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QTildeReconstructor.h
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// -*- C++ -*-
//
// QTildeReconstructor.h is a part of Herwig++ - A multi-purpose Monte Carlo event generator
// Copyright (C) 2002-2007 The Herwig Collaboration
//
// Herwig++ is licenced under version 2 of the GPL, see COPYING for details.
// Please respect the MCnet academic guidelines, see GUIDELINES for details.
//
#ifndef HERWIG_QTildeReconstructor_H
#define HERWIG_QTildeReconstructor_H
//
// This is the declaration of the QTildeReconstructor class.
//
#include "Herwig++/Shower/Base/KinematicsReconstructor.h"
#include "ThePEG/Repository/UseRandom.h"
namespace Herwig {
using namespace ThePEG;
/** \ingroup Shower
* A simple struct to store the information we need on the
* showering
*/
struct JetKinStruct {
/**
* Parent particle of the jet
*/
tShowerParticlePtr parent;
/**
* Momentum of the particle before reconstruction
*/
Lorentz5Momentum p;
/**
* Momentum of the particle after reconstruction
*/
Lorentz5Momentum q;
};
/**
* typedef for a vector of JetKinStruct
*/
typedef vector<JetKinStruct> JetKinVect;
/** \ingroup Shower
*
* This class is responsible for the kinematical reconstruction
* after each showering step, and also for the necessary Lorentz boosts
* in order to preserve energy-momentum conservation in the overall collision,
* and also the invariant mass and the rapidity of the hard subprocess system.
* In the case of multi-step showering, there will be not unnecessary
* kinematical reconstructions.
*
* There is also the option of taking a set of momenta for the particles
* and inverting the reconstruction to give the evolution variables for the
* shower.
*
* Notice:
* - although we often use the term "jet" in either methods or variables names,
* or in comments, which could appear applicable only for QCD showering,
* there is indeed no "dynamics" represented in this class: only kinematics
* is involved, as the name of this class remainds. Therefore it can be used
* for any kind of showers (QCD-,QED-,EWK-,... bremsstrahlung).
*
* @see ShowerParticle
* @see ShowerKinematics
* @see \ref QTildeReconstructorInterfaces "The interfaces"
* defined for QTildeReconstructor.
*/
class QTildeReconstructor: public KinematicsReconstructor {
public:
/**
* Default constructor
*/
inline QTildeReconstructor() : _reconopt(0) {};
/**
* Methods to reconstruct the kinematics of a scattering or decay process
*/
//@{
/**
* Given in input a vector of the particles which initiated the showers
* the method does the reconstruction of such jets,
* including the appropriate boosts (kinematics reshufflings)
* needed to conserve the total energy-momentum of the collision
* and preserving the invariant mass and the rapidity of the
* hard subprocess system.
*/
virtual bool reconstructHardJets(ShowerTreePtr hard,
const map<tShowerProgenitorPtr,
pair<Energy,double> > & pt) const;
/**
* Given in input a vector of the particles which initiated the showers
* the method does the reconstruction of such jets,
* including the appropriate boosts (kinematics reshufflings)
* needed to conserve the total energy-momentum of the collision
* and preserving the invariant mass and the rapidity of the
* hard subprocess system.
*/
virtual bool reconstructDecayJets(ShowerTreePtr decay) const;
//@}
/**
* Methods to invert the reconstruction of the shower for
* a scattering or decay process and calculate
* the variables used to generate the
* shower given the particles produced.
* This is needed for the CKKW and POWHEG approaches
*/
//@{
/**
* Given the particles, with a history which we wish to interpret
* as a shower reconstruct the variables used to generate the
* shower
*/
virtual bool deconstructDecayJets(HardTreePtr, EvolverPtr) const;
/**
* Given the particles, with a history which we wish to interpret
* as a shower reconstruct the variables used to generate the shower
* for a hard process
*/
virtual bool deconstructHardJets(HardTreePtr, EvolverPtr) const;
//@}
public:
/** @name Functions used by the persistent I/O system. */
//@{
/**
* Function used to write out object persistently.
* @param os the persistent output stream written to.
*/
void persistentOutput(PersistentOStream & os) const;
/**
* Function used to read in object persistently.
* @param is the persistent input stream read from.
* @param version the version number of the object when written.
*/
void persistentInput(PersistentIStream & is, int version);
//@}
/**
* The standard Init function used to initialize the interfaces.
* Called exactly once for each class by the class description system
* before the main function starts or
* when this class is dynamically loaded.
*/
static void Init();
protected:
/**
* Methods to reconstruct the kinematics of individual jets
*/
//@{
/**
* Given the particle (ShowerParticle object) that
* originates a forward (time-like) jet, this method reconstructs the kinematics
* of the jet. That is, by starting from the final grand-children (which
* originates directly or indirectly from particleJetParent,
* and which don't have children), and moving "backwards" (in a physical
* time picture), towards the particleJetParent, the
* ShowerKinematics objects associated with the various particles,
* which have been created during the showering, are now completed.
* In particular, at the end, we get the mass of the jet, which is the
* main information we want.
