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Analysis.cc
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// Analysis.cc is a part of the PYTHIA event generator.
// Copyright (C) 2024 Torbjorn Sjostrand.
// PYTHIA is licenced under the GNU GPL v2 or later, see COPYING for details.
// Please respect the MCnet Guidelines, see GUIDELINES for details.
// Function definitions (not found in the header) for the
// Sphericity, Thrust, ClusJet, CellJet and SlowJet classes.
#include "Pythia8/Analysis.h"
#include "Pythia8/FJcore.h"
namespace Pythia8 {
//==========================================================================
// Sphericity class.
// This class finds sphericity-related properties of an event.
//--------------------------------------------------------------------------
// Constants: could be changed here if desired, but normally should not.
// These are of technical nature, as described for each.
// Minimum number of particles to perform study.
const int Sphericity::NSTUDYMIN = 2;
// Maximum number of times that an error warning will be printed.
const int Sphericity::TIMESTOPRINT = 1;
// Assign mimimum squared momentum in weight to avoid division by zero.
const double Sphericity::P2MIN = 1e-20;
// Second eigenvalue not too low or not possible to find eigenvectors.
const double Sphericity::EIGENVALUEMIN = 1e-10;
//--------------------------------------------------------------------------
// Analyze event.
bool Sphericity::analyze(const Event& event) {
// Initial values, tensor and counters zero.
eVal1 = eVal2 = eVal3 = 0.;
eVec1 = eVec2 = eVec3 = 0.;
double tt[4][4];
for (int j = 1; j < 4; ++j)
for (int k = j; k < 4; ++k) tt[j][k] = 0.;
int nStudy = 0;
double denom = 0.;
// Loop over desired particles in the event.
for (int i = 0; i < event.size(); ++i)
if (event[i].isFinal()) {
if (select > 2 && event[i].isNeutral() ) continue;
if (select == 2 && !event[i].isVisible() ) continue;
++nStudy;
// Calculate matrix to be diagonalized. Special cases for speed.
double pNow[4];
pNow[1] = event[i].px();
pNow[2] = event[i].py();
pNow[3] = event[i].pz();
double p2Now = pNow[1]*pNow[1] + pNow[2]*pNow[2] + pNow[3]*pNow[3];
double pWeight = 1.;
if (powerInt == 1) pWeight = 1. / sqrt(max(P2MIN, p2Now));
else if (powerInt == 0) pWeight = pow( max(P2MIN, p2Now), powerMod);
for (int j = 1; j < 4; ++j)
for (int k = j; k < 4; ++k) tt[j][k] += pWeight * pNow[j] * pNow[k];
denom += pWeight * p2Now;
}
// Very low multiplicities (0 or 1) not considered.
if (nStudy < NSTUDYMIN) {
if (nFew < TIMESTOPRINT) cout << " PYTHIA Error in "
<< "Sphericity::analyze: too few particles" << endl;
++nFew;
return false;
}
// Normalize tensor to trace = 1.
for (int j = 1; j < 4; ++j)
for (int k = j; k < 4; ++k) tt[j][k] /= denom;
// Find eigenvalues to matrix (third degree equation).
double qCoef = ( tt[1][1] * tt[2][2] + tt[1][1] * tt[3][3]
+ tt[2][2] * tt[3][3] - pow2(tt[1][2]) - pow2(tt[1][3])
- pow2(tt[2][3]) ) / 3. - 1./9.;
double qCoefRt = sqrt( -qCoef);
double rCoef = -0.5 * ( qCoef + 1./9. + tt[1][1] * pow2(tt[2][3])
+ tt[2][2] * pow2(tt[1][3]) + tt[3][3] * pow2(tt[1][2])
- tt[1][1] * tt[2][2] * tt[3][3] )
+ tt[1][2] * tt[1][3] * tt[2][3] + 1./27.;
double pTemp = max( min( rCoef / pow3(qCoefRt), 1.), -1.);
double pCoef = cos( acos(pTemp) / 3.);
double pCoefRt = sqrt( 3. * (1. - pow2(pCoef)) );
eVal1 = 1./3. + qCoefRt * max( 2. * pCoef, pCoefRt - pCoef);
eVal3 = 1./3. + qCoefRt * min( 2. * pCoef, -pCoefRt - pCoef);
eVal2 = 1. - eVal1 - eVal3;
// Begin find first and last eigenvector.
for (int iVal = 0; iVal < 2; ++iVal) {
double eVal = (iVal == 0) ? eVal1 : eVal3;
// If all particles are back-to-back then simpleminded third axis.
