1// -*- C++ -*-
  2#include "Rivet/Analysis.hh"
  3#include "Rivet/Projections/Beam.hh"
  4#include "Rivet/Projections/UnstableParticles.hh"
  5
  6namespace Rivet {
  7
  8
  9  /// @brief J/psi polarization at 7 TeV
 10  class LHCB_2013_I1244315 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(LHCB_2013_I1244315);
 15
 16
 17    /// @name Analysis methods
 18    /// @{
 19
 20    /// Book histograms and initialise projections before the run
 21    void init() {
 22      // projections
 23      declare(Beam(), "Beams");
 24      declare(UnstableParticles(), "UFS");
 25      // histograms
 26      // cross section
 27      _ybins={2.0,2.5,3.0,3.5,4.0,4.5};
 28      book(_h_Jpsi,_ybins);
 29      for(unsigned int iy=0;iy<5;++iy) {
 30	book(_h_Jpsi->bin(iy+1),4,1,1+iy);
 31	for(unsigned int ix=0;ix<2;++ix) {
 32	  for(unsigned int iz=0;iz<3;++iz) {
 33	    string name="TMP/POL_"+toString(ix)+"_"+toString(iy)+"_"+toString(iz);
 34	    book(_p_Jpsi[ix][iy][iz],name,refData(1+ix,1,1+iy));
 35	  }
 36	}
 37      }
 38    }
 39
 40    void findDecayProducts(const Particle & mother, unsigned int & nstable,  
 41                           Particles & mup, Particles & mum) {
 42      for(const Particle & p : mother.children()) {
 43        int id = p.pid();
 44        if (id == PID::MUON ) {
 45          ++nstable;
 46    	  mum.push_back(p);
 47    	}
 48        else if (id == PID::ANTIMUON) {
 49          ++nstable;
 50    	  mup.push_back(p);
 51        }
 52        else if (id == PID::PI0 || id == PID::K0S || id == PID::K0L ) {
 53          ++nstable;
 54        }
 55        else if ( !p.children().empty() ) {
 56          findDecayProducts(p, nstable, mup, mum);
 57        }
 58        else
 59          ++nstable;
 60      }
 61    }
 62
 63    /// Perform the per-event analysis
 64    void analyze(const Event& event) {
 65      // find the beams
 66      const ParticlePair & beams = apply<Beam>(event, "Beams").beams();
 67      // Final state of unstable particles to get particle spectra
 68      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
 69      for (const Particle& p : ufs.particles(Cuts::pid==443)) {
 70	// prompt
 71	if(p.fromBottom()) continue;
 72      	// pT and rapidity
 73      	double rapidity = p.rapidity();
 74      	double xp = p.perp();
 75	// cross section
 76	_h_Jpsi->fill(rapidity,xp);
 77	// polarization
 78      	unsigned int nstable=0;
 79      	Particles mup,mum;
 80      	findDecayProducts(p,nstable,mup,mum);
 81      	if(mup.size()!=1 || mum.size()!=1 || nstable!=2) continue;
 82	// find the rapidity interval
 83	if(rapidity<=2. || rapidity>=4.5) continue;
 84	unsigned int iy=0;
 85	for(iy=0;iy<5;++iy) if(rapidity<_ybins[iy+1]) break;
 86	// first the CS frame
 87	// first boost so upslion momentum =0 in z direction
 88	Vector3 beta = p.momentum().betaVec();
 89	beta.setX(0.);beta.setY(0.);
 90	LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(beta);
 91	FourMomentum pp = boost.transform(p.momentum());
 92	// and then transverse so pT=0
 93        beta = pp.betaVec();
 94	LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(beta);
 95	// get all the momenta in this frame
 96	Vector3 muDirn = boost2.transform(boost.transform(mup[0].momentum())).p3().unit();
 97	FourMomentum p1 = boost2.transform(boost.transform(beams. first.momentum()));
 98	FourMomentum p2 = boost2.transform(boost.transform(beams.second.momentum()));
