Rivet analyses
Cross section for e+e− → K+K−π0π0 from 2.000 to 2.644 GeV
Experiment: BESIII (BEPC)
Inspire ID: 1775344
Status: VALIDATED
Authors: - Peter Richardson
References: - Phys.Rev.Lett. 124 (2020) 112001
Beams: e+ e-
Beam energies: (1.0, 1.0); (1.1, 1.1); (1.1, 1.1); (1.1, 1.1); (1.1, 1.1); (1.1, 1.1); (1.2, 1.2); (1.2, 1.2); (1.2, 1.2); (1.3, 1.3)GeV
Run details: - e+e- to hadrons.
Cross section for e+e− → K+K−π0π0 for centre-of-mass energies from 2.000 to 2.644 GeV measured by BES. The Born cross sections for the subprocesses e+e− → ϕπ0π0, K(1460)+K−, K1(1400)+K−, K1(1270)+K− and K*(892)+K*(892)− are also measured. In addition kinematic distributions are measured at the centre-of-mass energies with the highest integrated luminosity, i.e. 2.125 and 2.396 GeV.
Source
code:BESIII_2020_I1775344.cc
// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/UnstableParticles.hh"
namespace Rivet {
/// @brief e+e- > K+K- pi0pi0
class BESIII_2020_I1775344 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2020_I1775344);
/// @name Analysis methods
/// @{
/// Book histograms and initialise projections before the run
void init() {
// Initialise and register projections
declare(FinalState(), "FS");
declare(UnstableParticles(), "UFS");
// histograms
for (double eVal : allowedEnergies()) {
const string en = toString(round(eVal / MeV));
if (isCompatibleWithSqrtS(eVal)) _sqs = en;
if (en == "2125"s) {
book(_h[en + "KK"], 7, 1, 1);
book(_h[en + "pipi"], 7, 1, 2);
book(_h[en + "Kpi"], 7, 1, 3);
book(_h[en + "KKpi"], 7, 1, 4);
book(_h[en + "Kpipi"], 7, 1, 5);
}
else if (en == "2396"s) {
book(_h[en + "KK"], 8, 1, 1);
book(_h[en + "pipi"], 8, 1, 2);
book(_h[en + "Kpi"], 8, 1, 3);
book(_h[en + "KKpi"], 8, 1, 4);
book(_h[en + "Kpipi"], 8, 1, 5);
}
}
raiseBeamErrorIf(_sqs.empty());
for (size_t ix = 0; ix < 6; ++ix) {
book(_c[ix], 1 + ix, 1, 1);
}
for (const string& en : _c[0].binning().edges<0>()) {
const double eval = stod(en);
if (isCompatibleWithSqrtS(eval)) {
_edge = en;
break;
}
}
}
void findChildren(const Particle& p, map<long, int>& nRes, int& ncount) const {
for (const Particle& child : p.children()) {
if (child.children().empty()) {
nRes[child.pid()] -= 1;
--ncount;
}
else {
findChildren(child, nRes, ncount);
}
}
}
/// Perform the per-event analysis
void analyze(const Event& event) {
const FinalState& fs = apply<FinalState>(event, "FS");
// find the final-state particles
map<long, int> nCount;
int ntotal(0);
Particles Kp, pi0;
for (const Particle& p : fs.particles()) {
nCount[p.pid()] += 1;
++ntotal;
if (p.abspid() == 321)
Kp += p;
else if (p.pid() == 111)
pi0 += p;
}
// intermediates
const FinalState& ufs = apply<FinalState>(event, "UFS");
for (const Particle& p :
ufs.particles(Cuts::abspid == 100321 or Cuts::abspid == 10323 or Cuts::abspid == 20323
or Cuts::pid == 333 or Cuts::abspid == 323)) {
if (p.children().empty()) continue;
map<long, int> nRes = nCount;
int ncount = ntotal;
findChildren(p, nRes, ncount);
// X-/+ with K+/-
if ((p.abspid() == 100321 || p.abspid() == 10323 || p.abspid() == 20323) && ncount == 1) {
bool matched = true;
int Kid = -p.pid() / p.abspid() * 321;
for (const auto& val : nRes) {
if (val.first == Kid) {
if (val.second != 1) {
matched = false;
break;
}
}
else if (val.second != 0) {
matched = false;
break;
}
}
if (matched) {
if (p.abspid() == 100321)
_c[2]->fill(_edge);
else if (p.abspid() == 20323)
_c[3]->fill(_edge);
else if (p.abspid() == 10323)
_c[4]->fill(_edge);
}
}
else if (p.pid() == 333 && ncount == 2) { // phi + 2pi0
bool matched = true;
for (const auto& val : nRes) {
if (val.first == 111) {
if (val.second != 2) {
matched = false;
break;
}
}
else if (val.second != 0) {
matched = false;
break;
}
}
if (matched) _c[1]->fill(_edge);
}
else if (p.abspid() == 323) { // K*K*
for (const Particle& p2 : ufs.particles(Cuts::pid == -p.pid())) {
map<long, int> nResB = nRes;
int ncountB = ncount;
findChildren(p2, nResB, ncountB);
if (ncountB != 0) continue;
bool matched = true;
for (const auto& val : nResB) {
if (val.second != 0) {
matched = false;
break;
}
}
if (matched) _c[5]->fill(_edge);
}
}
}
// final-state
if (ntotal == 4 && nCount[321] == 1 && nCount[-321] == 1 && nCount[111] == 2) {
_c[0]->fill(_edge);
if (_sqs == "2125"s || _sqs == "2396"s) {
FourMomentum pKK = Kp[0].mom() + Kp[1].mom();
_h[_sqs + "KK"]->fill(pKK.mass());
FourMomentum pPi = pi0[0].mom() + pi0[1].mom();
_h[_sqs + "pipi"]->fill(pPi.mass());
for (size_t ix = 0; ix < 2; ++ix) {
_h[_sqs + "KKpi"]->fill((pKK + pi0[ix].mom()).mass());
_h[_sqs + "Kpipi"]->fill((pPi + Kp[ix].mom()).mass());
for (size_t iy = 0; iy < 2; ++iy) {
_h[_sqs + "Kpi"]->fill((Kp[ix].mom() + pi0[iy].mom()).mass());
}
}
}
}
}
/// Normalise histograms etc., after the run
void finalize() {
scale(_c, crossSection() / sumOfWeights() / nanobarn);
normalize(_h);
}
/// @}
/// @name Histograms
/// @{
BinnedHistoPtr<string> _c[6];
map<string, Histo1DPtr> _h;
string _sqs = "", _edge = "";
/// @}
};
RIVET_DECLARE_PLUGIN(BESIII_2020_I1775344);
}