if (iVal > 0 && eVal2 < EIGENVALUEMIN) {
if ( abs(eVec1.pz()) > 0.5) eVec3 = Vec4( 1., 0., 0., 0.);
else eVec3 = Vec4( 0., 0., 1., 0.);
eVec3 -= dot3( eVec1, eVec3) * eVec1;
eVec3 /= eVec3.pAbs();
eVec2 = cross3( eVec1, eVec3);
return true;
}
// Set up matrix to diagonalize.
double dd[4][4];
for (int j = 1; j < 4; ++j) {
dd[j][j] = tt[j][j] - eVal;
for (int k = j + 1; k < 4; ++k) {
dd[j][k] = tt[j][k];
dd[k][j] = tt[j][k];
}
}
// Find largest = pivotal element in matrix.
int jMax = 0;
int kMax = 0;
double ddMax = 0.;
for (int j = 1; j < 4; ++j)
for (int k = 1; k < 4; ++k)
if (abs(dd[j][k]) > ddMax) {
jMax = j;
kMax = k;
ddMax = abs(dd[j][k]);
}
// Subtract one row from the other two; find new largest element.
int jMax2 = 0;
ddMax = 0.;
for (int j = 1; j < 4; ++j)
if ( j != jMax) {
double pivot = dd[j][kMax] / dd[jMax][kMax];
for (int k = 1; k < 4; ++k) {
dd[j][k] -= pivot * dd[jMax][k];
if (abs(dd[j][k]) > ddMax) {
jMax2 = j;
ddMax = abs(dd[j][k]);
}
}
}
// Construct eigenvector. Normalize to unit length; sign irrelevant.
int k1 = kMax + 1; if (k1 > 3) k1 -= 3;
int k2 = kMax + 2; if (k2 > 3) k2 -= 3;
double eVec[4];
eVec[k1] = -dd[jMax2][k2];
eVec[k2] = dd[jMax2][k1];
eVec[kMax] = (dd[jMax][k1] * dd[jMax2][k2]
- dd[jMax][k2] * dd[jMax2][k1]) / dd[jMax][kMax];
double length = sqrt( pow2(eVec[1]) + pow2(eVec[2])
+ pow2(eVec[3]) );
// Store eigenvectors.
if (iVal == 0) eVec1 = Vec4( eVec[1] / length,
eVec[2] / length, eVec[3] / length, 0.);
else eVec3 = Vec4( eVec[1] / length,
eVec[2] / length, eVec[3] / length, 0.);
}
// Middle eigenvector is orthogonal to the other two; sign irrelevant.
eVec2 = cross3( eVec1, eVec3);
// Done.
return true;
}
//--------------------------------------------------------------------------
// Provide a listing of the info.
void Sphericity::list() const {
// Header.
cout << "\n -------- PYTHIA Sphericity Listing -------- \n";
if (powerInt !=2) cout<< " Nonstandard momentum power = "
<< fixed << setprecision(3) << setw(6) << power << "\n";
cout << "\n no lambda e_x e_y e_z \n";
// The three eigenvalues and eigenvectors.
cout << setprecision(5);
cout << " 1" << setw(11) << eVal1 << setw(11) << eVec1.px()
<< setw(10) << eVec1.py() << setw(10) << eVec1.pz() << "\n";
cout << " 2" << setw(11) << eVal2 << setw(11) << eVec2.px()
<< setw(10) << eVec2.py() << setw(10) << eVec2.pz() << "\n";
cout << " 3" << setw(11) << eVal3 << setw(11) << eVec3.px()
<< setw(10) << eVec3.py() << setw(10) << eVec3.pz() << "\n";
// Listing finished.
cout << "\n -------- End PYTHIA Sphericity Listing ----" << endl;
}
//==========================================================================
// Thrust class.
// This class finds thrust-related properties of an event.
//--------------------------------------------------------------------------
// Constants: could be changed here if desired, but normally should not.
// These are of technical nature, as described for each.
// Minimum number of particles to perform study.
const int Thrust::NSTUDYMIN = 2;
// Maximum number of times that an error warning will be printed.
const int Thrust::TIMESTOPRINT = 1;
// Cross product not too low to avoid division by zero.
const double Thrust::CROSSMIN = 1e-10;
// Major not too low or not possible to find major axis.
const double Thrust::MAJORMIN = 1e-10;
//--------------------------------------------------------------------------
// Analyze event.
bool Thrust::analyze(const Event& event) {
// Initial values and counters zero.
eVal1 = eVal2 = eVal3 = 0.;
eVec1 = eVec2 = eVec3 = 0.;
int nStudy = 0;
vector<Vec4> pOrder;
Vec4 pSum, nRef, pPart, pFull, pMax;
// Loop over desired particles in the event.
for (int i = 0; i < event.size(); ++i)
if (event[i].isFinal()) {
if (select > 2 && event[i].isNeutral() ) continue;
if (select == 2 && !event[i].isVisible() ) continue;
++nStudy;
// Store momenta. Use energy component for absolute momentum.
