Rivet analyses referenceBELLE_2016_I1283183Lepton Forward-Backward Asymmetry in $B\to X_s\ell^+\ell^-$Experiment: BELLE (KEKB) Inspire ID: 1283183 Status: VALIDATED Authors:
Beam energies: ANY Run details:
Measurement of the lepton forward-backward asymmetry in $B\to X_s\ell^+\ell^-$ in 4 $q^2$ bins. Source code: BELLE_2016_I1283183.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/UnstableParticles.hh"
4
5namespace Rivet {
6
7
8 /// @brief B -> Xs l+l-
9 class BELLE_2016_I1283183 : public Analysis {
10 public:
11
12 /// Constructor
13 RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2016_I1283183);
14
15
16 /// @name Analysis methods
17 /// @{
18
19 /// Book histograms and initialise projections before the run
20 void init() {
21 // Initialise and register projections
22 declare(UnstableParticles(Cuts::abspid==521 || Cuts::abspid==511), "UFS");
23 // book the profile hist
24 book(_p,2,1,1);
25 }
26
27 void findDecayProducts(bool & charm, const Particle& mother,
28 unsigned int& nK0, unsigned int& nKp,
29 unsigned int& nKm, Particles & lp, Particles & lm) {
30 for (const Particle & p : mother.children()) {
31 int id = p.pid();
32 if(PID::isCharmHadron(p.pid())) charm = true;
33 else if ( id == PID::POSITRON || id == PID::ANTIMUON) lp.push_back(p);
34 else if ( id == PID::ELECTRON || id == PID::MUON ) lm.push_back(p);
35 else if ( id == PID::KPLUS ) ++nKp;
36 else if (id == PID::KMINUS ) ++nKm;
37 else if (id == PID::K0S) ++nK0;
38 else if (id == PID::PI0 || id == PID::PIPLUS || id == PID::PIMINUS) {
39 continue;
40 }
41 else if ( !p.children().empty() ) {
42 findDecayProducts(charm, p, nK0, nKp, nKm,lp,lm);
43 }
44 }
45 }
46
47 /// Perform the per-event analysis
48 void analyze(const Event& event) {
49 // Loop over bottoms
50 for (const Particle& bottom : apply<UnstableParticles>(event, "UFS").particles()) {
51 // remove mixing entries etc
52 if(bottom.children()[0].abspid()==bottom.abspid()) continue;
53 bool charm = false;
54 Particles lp,lm;
55 unsigned int nK0(0),nKp(0),nKm(0);
56 findDecayProducts(charm,bottom, nK0, nKp, nKm,lp,lm);
57 if(charm) continue;
58 unsigned int nk = nKp-nKm+nK0;
59 if( nk % 2 == 0) continue;
60 if (lp.size()!=1 || lm.size()!=1 || lp[0].pid()!=-lm[0].pid()) continue;
61 if(bottom.pid()>0) swap(lp,lm);
62 double q2 = (lp[0].momentum()+lm[0].momentum()).mass2();
63 // veto region valid for muons but not electrons
64 if(lm[0].pid()==PID::ELECTRON && ( (q2>7.3 && q2<8.1) || (q2>11.8 && q2<12.5) )) continue;
65 // first boost to bottom frame
66 const LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(bottom.momentum().betaVec());
67 FourMomentum plp = boost.transform(lp[0] .momentum());
68 FourMomentum plm = boost.transform(lm[0] .momentum());
69 FourMomentum pB = boost.transform(bottom.momentum());
70 const LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta((plp+plm).betaVec());
71 plp = boost2.transform(plp);
72 pB = boost .transform(pB );
73 double cTheta = plp.p3().unit().dot(pB.p3().unit());
74 _p->fill(q2, cTheta>0 ? 1 : -1);
75 }
76 }
77
78
79 /// Normalise histograms etc., after the run
80 void finalize() {
81 }
82
83 /// @}
84
85
86 /// @name Histograms
87 /// @{
88 Profile1DPtr _p;
89 /// @}
90
91
92 };
93
94
95 RIVET_DECLARE_PLUGIN(BELLE_2016_I1283183);
96
97}
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