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Rivet analyses reference
BELLE_2021_I1809180
Helicity and decay angles for the decay $\Xi_c(2790)^+\to\Xi_c^{*0}(\to\Xi_c^+\pi^-)\pi^+$'
Experiment: BELLE (KEKB)
Inspire ID: 1809180
Status: VALIDATED NOHEPDATA
Authors:
References:
- Phys.Rev.D 103 (2021) 11, L111101
Beams: e+ e-
Beam energies: (5.3, 5.3) GeV
Run details:
Measurement of the helicity and decay angles for the decay $\Xi_c(2790)^+\to\Xi_c^{*0}(\to\Xi_c^+\pi^-)\pi^+$. The PDG code for this particle is not specified and which multiplet it belongs to is unclear. The default is to use 204232, i.e. it is in the same multiplet as the Roper resonance, but this can be changed using the PID option.
Source code:
BELLE_2021_I1809180.cc
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101 | // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
namespace Rivet {
/// @brief Xi_c(2970) decays
class BELLE_2021_I1809180 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2021_I1809180);
/// @name Analysis methods
/// @{
/// Book histograms and initialise projections before the run
void init() {
// set the PDG code
_pid = getOption<double>("PID", 204232);
// projections
declare(UnstableParticles(Cuts::abspid==_pid), "UFS");
for(unsigned int ix=0;ix<2;++ix)
book(_h[ix],1+ix,1,1);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
// 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
// first decay
if(p.children().size()!=2) continue;
Particle XiStar,pi1;
if(p.children()[0].abspid()==4314 &&
p.children()[1].abspid()== 211) {
XiStar = p.children()[0];
pi1 = p.children()[1];
}
else if(p.children()[1].abspid()==4314 &&
p.children()[0].abspid()== 211) {
XiStar = p.children()[1];
pi1 = p.children()[0];
}
else
continue;
Vector3 axis1 = p.momentum().p3().unit();
LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(p.momentum().betaVec());
FourMomentum ppi1 = boost.transform(pi1.momentum());
_h[0]->fill(axis1.dot(ppi1.p3().unit()));
Particle pi2;
// second decay
if(XiStar.children()[0].abspid()==4232 &&
XiStar.children()[1].abspid()== 211) {
pi2 = XiStar.children()[1];
}
else if(XiStar.children()[1].abspid()== 4232 &&
XiStar.children()[0].abspid()== 211) {
pi2 = XiStar.children()[0];
}
else
continue;
FourMomentum pXiStar = boost.transform(XiStar.momentum());
FourMomentum ppi2 = boost.transform(pi2.momentum());
LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pXiStar.betaVec());
ThreeVector axis2 = pXiStar.p3().unit();
ppi2 = boost2.transform(ppi2);
_h[1]->fill(axis2.dot(ppi2.p3().unit()));
}
}
/// 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_2021_I1809180);
}
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