Vec4 pNow = event[i].p();
pNow.e(pNow.pAbs());
pSum += pNow;
pOrder.push_back(pNow);
}
// Very low multiplicities (0 or 1) not considered.
if (nStudy < NSTUDYMIN) {
if (nFew < TIMESTOPRINT) cout << " PYTHIA Error in "
<< "Thrust::analyze: too few particles" << endl;
++nFew;
return false;
}
// Try all combinations of reference vector orthogonal to two particles.
for (int i1 = 0; i1 < nStudy - 1; ++i1)
for (int i2 = i1 + 1; i2 < nStudy; ++i2) {
nRef = cross3( pOrder[i1], pOrder[i2]);
nRef /= max( CROSSMIN, nRef.pAbs());
pPart = 0.;
// Add all momenta with sign; two choices for each reference particle.
for (int i = 0; i < nStudy; ++i) if (i != i1 && i != i2) {
if (dot3(pOrder[i], nRef) > 0.) pPart += pOrder[i];
else pPart -= pOrder[i];
}
for (int j = 0; j < 4; ++j) {
if (j == 0) pFull = pPart + pOrder[i1] + pOrder[i2];
else if (j == 1) pFull = pPart + pOrder[i1] - pOrder[i2];
else if (j == 2) pFull = pPart - pOrder[i1] + pOrder[i2];
else pFull = pPart - pOrder[i1] - pOrder[i2];
pFull.e(pFull.pAbs());
if (pFull.e() > pMax.e()) pMax = pFull;
}
}
// Maximum gives thrust axis and value.
eVal1 = pMax.e() / pSum.e();
eVec1 = pMax / pMax.e();
eVec1.e(0.);
// Subtract momentum along thrust axis.
double pAbsSum = 0.;
for (int i = 0; i < nStudy; ++i) {
pOrder[i] -= dot3( eVec1, pOrder[i]) * eVec1;
pOrder[i].e(pOrder[i].pAbs());
pAbsSum += pOrder[i].e();
}
// Simpleminded major and minor axes if too little transverse left.
if (pAbsSum < MAJORMIN * pSum.e()) {
if ( abs(eVec1.pz()) > 0.5) eVec2 = Vec4( 1., 0., 0., 0.);
else eVec2 = Vec4( 0., 0., 1., 0.);
eVec2 -= dot3( eVec1, eVec2) * eVec1;
eVec2 /= eVec2.pAbs();
eVec3 = cross3( eVec1, eVec2);
return true;
}
// Try all reference vectors orthogonal to one particles.
pMax = 0.;
for (int i1 = 0; i1 < nStudy; ++i1) {
nRef = cross3( pOrder[i1], eVec1);
nRef /= max(CROSSMIN, nRef.pAbs());
pPart = 0.;
// Add all momenta with sign; two choices for each reference particle.
for (int i = 0; i < nStudy; ++i) if (i != i1) {
if (dot3(pOrder[i], nRef) > 0.) pPart += pOrder[i];
else pPart -= pOrder[i];
}
pFull = pPart + pOrder[i1];
pFull.e(pFull.pAbs());
if (pFull.e() > pMax.e()) pMax = pFull;
pFull = pPart - pOrder[i1];
pFull.e(pFull.pAbs());
if (pFull.e() > pMax.e()) pMax = pFull;
}
// Maximum gives major axis and value.
eVal2 = pMax.e() / pSum.e();
eVec2 = pMax / pMax.e();
eVec2.e(0.);
// Orthogonal direction gives minor axis, and from there value.
eVec3 = cross3( eVec1, eVec2);
pAbsSum = 0.;
for (int i = 0; i < nStudy; ++i)
pAbsSum += abs( dot3(eVec3, pOrder[i]) );
eVal3 = pAbsSum / pSum.e();
// Done.
return true;
}
//--------------------------------------------------------------------------
// Provide a listing of the info.
void Thrust::list() const {
// Header.
cout << "\n -------- PYTHIA Thrust Listing ------------ \n"
<< "\n value e_x e_y e_z \n";
// The thrust, major and minor values and related event axes.
cout << setprecision(5);
cout << " Thr" << setw(11) << eVal1 << setw(11) << eVec1.px()
<< setw(10) << eVec1.py() << setw(10) << eVec1.pz() << "\n";
cout << " Maj" << setw(11) << eVal2 << setw(11) << eVec2.px()
<< setw(10) << eVec2.py() << setw(10) << eVec2.pz() << "\n";
cout << " Min" << setw(11) << eVal3 << setw(11) << eVec3.px()
<< setw(10) << eVec3.py() << setw(10) << eVec3.pz() << "\n";
// Listing finished.
cout << "\n -------- End PYTHIA Thrust Listing --------" << endl;
}
//==========================================================================
// SingleClusterJet class.
