+++ /dev/null
-// MultipartonInteractions.h is a part of the PYTHIA event generator.
-// Copyright (C) 2012 Torbjorn Sjostrand.
-// PYTHIA is licenced under the GNU GPL version 2, see COPYING for details.
-// Please respect the MCnet Guidelines, see GUIDELINES for details.
-
-// This file contains the main classes for multiparton interactions physics.
-// SigmaMultiparton stores allowed processes by in-flavour combination.
-// MultipartonInteractions: generates multiparton parton-parton interactions.
-
-#ifndef Pythia8_MultipartonInteractions_H
-#define Pythia8_MultipartonInteractions_H
-
-#include "Basics.h"
-#include "BeamParticle.h"
-#include "Event.h"
-#include "Info.h"
-#include "PartonSystems.h"
-#include "PythiaStdlib.h"
-#include "Settings.h"
-#include "SigmaTotal.h"
-#include "SigmaProcess.h"
-#include "StandardModel.h"
-#include "UserHooks.h"
-
-namespace Pythia8 {
-
-//==========================================================================
-
-// SigmaMultiparton is a helper class to MultipartonInteractions.
-// It packs pointers to the allowed processes for different
-// flavour combinations and levels of ambition.
-
-class SigmaMultiparton {
-
-public:
-
- // Constructor.
- SigmaMultiparton() {}
-
- // Destructor.
- ~SigmaMultiparton() {
- for (int i = 0; i < int(sigmaT.size()); ++i) delete sigmaT[i];
- for (int i = 0; i < int(sigmaU.size()); ++i) delete sigmaU[i];}
-
- // Initialize list of processes.
- bool init(int inState, int processLevel, Info* infoPtr,
- Settings* settingsPtr, ParticleData* particleDataPtr, Rndm* rndmPtrIn,
- BeamParticle* beamAPtr, BeamParticle* beamBPtr, Couplings* couplingsPtr);
-
- // Calculate cross section summed over possibilities.
- double sigma( int id1, int id2, double x1, double x2, double sHat,
- double tHat, double uHat, double alpS, double alpEM,
- bool restore = false, bool pickOtherIn = false);
-
- // Return whether the other, rare processes were selected.
- bool pickedOther() {return pickOther;}
-
- // Return one subprocess, picked according to relative cross sections.
- SigmaProcess* sigmaSel();
- bool swapTU() {return pickedU;}
-
- // Return code or name of a specified process, for statistics table.
- int nProc() const {return nChan;}
- int codeProc(int iProc) const {return sigmaT[iProc]->code();}
- string nameProc(int iProc) const {return sigmaT[iProc]->name();}
-
-private:
-
- // Constants: could only be changed in the code itself.
- static const double MASSMARGIN, OTHERFRAC;
-
- // Number of processes. Some use massive matrix elements.
- int nChan;
- vector<bool> needMasses;
- vector<double> m3Fix, m4Fix, sHatMin;
-
- // Vector of process list, one for t-channel and one for u-channel.
- vector<SigmaProcess*> sigmaT, sigmaU;
-
- // Values of cross sections in process list above.
- vector<double> sigmaTval, sigmaUval;
- double sigmaTsum, sigmaUsum;
- bool pickOther, pickedU;
-
- // Pointer to the random number generator.
- Rndm* rndmPtr;
-
-};
-
-//==========================================================================
-
-// The MultipartonInteractions class contains the main methods for the
-// generation of multiparton parton-parton interactions in hadronic collisions.
-
-class MultipartonInteractions {
-
-public:
-
- // Constructor.
- MultipartonInteractions() : bIsSet(false) {}
-
- // Initialize the generation process for given beams.
- bool init( bool doMPIinit, int iDiffSysIn, Info* infoPtrIn,
- Settings& settings, ParticleData* particleDataPtr, Rndm* rndmPtrIn,
- BeamParticle* beamAPtrIn, BeamParticle* beamBPtrIn,
- Couplings* couplingsPtrIn, PartonSystems* partonSystemsPtrIn,
- SigmaTotal* sigmaTotPtrIn, UserHooks* userHooksPtrIn,
- ostream& os = cout);
-
- // Reset impact parameter choice and update the CM energy.
- void reset();
-
- // Select first = hardest pT in minbias process.
- void pTfirst();
-
- // Set up kinematics for first = hardest pT in minbias process.
- void setupFirstSys( Event& process);
-
- // Find whether to limit maximum scale of emissions.
- bool limitPTmax( Event& event);
-
- // Prepare system for evolution.
