Km.momentum();
77 LorentzTransform boost3 = LorentzTransform::mkFrameTransformFromBeta(pKpi.betaVec());
78 FourMomentum ppi = boost3.transform(boost1.transform(pip.momentum()));
79 double cPi = ppi.p3().unit().dot(axis1);
80 Vector3 PTrans = ppi.p3() - cPi*ppi.p3().mod()*axis1;
81 double phi = atan2(LTrans.cross(PTrans).dot(axis1), LTrans.dot(PTrans));
82 _h_angle[1]->fill(phi);
83 }
84 }
85
86
87 /// Normalise histograms etc., after the run
88 void finalize() {
89 for(unsigned int ix=0;ix<7;++ix)
90 normalize(_h_mass[ix],1.,false);
91 for(unsigned int ix=0;ix<2;++ix)
92 normalize(_h_angle[ix],1.,false);
93 }
94
95 /// @}
96
97
98 /// @name Histograms
99 /// @{
100 Histo1DPtr _h_mass[7],_h_angle[2];
101 /// @}
102 };
103
104
105 RIVET_DECLARE_PLUGIN(BELLE_2014_I1312626);
106
107}
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