// Simple helper class to ClusterJet for a jet and its contents.
//--------------------------------------------------------------------------
// Constants: could be changed here if desired, but normally should not.
// These are of technical nature, as described for each.
// Assign minimal pAbs to avoid division by zero.
const double SingleClusterJet::PABSMIN = 1e-10;
//--------------------------------------------------------------------------
// Distance measures between two SingleClusterJet objects.
double dist2Fun(int measure, const SingleClusterJet& j1,
const SingleClusterJet& j2) {
// JADE distance.
if (measure == 2) return 2. * j1.pJet.e() * j2.pJet.e()
* (1. - dot3( j1.pJet, j2.pJet) / (j1.pAbs * j2.pAbs) );
// Durham distance.
if (measure == 3) return 2. * pow2( min( j1.pJet.e(), j2.pJet.e() ) )
* (1. - dot3( j1.pJet, j2.pJet) / (j1.pAbs * j2.pAbs) );
// Lund distance; "default".
return (j1.pAbs * j2.pAbs - dot3( j1.pJet, j2.pJet))
* 2. * j1.pAbs * j2.pAbs / pow2(j1.pAbs + j2.pAbs);
}
//==========================================================================
// ClusterJet class.
// This class performs a jet clustering according to different
// distance measures: Lund, JADE or Durham.
//--------------------------------------------------------------------------
// Constants: could be changed here if desired, but normally should not.
// These are of technical nature, as described for each.
// Maximum number of times that an error warning will be printed.
const int ClusterJet::TIMESTOPRINT = 1;
// Assume the pi+- mass for all particles, except the photon, in one option.
const double ClusterJet::PIMASS = 0.13957;
// Assign minimal pAbs to avoid division by zero.
const double ClusterJet::PABSMIN = 1e-10;
// Initial pT/m preclustering scale as fraction of clustering one.
const double ClusterJet::PRECLUSTERFRAC = 0.1;
// Step with which pT/m is reduced if preclustering gives too few jets.
const double ClusterJet::PRECLUSTERSTEP = 0.8;
//--------------------------------------------------------------------------
// Analyze event.
bool ClusterJet::analyze(const Event& event, double yScaleIn,
double pTscaleIn, int nJetMinIn, int nJetMaxIn) {
// Input values. Initial values zero.
yScale = yScaleIn;
pTscale = pTscaleIn;
nJetMin = nJetMinIn;
nJetMax = nJetMaxIn;
particles.resize(0);
jets.resize(0);
Vec4 pSum;
distances.clear();
// Loop over desired particles in the event.
for (int i = 0; i < event.size(); ++i)
if (event[i].isFinal()) {
if (select > 2 && event[i].isNeutral() ) continue;
if (select == 2 && !event[i].isVisible() ) continue;
// Store them, possibly with modified mass => new energy.
Vec4 pTemp = event[i].p();
if (massSet == 0 || massSet == 1) {
double mTemp = (massSet == 0 || event[i].id() == 22)
? 0. : PIMASS;
double eTemp = sqrt(pTemp.pAbs2() + pow2(mTemp));
pTemp.e(eTemp);
}
particles.push_back( SingleClusterJet(pTemp, i) );
pSum += pTemp;
}
// Very low multiplicities not considered.
nParticles = particles.size();
if (nParticles < nJetMin) {
if (nFew < TIMESTOPRINT) cout << " PYTHIA Error in "
<< "ClusterJet::analyze: too few particles" << endl;
++nFew;
return false;
}
// Squared maximum distance in GeV^2 for joining.
double p2Sum = pSum.m2Calc();
dist2Join = max( yScale * p2Sum, pow2(pTscale));
dist2BigMin = 2. * max( dist2Join, p2Sum);
// Do preclustering if desired and possible.
if (doPrecluster && nParticles > nJetMin + 2) {
precluster();
if (doReassign) reassign();
}
// If no preclustering: each particle is a starting jet.
else for (int i = 0; i < nParticles; ++i) {
jets.push_back( SingleClusterJet(particles[i]) );
particles[i].daughter = i;
}
// Begin iteration towards fewer jets.