- void prepare(Event& event, double pTscale = 1000.) {
- if (!bSetInFirst) overlapNext(event, pTscale); }
-
- // Select next pT in downwards evolution.
- double pTnext( double pTbegAll, double pTendAll, Event& event);
-
- // Set up kinematics of acceptable interaction.
- bool scatter( Event& event);
-
- // Set "empty" values to avoid query of undefined quantities.
- void setEmpty() {pT2Ren = alpS = alpEM = x1 = x2 = pT2Fac
- = xPDF1now = xPDF2now = 0.; bIsSet = false;}
-
- // Get some information on current interaction.
- double Q2Ren() const {return pT2Ren;}
- double alphaSH() const {return alpS;}
- double alphaEMH() const {return alpEM;}
- double x1H() const {return x1;}
- double x2H() const {return x2;}
- double Q2Fac() const {return pT2Fac;}
- double pdf1() const {return xPDF1now;}
- double pdf2() const {return xPDF2now;}
- double bMPI() const {return (bIsSet) ? bNow / bAvg : 0.;}
- double enhanceMPI() const {return (bIsSet) ? enhanceB / zeroIntCorr : 1.;}
-
- // For x-dependent matter profile, return incoming valence/sea
- // decision from trial interactions.
- int getVSC1() const {return vsc1;}
- int getVSC2() const {return vsc2;}
-
- // Update and print statistics on number of processes.
- // Note: currently only valid for MB systems, not diffraction??
- void accumulate() { int iBeg = (infoPtr->isMinBias()) ? 0 : 1;
- for (int i = iBeg; i < infoPtr->nMPI(); ++i)
- ++nGen[ infoPtr->codeMPI(i) ];}
- void statistics(bool resetStat = false, ostream& os = cout);
- void resetStatistics() { for ( map<int, int>::iterator iter = nGen.begin();
- iter != nGen.end(); ++iter) iter->second = 0; }
-
-private:
-
- // Constants: could only be changed in the code itself.
- static const bool SHIFTFACSCALE, PREPICKRESCATTER;
- static const double SIGMAFUDGE, RPT20, PT0STEP, SIGMASTEP, PT0MIN,
- EXPPOWMIN, PROBATLOWB, BSTEP, BMAX, EXPMAX,
- KCONVERGE, CONVERT2MB, ROOTMIN, ECMDEV, WTACCWARN;
-
- // Initialization data, read from Settings.
- bool allowRescatter, allowDoubleRes, canVetoMPI;
- int pTmaxMatch, alphaSorder, alphaEMorder, bProfile, processLevel,
- rescatterMode, nQuarkIn, nSample, enhanceScreening;
- double alphaSvalue, Kfactor, pT0Ref, ecmRef, ecmPow, pTmin, coreRadius,
- coreFraction, expPow, ySepResc, deltaYResc, sigmaPomP, mPomP, pPomP,
- mMaxPertDiff, mMinPertDiff;
-
- // x-dependent matter profile:
- // Constants.
- static const int XDEP_BBIN;
- static const double XDEP_A0, XDEP_A1, XDEP_BSTEP, XDEP_BSTEPINC,
- XDEP_CUTOFF, XDEP_WARN, XDEP_SMB2FM;
-
- // Table of Int( dSigma/dX * O(b, X), dX ) in bins of b for fast
- // integration. Only needed during initialisation.
- vector <double> sigmaIntWgt, sigmaSumWgt;
-
- // a1: value of a1 constant, taken from settings database.
- // a0now (a02now): tuned value of a0 (squared value).
- // bstepNow: current size of bins in b.
- // a2max: given an xMin, a maximal (squared) value of the
- // width, to be used in overestimate Omax(b).
- // enhanceBmax, retain enhanceB as enhancement factor for the hardest
- // enhanceBnow: interaction. Use enhanceBmax as overestimate for fastPT2,
- // and enhanceBnow to store the value for the current
- // interaction.
- double a1, a0now, a02now, bstepNow, a2max, b2now, enhanceBmax, enhanceBnow;
-
- // Storage for trial interactions.
- int id1Save, id2Save;
- double pT2Save, x1Save, x2Save, sHatSave, tHatSave, uHatSave,
- alpSsave, alpEMsave, pT2FacSave, pT2RenSave, xPDF1nowSave,
- xPDF2nowSave;
- SigmaProcess *dSigmaDtSelSave;
-
- // vsc1, vsc2: for minimum-bias events with trial interaction, store
- // decision on whether hard interaction was valence or sea.