 99	if(beams.first.momentum().z()<0.) swap(p1,p2);
100	if(p.rapidity()<0.) swap(p1,p2);
101	Vector3 axisy = (p1.p3().cross(p2.p3())).unit();
102	Vector3 axisz(0.,0.,1.);
103	Vector3 axisx = axisy.cross(axisz);
104	double cTheta = axisz.dot(muDirn);
105	double cPhi   = axisx.dot(muDirn);
106	// fill the moments
107	_p_Jpsi[1][iy][0]->fill(xp, 1.25*(3.*sqr(cTheta)-1.));
108	_p_Jpsi[1][iy][1]->fill(xp, 1.25*(1.-sqr(cTheta))*(2.*sqr(cPhi)-1.));
109	_p_Jpsi[1][iy][2]->fill(xp, 2.5 *cTheta*sqrt(1.-sqr(cTheta))*cPhi);
110	// now for the HX frame
111	beta = p.momentum().betaVec();
112	boost = LorentzTransform::mkFrameTransformFromBeta(beta);
113	axisz = pp.p3().unit();
114	axisx = axisy.cross(axisz);
115	cTheta = axisz.dot(muDirn);
116	cPhi   = axisx.dot(muDirn);
117	// fill the moments
118	_p_Jpsi[0][iy][0]->fill(xp, 1.25*(3.*sqr(cTheta)-1.));
119	_p_Jpsi[0][iy][1]->fill(xp, 1.25*(1.-sqr(cTheta))*(2.*sqr(cPhi)-1.));
120	_p_Jpsi[0][iy][2]->fill(xp, 2.5 *cTheta*sqrt(1.-sqr(cTheta))*cPhi);
121      }
122    }
123
124
125    /// Normalise histograms etc., after the run
126    void finalize() {
127      double factor = crossSection()/nanobarn/sumOfWeights();
128      scale(_h_Jpsi,factor);
129      divByGroupWidth(_h_Jpsi);
130      for(unsigned int iy=0;iy<5;++iy) {
131	// Loop over frame definition
132	for(unsigned int iframe=0;iframe<2;++iframe) {
133          // book scatters
134          Estimate1DPtr lTheta,lPhi,lThetaPhi;
135          book(lTheta   ,iframe+1,1,1+iy);
136          book(lPhi     ,iframe+1,3,1+iy);
137          book(lThetaPhi,iframe+1,2,1+iy);
138	  // histos for the moments
139	  Profile1DPtr moment[3];
140	  for(unsigned int ix=0;ix<3;++ix)
141	    moment[ix] = _p_Jpsi[iframe][iy][ix];
142	  // loop over bins
143	  for(unsigned int ibin=1;ibin<=moment[0]->bins().size();++ibin) {
144            // extract moments and errors
145            double val[3],err[3];
146            // m1 = lTheta/(3+lTheta), m2 = lPhi/(3+lTheta), m3 = lThetaPhi/(3+lTheta)
147	    for(unsigned int ix=0;ix<3;++ix) {
148	      val[ix] = moment[ix]->bins()[ibin].numEntries()>0 && moment[ix]->bins()[ibin].effNumEntries()>0 ? moment[ix]->bins()[ibin].mean(2)   : 0.;
149	      err[ix] = moment[ix]->bins()[ibin].numEntries()>1 && moment[ix]->bins()[ibin].effNumEntries()>1 ? moment[ix]->bins()[ibin].stdErr(2) : 0.;
150	    }
151	    // values of the lambdas and their errors
152	    double l1 = 3.*val[0]/(1.-val[0]);
153	    double e1 = 3./sqr(1.-val[0])*err[0];
154	    double l2 = (3.+l1)*val[1];
155	    double e2 = 3./sqr(1.-val[0])*sqrt(sqr(err[0]*val[1])+sqr(err[1]*(1.-val[0])));
156	    double l3 = (3.+l1)*val[2];
157	    double e3 = 3./sqr(1.-val[0])*sqrt(sqr(err[0]*val[1])+sqr(err[1]*(1.-val[0])));
158	    // fill the scatters
159	    lTheta   ->bin(ibin).setVal(l1);
160            lTheta   ->bin(ibin).setErr(make_pair(e1,e1));
161	    lPhi     ->bin(ibin).setVal(l2);
162	    lPhi     ->bin(ibin).setErr(make_pair(e2,e2));
163	    lThetaPhi->bin(ibin).setVal(l3);
164	    lThetaPhi->bin(ibin).setErr(make_pair(e3,e3));
165	  }
166       	}
167      }
168    }
169    /// @}
170
171
172    /// @name Histograms
173    /// @{
174    Profile1DPtr _p_Jpsi[2][5][3];
175    Histo1DGroupPtr _h_Jpsi;
176    vector<double>  _ybins;
177    /// @}
178
179
180  };
181
182
183  RIVET_DECLARE_PLUGIN(LHCB_2013_I1244315);
184
185}