for ( ; ; ) {
// Find the two closest jets.
double dist2Min = dist2BigMin;
int jMin = 0;
int kMin = 0;
for (int j = 0; j < int(jets.size()) - 1; ++j)
for (int k = j + 1; k < int(jets.size()); ++k) {
double dist2 = dist2Fun( measure, jets[j], jets[k]);
if (dist2 < dist2Min) {
dist2Min = dist2;
jMin = j;
kMin = k;
}
}
// Stop if no pair below cut and not more jets than allowed.
if ( dist2Min > dist2Join
&& (nJetMax < nJetMin || int(jets.size()) <= nJetMax) ) break;
// Stop if reached minimum allowed number of jets. Else continue.
if (int(jets.size()) <= nJetMin) break;
// Join two closest jets.
jets[jMin].pJet += jets[kMin].pJet;
jets[jMin].pAbs = max( PABSMIN, jets[jMin].pJet.pAbs());
jets[jMin].multiplicity += jets[kMin].multiplicity;
for (int i = 0; i < nParticles; ++i)
if (particles[i].daughter == kMin) particles[i].daughter = jMin;
// Save the last 5 distances.
distances.push_front(dist2Min);
if (distances.size() > 5) distances.pop_back();
// Move up last jet to empty slot to shrink list.
jets[kMin] = jets.back();
jets.pop_back();
int iEnd = jets.size();
for (int i = 0; i < nParticles; ++i)
if (particles[i].daughter == iEnd) particles[i].daughter = kMin;
// Do reassignments of particles to nearest jet if desired.
if (doReassign) reassign();
}
// Order jets in decreasing energy.
for (int j = 0; j < int(jets.size()) - 1; ++j)
for (int k = int(jets.size()) - 1; k > j; --k)
if (jets[k].pJet.e() > jets[k-1].pJet.e()) {
swap( jets[k], jets[k-1]);
for (int i = 0; i < nParticles; ++i) {
if (particles[i].daughter == k) particles[i].daughter = k-1;
else if (particles[i].daughter == k-1) particles[i].daughter = k;
}
}
// Done.
return true;
}
//--------------------------------------------------------------------------
// Precluster nearby particles to save computer time.
void ClusterJet::precluster() {
// Begin iteration over preclustering scale.
distPre = PRECLUSTERFRAC * sqrt(dist2Join) / PRECLUSTERSTEP;
for ( ; ;) {
distPre *= PRECLUSTERSTEP;
dist2Pre = pow2(distPre);
for (int i = 0; i < nParticles; ++i) {
particles[i].daughter = -1;
particles[i].isAssigned = false;
}
// Sum up low-momentum region. Jet if enough momentum.
Vec4 pCentral;
int multCentral = 0;
for (int i = 0; i < nParticles; ++i)
if (particles[i].pAbs < 2. * distPre) {
pCentral += particles[i].pJet;
multCentral += particles[i].multiplicity;
particles[i].isAssigned = true;
}
if (pCentral.pAbs() > 2. * distPre) {
jets.push_back( SingleClusterJet(pCentral) );
jets.back().multiplicity = multCentral;
for (int i = 0; i < nParticles; ++i)
if (particles[i].isAssigned) particles[i].daughter = 0;
}
// Find fastest remaining particle until none left.
for ( ; ;) {
int iMax = -1;
double pMax = 0.;
for (int i = 0; i < nParticles; ++i)
if ( !particles[i].isAssigned && particles[i].pAbs > pMax) {
iMax = i;
pMax = particles[i].pAbs;
}
if (iMax == -1) break;
// Sum up precluster around it according to distance function.
Vec4 pPre;
int multPre = 0;
int nRemain = 0;
for (int i = 0; i < nParticles; ++i)
if ( !particles[i].isAssigned) {
double dist2 = dist2Fun( measure, particles[iMax],
particles[i]);
if (dist2 < dist2Pre) {
pPre += particles[i].pJet;
++multPre;
particles[i].isAssigned = true;
particles[i].daughter = jets.size();
} else ++nRemain;
}
jets.push_back( SingleClusterJet(pPre) );
jets.back().multiplicity = multPre;
// Decide whether sensible starting configuration or iterate.
if (int(jets.size()) + nRemain < nJetMin) break;
}
if (int(jets.size()) >= nJetMin) break;
}
}
//--------------------------------------------------------------------------
// Reassign particles to nearest jet to correct misclustering.
void ClusterJet::reassign() {
// Reset clustered momenta.
for (int j = 0; j < int(jets.size()); ++j) {
jets[j].pTemp = 0.;
jets[j].multiplicity = 0;
}
// Loop through particles to find closest jet.
