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BABAR_2009_I810694

Mass distributions in $B^-\to D^+\pi^-\pi^-$
Experiment: BABAR (PEP-II)
Inspire ID: 810694
Status: VALIDATED NOHEPDATA
Authors:
  • Peter Richardson
References:
  • Phys.Rev.D 79 (2009) 112004
Beams: * *
Beam energies: ANY
Run details:
  • Any process producing B- mesons, originally Upsilon(4S) decays

Measurement of mass and angular distributions in $B^-\to D^+\pi^-\pi^-$. The data were read from the plots in the paper and may not be corrected for acceptance/efficiency, however the backgrounds given in the paper were subtracted.

Source code: BABAR_2009_I810694.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- > D+ pi-pi-
 10  class BABAR_2009_I810694 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2009_I810694);
 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      BP.addStable( 411);
 27      BP.addStable(-411);
 28      declare(BP, "BP");
 29      // histograms
 30      for(unsigned int ix=0;ix<3;++ix) {
 31	if(ix<2) book(_h_angle[ix],2,1,1+ix);
 32	book(_h_mass[ix],1,1,1+ix);
 33      }
 34    }
 35
 36
 37    /// Perform the per-event analysis
 38    void analyze(const Event& event) {
 39      static const map<PdgId,unsigned int> & mode   = { { -411,1},{ 211,2}};
 40      static const map<PdgId,unsigned int> & modeCC = { {  411,1},{-211,2}};
 41      DecayedParticles BP = apply<DecayedParticles>(event, "BP");
 42      // loop over particles
 43      for(unsigned int ix=0;ix<BP.decaying().size();++ix) {
 44	int sign=1;
 45      	if      (BP.modeMatches(ix,3,mode  )) sign= 1;
 46      	else if (BP.modeMatches(ix,3,modeCC)) sign=-1;
 47	else continue;
 48       	const Particle  & Dp  = BP.decayProducts()[ix].at(-sign*411)[0];
 49	const Particles & pim = BP.decayProducts()[ix].at( sign*211);
 50	_h_mass[2]->fill((pim[0].momentum()+pim[1].momentum()).mass2());
 51	// boost to B rest frame
 52	LorentzTransform boost =
 53	  LorentzTransform::mkFrameTransformFromBeta(BP.decaying()[ix]. momentum().betaVec());
 54	FourMomentum pD    = boost.transform(Dp.momentum());
 55	FourMomentum ppi[2] = {boost.transform(pim[0].momentum()),boost.transform(pim[1].momentum())};
 56	double m2Dpi[2];
 57	for(unsigned int ix=0;ix<2;++ix) {
 58	  m2Dpi[ix] = (pim[ix].momentum()+Dp.momentum()).mass2();
 59	  if( (m2Dpi[ix]>4.5 && m2Dpi[ix]<5.5) ||
 60	      (m2Dpi[ix]>5.9 && m2Dpi[ix]<6.2) ) {
 61	    FourMomentum pDpi = pD+pim[ix];
 62	    LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pDpi.betaVec());
 63	    Vector3 axis1 = boost2.transform(ppi[ix]).p3().unit();
 64	    Vector3 axis2 = (ix==0 ? ppi[1] : ppi[0]).p3().unit();
 65	    double cTheta = axis1.dot(axis2);
 66	    if(m2Dpi[ix]<5.5)
 67	      _h_angle[0]->fill(cTheta);
 68	    else
 69	      _h_angle[1]->fill(cTheta);
 70	  }
 71	}
 72	if(m2Dpi[0]>m2Dpi[1]) {
 73	  _h_mass[1]->fill(m2Dpi[0]);
 74	  _h_mass[0]->fill(m2Dpi[1]);
 75	}
 76	else {
 77	  _h_mass[0]->fill(m2Dpi[0]);
 78	  _h_mass[1]->fill(m2Dpi[1]);
 79	}
 80      }
 81    }
 82
 83
 84    /// Normalise histograms etc., after the run
 85    void finalize() {
 86      for(unsigned int ix=0;ix<3;++ix) {
 87	if(ix<2) normalize(_h_angle[ix],1.,false);
 88	normalize(_h_mass[ix],1.,false);
 89      }
 90    }
 91
 92    /// @}
 93
 94
 95    /// @name Histograms
 96    /// @{
 97    Histo1DPtr _h_mass[3],_h_angle[2];
 98    /// @}
 99
100
101  };
102
103
104  RIVET_DECLARE_PLUGIN(BABAR_2009_I810694);
105
106}