diff --git a/analyses/pluginBES/BESIII_2012_I1113599.cc b/analyses/pluginBES/BESIII_2012_I1113599.cc
--- a/analyses/pluginBES/BESIII_2012_I1113599.cc
+++ b/analyses/pluginBES/BESIII_2012_I1113599.cc
@@ -1,130 +1,131 @@
 // -*- C++ -*-
 #include "Rivet/Analysis.hh"
 #include "Rivet/Projections/Beam.hh"
 #include "Rivet/Projections/FinalState.hh"
+#include "Rivet/Projections/UnstableParticles.hh"
 
 namespace Rivet {
 
 
   /// @brief J/psi to p pbar n nbar
   class BESIII_2012_I1113599 : public Analysis {
   public:
 
     /// Constructor
     DEFAULT_RIVET_ANALYSIS_CTOR(BESIII_2012_I1113599);
 
 
     /// @name Analysis methods
     //@{
 
     /// Book histograms and initialise projections before the run
     void init() {
 
       // Initialise and register projections
       declare(Beam(), "Beams");
       declare(UnstableParticles(), "UFS");
       declare(FinalState(), "FS");
 
       // Book histograms
       book(_h_proton , "ctheta_p",20,-1.,1.);
       book(_h_neutron, "ctheta_n",20,-1.,1.);
 
     }
 
 
     /// Perform the per-event analysis
     void analyze(const Event& event) {
       // get the axis, direction of incoming electron
       const ParticlePair& beams = apply<Beam>(event, "Beams").beams();
       Vector3 axis;
       if(beams.first.pid()>0)
 	axis = beams.first .momentum().p3().unit();
       else
 	axis = beams.second.momentum().p3().unit();
       // types of final state particles
       const FinalState& fs = apply<FinalState>(event, "FS");
       map<long,int> nCount;
       int ntotal(0);
       Particle outgoing;
       for (const Particle& p :  fs.particles()) {
 	nCount[p.pid()] += 1;
 	if(p.pid()==2212 || p.pid()==2112)
 	  outgoing = p;
 	++ntotal;
       }
       if(ntotal==2) {
 	if(nCount[2212]==1 && nCount[-2212]==1) {
 	  _h_proton->fill(outgoing.momentum().p3().unit().dot(axis));
 	}
 	else if(nCount[2112]==1 && nCount[-2112]==1) {
 	  _h_neutron->fill(outgoing.momentum().p3().unit().dot(axis));
 	}
       }
     }
 
     pair<double,pair<double,double> > calcAlpha(Histo1DPtr hist) {
       if(hist->numEntries()==0.) return make_pair(0.,make_pair(0.,0.));
       double sum1(0.),sum2(0.),sum3(0.),sum4(0.),sum5(0.);
       for (auto bin : hist->bins() ) {
        	double Oi = bin.area();
 	if(Oi==0.) continue;
 	double a =  1.5*(bin.xMax() - bin.xMin());
 	double b = 0.5*(pow(bin.xMax(),3) - pow(bin.xMin(),3));
        	double Ei = bin.areaErr();
 	sum1 +=   a*Oi/sqr(Ei);
 	sum2 +=   b*Oi/sqr(Ei);
 	sum3 += sqr(a)/sqr(Ei);
 	sum4 += sqr(b)/sqr(Ei);
 	sum5 +=    a*b/sqr(Ei);
       }
       // calculate alpha
       double alpha = (-3*sum1 + 9*sum2 + sum3 - 3*sum5)/(sum1 - 3*sum2 + 3*sum4 - sum5);
       // and error
       double cc = -pow((sum3 + 9*sum4 - 6*sum5),3);
       double bb = -2*sqr(sum3 + 9*sum4 - 6*sum5)*(sum1 - 3*sum2 + 3*sum4 - sum5);
       double aa =  sqr(sum1 - 3*sum2 + 3*sum4 - sum5)*(-sum3 - 9*sum4 + sqr(sum1 - 3*sum2 + 3*sum4 - sum5) + 6*sum5);      
       double dis = sqr(bb)-4.*aa*cc;
       if(dis>0.) {
 	dis = sqrt(dis);
 	return make_pair(alpha,make_pair(0.5*(-bb+dis)/aa,-0.5*(-bb-dis)/aa));
       }
       else {
 	return make_pair(alpha,make_pair(0.,0.));
       }
     }
 
     /// Normalise histograms etc., after the run
     void finalize() {
       // proton
       normalize(_h_proton );
       pair<double,pair<double,double> > alpha = calcAlpha(_h_proton);
       Scatter2DPtr _h_alpha_proton;
       book(_h_alpha_proton,1,1,1);
       _h_alpha_proton->addPoint(0.5, alpha.first, make_pair(0.5,0.5),
 				make_pair(alpha.second.first,alpha.second.second) );
       // neutron
       normalize(_h_neutron);
       alpha = calcAlpha(_h_neutron);
       Scatter2DPtr _h_alpha_neutron;
       book(_h_alpha_neutron, 1,1,2);
       _h_alpha_neutron->addPoint(0.5, alpha.first, make_pair(0.5,0.5),
 				 make_pair(alpha.second.first,alpha.second.second) );
     }
 
     //@}
 
 
     /// @name Histograms
     //@{
     Histo1DPtr _h_proton,_h_neutron;
     //@}
 
 
   };
 
 
   // The hook for the plugin system
   DECLARE_RIVET_PLUGIN(BESIII_2012_I1113599);
 
 
 }