for (int i = 0; i < nParticles; ++i) {
particles[i].daughter = -1;
double dist2Min = dist2BigMin;
int jMin = 0;
for (int j = 0; j < int(jets.size()); ++j) {
double dist2 = dist2Fun( measure, particles[i], jets[j]);
if (dist2 < dist2Min) {
dist2Min = dist2;
jMin = j;
}
}
jets[jMin].pTemp += particles[i].pJet;
++jets[jMin].multiplicity;
particles[i].daughter = jMin;
}
// Replace old by new jet momenta.
for (int j = 0; j < int(jets.size()); ++j) {
jets[j].pJet = jets[j].pTemp;
jets[j].pAbs = max( PABSMIN, jets[j].pJet.pAbs());
}
// Check that no empty clusters after reassignments.
for ( ; ; ) {
// If no empty jets then done.
int jEmpty = -1;
for (int j = 0; j < int(jets.size()); ++j)
if (jets[j].multiplicity == 0) jEmpty = j;
if (jEmpty == -1) return;
// Find particle assigned to jet with largest distance to it.
int iSplit = -1;
double dist2Max = 0.;
for (int i = 0; i < nParticles; ++i) {
int j = particles[i].daughter;
double dist2 = dist2Fun( measure, particles[i], jets[j]);
if (dist2 > dist2Max) {
iSplit = i;
dist2Max = dist2;
}
}
// Let this particle form new jet and subtract off from existing.
int jSplit = particles[iSplit].daughter;
jets[jEmpty] = SingleClusterJet( particles[iSplit].pJet );
jets[jSplit].pJet -= particles[iSplit].pJet;
jets[jSplit].pAbs = max( PABSMIN,jets[jSplit].pJet.pAbs());
particles[iSplit].daughter = jEmpty;
--jets[jSplit].multiplicity;
}
}
//--------------------------------------------------------------------------
// Provide a listing of the info.
void ClusterJet::list() const {
// Header.
string method = (measure == 1) ? "Lund pT"
: ( (measure == 2) ? "JADE m" : "Durham kT" ) ;
cout << "\n -------- PYTHIA ClusterJet Listing, " << setw(9) << method
<< " =" << fixed << setprecision(3) << setw(7) << sqrt(dist2Join)
<< " GeV --- \n \n no mult p_x p_y p_z "
<< " e m \n";
// The jets.
for (int i = 0; i < int(jets.size()); ++i) {
cout << setw(4) << i << setw(6) << jets[i].multiplicity << setw(11)
<< jets[i].pJet.px() << setw(11) << jets[i].pJet.py()
<< setw(11) << jets[i].pJet.pz() << setw(11)
<< jets[i].pJet.e() << setw(11) << jets[i].pJet.mCalc()
<< "\n";
}
// Listing finished.
cout << "\n -------- End PYTHIA ClusterJet Listing ---------------"
<< "--------" << endl;
}
//==========================================================================
// CellJet class.
// This class performs a cone jet search in (eta, phi, E_T) space.
//--------------------------------------------------------------------------
// Constants: could be changed here if desired, but normally should not.
// These are of technical nature, as described for each.
// Minimum number of particles to perform study.
const int CellJet::TIMESTOPRINT = 1;
//--------------------------------------------------------------------------
// Analyze event.
bool CellJet::analyze(const Event& event, double eTjetMinIn,
double coneRadiusIn, double eTseedIn) {
// Input values. Initial values zero.
eTjetMin = eTjetMinIn;
coneRadius = coneRadiusIn;
eTseed = eTseedIn;
jets.resize(0);
vector<SingleCell> cells;
// Loop over desired particles in the event.
for (int i = 0; i < event.size(); ++i)
if (event[i].isFinal()) {
if (select > 2 && event[i].isNeutral() ) continue;
if (select == 2 && !event[i].isVisible() ) continue;
// Find particle position in (eta, phi, pT) space.
double etaNow = event[i].eta();
if (abs(etaNow) > etaMax) continue;
double phiNow = event[i].phi();
double pTnow = event[i].pT();
int iEtaNow = max(1, min( nEta, 1 + int(nEta * 0.5
* (1. + etaNow / etaMax) ) ) );
int iPhiNow = max(1, min( nPhi, 1 + int(nPhi * 0.5
* (1. + phiNow / M_PI) ) ) );
int iCell = nPhi * iEtaNow + iPhiNow;
// Add pT to cell already hit or book a new cell.
