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BESIII_2019_I1702549

$D_s^+\to K^0 e^+\nu_e$ $q^2$ spectrum $D_s^+\to K^{*0} e^+\nu_e$ $q^2$ distributions
Experiment: BESIII (BEPC)
Inspire ID: 1702549
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Phys.Rev.Lett. 122 (2019) 6, 061801
Beams: * *
Beam energies: ANY
Run details:
  • Any process producing D_s+

Measurement of the $q^2$ spectrum in the decay $D_s^+\to K^0 e^+\nu_e$ and kinematic distributions in $D_s^+\to K^{*0} e^+\nu_e$ $q^2$ by BES-III. N.B. the plots where read from the paper and may not have been corrected for acceptance.

Source code: BESIII_2019_I1702549.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 q^2 in D_s+ -> K0 e+ nu_e and ->K*0 e+ nu_e distributions
 10  class BESIII_2019_I1702549 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2019_I1702549);
 15
 16
 17    /// @name Analysis methods
 18    /// @{
 19
 20    /// Book histograms and initialise projections before the run
 21    void init() {
 22
 23      // Initialise and register projections
 24      UnstableParticles ufs = UnstableParticles(Cuts::pid==431);
 25      declare(ufs, "UFS");
 26      DecayedParticles DS(ufs);
 27      DS.addStable(PID::PI0);
 28      DS.addStable(PID::K0S);
 29      DS.addStable(PID::ETA);
 30      DS.addStable(PID::ETAPRIME);
 31      declare(DS, "DS");
 32
 33      // Book histograms
 34      book(_h_q2, 1, 1, 1);
 35      book(_nD,"/TMP/nD");
 36      for(unsigned int ix=0;ix<5;++ix)
 37	book(_h_Kstar[ix],1,1,3+ix);
 38    }
 39
 40    /// Perform the per-event analysis
 41    void analyze(const Event& event) {
 42      static const map<PdgId,unsigned int> & mode1 = { { 310,1}, {-11,1}, { 12,1}};
 43      static const map<PdgId,unsigned int> & mode2 = { { 130,1}, {-11,1}, { 12,1}};
 44      static const map<PdgId,unsigned int> & mode3 = { { 311,1}, {-11,1}, { 12,1}};
 45      static const map<PdgId,unsigned int> & mode4 = { { 321,1}, {-211,1}, {-11,1}, { 12,1}};
 46      DecayedParticles DS = apply<DecayedParticles>(event, "DS");
 47      // loop over particles
 48      for(unsigned int ix=0;ix<DS.decaying().size();++ix) {
 49        _nD->fill();
 50        if(DS.modeMatches(ix,3,mode1)) {
 51          _h_q2->fill((DS.decaying()[ix].momentum()-DS.decayProducts()[ix].at(310)[0].momentum()).mass2());
 52        }
 53        else if(DS.modeMatches(ix,3,mode2)) {
 54          _h_q2->fill((DS.decaying()[ix].momentum()-DS.decayProducts()[ix].at(130)[0].momentum()).mass2());
 55        }
 56        else if(DS.modeMatches(ix,3,mode3)) {
 57          _h_q2->fill((DS.decaying()[ix].momentum()-DS.decayProducts()[ix].at(311)[0].momentum()).mass2());
 58        }
 59        else if(DS.modeMatches(ix,4,mode4)) {
 60          const Particle & Kp = DS.decayProducts()[ix].at( 321)[0];
 61          const Particle & pim= DS.decayProducts()[ix].at(-211)[0];
 62          const Particle & ep = DS.decayProducts()[ix].at(-11)[0];
 63          const Particle & nue= DS.decayProducts()[ix].at( 12)[0];
 64          FourMomentum pKstar = Kp.momentum()+pim.momentum();
 65          _h_Kstar[0]->fill(pKstar.mass());
 66          FourMomentum qq = DS.decaying()[ix].momentum()-pKstar;
 67          _h_Kstar[1]->fill(qq.mass2());
 68          // boost momenta to Ds rest frame
 69          LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(DS.decaying()[ix].momentum().betaVec());
 70          FourMomentum pKS = boost.transform(pKstar);
 71          Matrix3 ptoz(-pKS.p3().unit(), Vector3(0,0,1));
 72          boost.preMult(ptoz);
 73          // the momenta in frane to W along z
 74          FourMomentum pD  = boost.transform(DS.decaying()[ix].momentum());
 75          FourMomentum pK  = boost.transform(Kp .momentum());
 76          FourMomentum ppi = boost.transform(pim.momentum());
 77          FourMomentum pe  = boost.transform(ep .momentum());
 78          FourMomentum pnu = boost.transform(nue.momentum());
 79          pKstar = pK+ppi;
 80          qq = pD-pKstar;
 81          LorentzTransform boostK = LorentzTransform::mkFrameTransformFromBeta(pKstar.betaVec());
 82          Vector3 axisK = boostK.transform(pK).p3().unit();
 83          _h_Kstar[3]->fill(axisK.dot(pKstar.p3().unit()));
 84          LorentzTransform boostW = LorentzTransform::mkFrameTransformFromBeta(    qq.betaVec());
 85          Vector3 axisE = boostW.transform(pe).p3().unit();
 86          _h_Kstar[2]->fill(axisE.dot(qq.p3().unit()));
 87          axisK.setZ(0.);
 88          axisE.setZ(0.);
 89          double chi = atan2(axisE.cross(axisK).dot(qq.p3().unit()), axisE.dot(axisK));
 90          _h_Kstar[4]->fill(chi);
 91        }
 92      }
 93    }
 94
 95
 96    /// Normalise histograms etc., after the run
 97    void finalize() {
 98      // normalise to width in inverse ns
 99      scale(_h_q2, 1./0.504e-3/ *_nD);
100      for (unsigned int ix=0;ix<5;++ix) {
101        normalize(_h_Kstar[ix]);
102      }
103    }
104
105    /// @}
106
107
108    /// @name Histograms
109    /// @{
110    Histo1DPtr _h_q2;
111    Histo1DPtr _h_Kstar[5];
112    CounterPtr _nD;
113    /// @}
114
115
116  };
117
118
119  RIVET_DECLARE_PLUGIN(BESIII_2019_I1702549);
120
121}