- int vsc1, vsc2;
-
- // Other initialization data.
- bool hasBaryonBeams, hasLowPow, globalRecoilFSR;
- int iDiffSys, nMaxGlobalRecoilFSR;
- double eCM, sCM, pT0, pT20, pT2min, pTmax, pT2max, pT20R, pT20minR,
- pT20maxR, pT20min0maxR, pT2maxmin, sigmaND, pT4dSigmaMax,
- pT4dProbMax, dSigmaApprox, sigmaInt, sudExpPT[101],
- zeroIntCorr, normOverlap, nAvg, kNow, normPi, bAvg, bDiv,
- probLowB, radius2B, radius2C, fracA, fracB, fracC, fracAhigh,
- fracBhigh, fracChigh, fracABChigh, expRev, cDiv, cMax;
-
- // Properties specific to current system.
- bool bIsSet, bSetInFirst, isAtLowB, pickOtherSel;
- int id1, id2, i1Sel, i2Sel, id1Sel, id2Sel;
- double bNow, enhanceB, pT2, pT2shift, pT2Ren, pT2Fac, x1, x2, xT, xT2,
- tau, y, sHat, tHat, uHat, alpS, alpEM, xPDF1now, xPDF2now,
- dSigmaSum, x1Sel, x2Sel, sHatSel, tHatSel, uHatSel;
-
- // Stored values for mass interpolation for diffractive systems.
- int nStep, iStepFrom, iStepTo;
- double eCMsave, eStepSize, eStepSave, eStepFrom, eStepTo, pT0Save[5],
- pT4dSigmaMaxSave[5], pT4dProbMaxSave[5], sigmaIntSave[5],
- sudExpPTSave[5][101], zeroIntCorrSave[5], normOverlapSave[5],
- kNowSave[5], bAvgSave[5], bDivSave[5], probLowBSave[5],
- fracAhighSave[5], fracBhighSave[5], fracChighSave[5],
- fracABChighSave[5], cDivSave[5], cMaxSave[5];
-
- // Pointer to various information on the generation.
- Info* infoPtr;
-
- // Pointer to the random number generator.
- Rndm* rndmPtr;
-
- // Pointers to the two incoming beams.
- BeamParticle* beamAPtr;
- BeamParticle* beamBPtr;
-
- // Pointers to Standard Model couplings.
- Couplings* couplingsPtr;
-
- // Pointer to information on subcollision parton locations.
- PartonSystems* partonSystemsPtr;
-
- // Pointer to total cross section parametrization.
- SigmaTotal* sigmaTotPtr;
-
- // Pointer to user hooks.
- UserHooks* userHooksPtr;
-
- // Collections of parton-level 2 -> 2 cross sections. Selected one.
- SigmaMultiparton sigma2gg, sigma2qg, sigma2qqbarSame, sigma2qq;
- SigmaMultiparton* sigma2Sel;
- SigmaProcess* dSigmaDtSel;
-
- // Statistics on generated 2 -> 2 processes.
- map<int, int> nGen;
-
- // alphaStrong and alphaEM calculations.
- AlphaStrong alphaS;
- AlphaEM alphaEM;
-
- // Scattered partons.
- vector<int> scatteredA, scatteredB;
-
- // Determine constant in d(Prob)/d(pT2) < const / (pT2 + r * pT20)^2.
- void upperEnvelope();
-
- // Integrate the parton-parton interaction cross section.
- void jetCrossSection();
-
- // Evaluate "Sudakov form factor" for not having a harder interaction.
- double sudakov(double pT2sud, double enhance = 1.);
-
- // Do a quick evolution towards the next smaller pT.
- double fastPT2( double pT2beg);
-
- // Calculate the actual cross section, either for the first interaction
- // (including at initialization) or for any subsequent in the sequence.
- double sigmaPT2scatter(bool isFirst = false);
-
- // Find the partons that may rescatter.
- void findScatteredPartons( Event& event);
-
- // Calculate the actual cross section for a rescattering.
- double sigmaPT2rescatter( Event& event);
-
- // Calculate factor relating matter overlap and interaction rate.
- void overlapInit();
-
- // Pick impact parameter and interaction rate enhancement,
- // either before the first interaction (for minbias) or after it.
- void overlapFirst();
- void overlapNext(Event& event, double pTscale);
-
-};
-
-//==========================================================================
-
-} // end namespace Pythia8
-
-#endif // Pythia8_MultipartonInteractions_H
git://git.uio.no / u / mrichter / AliRoot.git / blobdiff