bool found = false;
for (int j = 0; j < int(cells.size()); ++j) {
if (iCell == cells[j].iCell) {
found = true;
++cells[j].multiplicity;
cells[j].eTcell += pTnow;
continue;
}
}
if (!found) {
double etaCell = (etaMax / nEta) * (2 * iEtaNow - 1 - nEta);
double phiCell = (M_PI / nPhi) * (2 * iPhiNow - 1 - nPhi);
cells.push_back( SingleCell( iCell, etaCell, phiCell, pTnow, 1) );
}
}
// Smear true bin content by calorimeter resolution.
if (smear > 0 && rndmPtr != 0)
for (int j = 0; j < int(cells.size()); ++j) {
double eTeConv = (smear < 2) ? 1. : cosh( cells[j].etaCell );
double eBef = cells[j].eTcell * eTeConv;
double eAft = 0.;
do eAft = eBef + resolution * sqrt(eBef) * rndmPtr->gauss();
while (eAft < 0 || eAft > upperCut * eBef);
cells[j].eTcell = eAft / eTeConv;
}
// Remove cells below threshold for seed or for use at all.
for (int j = 0; j < int(cells.size()); ++j) {
if (cells[j].eTcell < eTseed) cells[j].canBeSeed = false;
if (cells[j].eTcell < threshold) cells[j].isUsed = true;
}
// Find seed cell: the one with highest pT of not yet probed ones.
for ( ; ; ) {
int jMax = 0;
double eTmax = 0.;
for (int j = 0; j < int(cells.size()); ++j)
if (cells[j].canBeSeed && cells[j].eTcell > eTmax) {
jMax = j;
eTmax = cells[j].eTcell;
}
// If too small cell eT then done, else start new trial jet.
if (eTmax < eTseed) break;
double etaCenterNow = cells[jMax].etaCell;
double phiCenterNow = cells[jMax].phiCell;
double eTjetNow = 0.;
// Sum up unused cells within required distance of seed.
for (int j = 0; j < int(cells.size()); ++j) {
if (cells[j].isUsed) continue;
double dEta = abs( cells[j].etaCell - etaCenterNow );
if (dEta > coneRadius) continue;
double dPhi = abs( cells[j].phiCell - phiCenterNow );
if (dPhi > M_PI) dPhi = 2. * M_PI - dPhi;
if (dPhi > coneRadius) continue;
if (pow2(dEta) + pow2(dPhi) > pow2(coneRadius)) continue;
cells[j].isAssigned = true;
eTjetNow += cells[j].eTcell;
}
// Reject cluster below minimum ET.
if (eTjetNow < eTjetMin) {
cells[jMax].canBeSeed = false;
for (int j = 0; j < int(cells.size()); ++j)
cells[j].isAssigned = false;
// Else find new jet properties.
} else {
double etaWeightedNow = 0.;
double phiWeightedNow = 0.;
int multiplicityNow = 0;
Vec4 pMassiveNow;
for (int j = 0; j < int(cells.size()); ++j)
if (cells[j].isAssigned) {
cells[j].canBeSeed = false;
cells[j].isUsed = true;
cells[j].isAssigned = false;
etaWeightedNow += cells[j].eTcell * cells[j].etaCell;
double phiCell = cells[j].phiCell;
if (abs(phiCell - phiCenterNow) > M_PI)
phiCell += (phiCenterNow > 0.) ? 2. * M_PI : -2. * M_PI;
phiWeightedNow += cells[j].eTcell * phiCell;
multiplicityNow += cells[j].multiplicity;
pMassiveNow += cells[j].eTcell * Vec4(
cos(cells[j].phiCell), sin(cells[j].phiCell),
sinh(cells[j].etaCell), cosh(cells[j].etaCell) );
}
etaWeightedNow /= eTjetNow;
phiWeightedNow /= eTjetNow;
// Bookkeep new jet, in decreasing ET order.
jets.push_back( SingleCellJet( eTjetNow, etaCenterNow, phiCenterNow,
etaWeightedNow, phiWeightedNow, multiplicityNow, pMassiveNow) );
for (int i = int(jets.size()) - 1; i > 0; --i) {
if (jets[i-1].eTjet > jets[i].eTjet) break;
swap( jets[i-1], jets[i]);
}
}
}
// Done.
return true;
}
//--------------------------------------------------------------------------
// Provide a listing of the info.
void CellJet::list() const {
// Header.
cout << "\n -------- PYTHIA CellJet Listing, eTjetMin = "
<< fixed << setprecision(3) << setw(8) << eTjetMin
<< ", coneRadius = " << setw(5) << coneRadius
<< " ------------------------------ \n \n no "
<< " eTjet etaCtr phiCtr etaWt phiWt mult p_x"
<< " p_y p_z e m \n";
// The jets.
