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Rivet analyses reference
BELLE_2007_I723916
Decay angles for $\Lambda_c(2880)^+\to\Sigma_c^{0,++}\pi^{+,-}$
Experiment: BELLE (KEKB)
Inspire ID: 723916
Status: VALIDATED NOHEPDATA
Authors:
References:
- Phys.Rev.Lett. 98 (2007) 262001
Beams: e+ e-
Beam energies: (5.3, 5.3) GeV
Run details:
Measurement of the helicity and decay angles for the decay $\Lambda_c(2880)^+\to\Sigma_c^{0,++}\pi^{+,-}$. The PDG code for this particle is not specified and which multiplet it belongs to is unclear. The default is to use, 4126, i.e the first spin $\frac{5}{2}$ state
Source code:
BELLE_2007_I723916.cc
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101 | // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/Beam.hh"
#include "Rivet/Projections/UnstableParticles.hh"
namespace Rivet {
/// @brief Lambda_c(2880) -> Sigma_c pi
class BELLE_2007_I723916 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2007_I723916);
/// @name Analysis methods
/// @{
/// Book histograms and initialise projections before the run
void init() {
declare(Beam(), "Beams");
// set the PDG code
_pid = getOption<double>("PID", 4126);
// projections
declare(UnstableParticles(Cuts::abspid==_pid), "UFS");
for(unsigned int ix=0;ix<2;++ix)
book(_h[ix],1,1,1+ix);
}
/// 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();
// Get beams and average beam momentum
const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
for (const Particle& p : ufs.particles()) {
// xp cut
double xp = p.momentum().p3().mod()/sqrt(0.25*sqrtS()-p.mass2());
if (xp<.7) continue;
// find the decay products
int sign = p.pid()/p.abspid();
// first decay
if(p.children().size()!=2) continue;
Particle Sigma,pi1;
if((p.children()[0].abspid()== 4222*sign &&
p.children()[1].abspid()==-211 *sign) ||
(p.children()[0].abspid()== 4112*sign &&
p.children()[1].abspid()== 211 *sign) ) {
Sigma = p.children()[0];
pi1 = p.children()[1];
}
else if((p.children()[1].abspid()== 4222*sign &&
p.children()[0].abspid()==-211 *sign) ||
(p.children()[1].abspid()== 4112*sign &&
p.children()[0].abspid()== 211 *sign) ) {
Sigma = p.children()[1];
pi1 = p.children()[0];
}
else
continue;
Vector3 axis1 = p.momentum().p3().unit();
LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(p.momentum().betaVec());
Vector3 axis2 = boost.transform(pi1.momentum()).p3().unit();
_h[0]->fill(axis1.dot(axis2));
Vector3 axis3 = axis.cross(axis1).unit();
Vector3 axis4 = axis1.cross(axis2).unit();
double phi = acos(axis3.dot(axis4));
_h[1]->fill(phi);
}
}
/// Normalise histograms etc., after the run
void finalize() {
for(unsigned int ix=0;ix<2;++ix)
normalize(_h[ix]);
}
/// @}
/// @name Histograms
/// @{
int _pid;
Histo1DPtr _h[2];
/// @}
};
RIVET_DECLARE_PLUGIN(BELLE_2007_I723916);
}
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