for (int i = 0; i < int(jets.size()); ++i) {
cout << setw(4) << i << setw(10) << jets[i].eTjet << setw(8)
<< jets[i].etaCenter << setw(8) << jets[i].phiCenter << setw(8)
<< jets[i].etaWeighted << setw(8) << jets[i].phiWeighted
<< setw(5) << jets[i].multiplicity << setw(11)
<< jets[i].pMassive.px() << setw(11) << jets[i].pMassive.py()
<< setw(11) << jets[i].pMassive.pz() << setw(11)
<< jets[i].pMassive.e() << setw(11)
<< jets[i].pMassive.mCalc() << "\n";
}
// Listing finished.
cout << "\n -------- End PYTHIA CellJet Listing ------------------"
<< "-------------------------------------------------"
<< endl;
}
//==========================================================================
// SlowJet class.
// This class performs clustering in (y, phi, pT) space.
//--------------------------------------------------------------------------
// Constants: could be changed here if desired, but normally should not.
// These are of technical nature, as described for each.
// Minimum number of particles to perform study.
const int SlowJet::TIMESTOPRINT = 1;
// Assume the pi+- mass for all particles, except the photon, in one option.
const double SlowJet::PIMASS = 0.13957;
// Small number to avoid division by zero.
const double SlowJet::TINY = 1e-20;
//--------------------------------------------------------------------------
// Set up list of particles to analyze, and initial distances.
bool SlowJet::setup(const Event& event) {
// Initial values zero.
clusters.resize(0);
jets.resize(0);
jtSize = 0;
// Loop over final particles in the event.
Vec4 pTemp;
double mTemp, pT2Temp, mTTemp, yTemp, phiTemp;
for (int i = 0; i < event.size(); ++i)
if (event[i].isFinal()) {
// Always apply selection options for visible or charged particles.
if (chargedOnly && event[i].isNeutral() ) continue;
else if (visibleOnly && !event[i].isVisible() ) continue;
// Normally use built-in selection machinery.
if (noHook) {
// Pseudorapidity cut to describe detector range.
if (cutInEta && abs(event[i].eta()) > etaMax) continue;
// Optionally modify mass and energy.
pTemp = event[i].p();
mTemp = event[i].m();
if (modifyMass) {
mTemp = (massSet == 0 || event[i].id() == 22) ? 0. : PIMASS;
pTemp.e( sqrt(pTemp.pAbs2() + mTemp*mTemp) );
}
// Alternatively pass info to SlowJetHook for decision.
// User can also modify pTemp and mTemp.
} else {
pTemp = event[i].p();
mTemp = event[i].m();
if ( !sjHookPtr->include( i, event, pTemp, mTemp) ) continue;
}
// Store particle momentum, including some derived quantities.
pT2Temp = max( TINY*TINY, pTemp.pT2());
mTTemp = sqrt( mTemp*mTemp + pT2Temp);
yTemp = (pTemp.pz() > 0)
? log( max( TINY, pTemp.e() + pTemp.pz() ) / mTTemp )
: log( mTTemp / max( TINY, pTemp.e() - pTemp.pz() ) );
phiTemp = pTemp.phi();
clusters.push_back( SingleSlowJet(pTemp, pT2Temp, yTemp, phiTemp, i) );
}
origSize = clusters.size();
// Done here for FJcore machinery.
if (useFJcore) return true;
// Resize arrays to store distances between clusters.
clSize = origSize;
clLast = clSize - 1;
diB.resize(clSize);
dij.resize(clSize * (clSize - 1) / 2);
// Loop through particles and find distance to beams.
for (int i = 0; i < clSize; ++i) {
if (isAnti) diB[i] = 1. / clusters[i].pT2;
else if (isKT) diB[i] = clusters[i].pT2;
else diB[i] = 1.;
// Loop through pairs and find relative distance.
for (int j = 0; j < i; ++j) {
dPhi = abs( clusters[i].phi - clusters[j].phi );
if (dPhi > M_PI) dPhi = 2. * M_PI - dPhi;
dijTemp = (useStandardR)
? (pow2( clusters[i].y - clusters[j].y) + dPhi*dPhi) / R2
: 2. * (cosh( clusters[i].y - clusters[j].y) - cos(dPhi)) / R2 ;
if (isAnti) dijTemp /= max(clusters[i].pT2, clusters[j].pT2);
else if (isKT) dijTemp *= min(clusters[i].pT2, clusters[j].pT2);
dij[i*(i-1)/2 + j] = dijTemp;
// End of original-particle loops.
}
}
// Find first particle pair to join.
findNext();