* This methods returns false if there was no radiation or rescaling required
*/
virtual bool reconstructTimeLikeJet(const tShowerParticlePtr particleJetParent,
unsigned int iopt) const;
/**
* Exactly similar to the previous one, but for a space-like jet.
* Also in this case we start from the final grand-children (which
* are childless) of the particle which originates the jet, but in
* this case we proceed "forward" (in the physical time picture)
* towards the particleJetParent.
* This methods returns false if there was no radiation or rescaling required
*/
bool reconstructSpaceLikeJet(const tShowerParticlePtr particleJetParent) const;
/**
* Exactly similar to the previous one, but for a decay jet
* This methods returns false if there was no radiation or rescaling required
*/
bool reconstructDecayJet(const tShowerParticlePtr particleJetParent) const;
//@}
/**
* Given a vector of 5-momenta of jets, where the 3-momenta are the initial
* ones before showering and the masses are reconstructed after the showering,
* this method returns the overall scaling factor for the 3-momenta of the
* vector of particles, vec{P}_i -> k * vec{P}_i, such to preserve energy-
* momentum conservation, i.e. after the rescaling the center of mass 5-momentum
* is equal to the one specified in input, cmMomentum.
* The method returns 0 if such factor cannot be found.
* @param root_s Centre-of-mass energy
* @param jets The jets
*/
double solveKfactor( const Energy & root_s, const JetKinVect & jets ) const;
/**
* Calculate the rescaling factors for the jets in a particle decay where
* there was initial-state radiation
* @param mb The mass of the decaying particle
* @param n The reference vector for the initial state radiation
* @param pjet The momentum of the initial-state jet
* @param jetKinematics The JetKinStruct objects for the jets
* @param partner The colour partner
* @param ppartner The momentum of the colour partner of the decaying particle
* before and after radiation
* @param k1 The rescaling parameter for the partner
* @param k2 The rescaling parameter for the outgoing singlet
* @param qt The transverse momentum vector
*/
bool solveDecayKFactor(Energy mb, Lorentz5Momentum n, Lorentz5Momentum pjet,
const JetKinVect & jetKinematics, ShowerParticlePtr partner,
Lorentz5Momentum ppartner[2],
double & k1, double & k2,Lorentz5Momentum & qt) const;
/**
* Compute the momentum rescaling factor needed to invert the shower
* @param pout The momenta of the outgoing particles
* @param mon The on-shell masses
* @param roots The mass of the decaying particle
*/
double inverseRescalingFactor(vector<Lorentz5Momentum> pout,
vector<Energy> mon,Energy roots) const;
/**
* Check the rescaling conserves momentum
* @param k The rescaling
* @param root_s The centre-of-mass energy
* @param jets The jets
*/
Energy momConsEq(const double & k, const Energy & root_s,
const JetKinVect & jets) const;
/**
* Compute the boost to get from the the old momentum to the new
*/
LorentzRotation solveBoost(const double k, const Lorentz5Momentum & newq,
const Lorentz5Momentum & oldp) const;
/**
* Compute the boost to get from the the old momentum to the new
*/
LorentzRotation solveBoost(const Lorentz5Momentum & newq,
const Lorentz5Momentum & oldq) const;
/**
* Recursively boost the initial-state shower
* @param p The particle
* @param bv The boost
* @param parent The parent of the chain
*/
inline void boostChain(tPPtr p, const LorentzRotation & bv, tPPtr & parent) const;
/**
* Given a 5-momentum and a scale factor, the method returns the
* Lorentz boost that transforms the 3-vector vec{momentum} --->
* k*vec{momentum}. The method returns the null boost in the case no
* solution exists. This will only work in the case where the
* outgoing jet-momenta are parallel to the momenta of the particles
* leaving the hard subprocess.
*/
Boost solveBoostBeta( const double k, const Lorentz5Momentum & newq,
const Lorentz5Momentum & oldp);
/**
* Compute boost parameter along z axis to get (Ep, any perp, qp)
* from (E, same perp, q).
*/
inline double getBeta(const double E, const double q,
const double Ep, const double qp) const
{return (q*E-qp*Ep)/(sqr(qp)+sqr(E));}
/**
* Find the colour partners of a particle to identify the colour singlet
* systems.
*/
vector<unsigned int> findPartners(unsigned int ,vector<ShowerProgenitorPtr>) const;
/**
* Perform the reconstruction of a system with one incoming and at least one
* outgoing particle
*/
void reconstructInitialFinalSystem(vector<ShowerProgenitorPtr>) const;
/**
* Perform the reconstruction of a system with only final-state
* particles
*/
void reconstructFinalStateSystem(bool applyBoost, Boost toRest, Boost fromRest,
vector<ShowerProgenitorPtr>) const;
/**
* Perform the reconstruction of a system with only final-state
* particles
*/
void reconstructFinalStateShower(Boost & toRest, Boost & fromRest,
HardTreePtr,
vector<HardBranchingPtr>,
EvolverPtr ) const;
/**
* Perform the reconstruction of a system with only final-state
* particles
*/
void reconstructInitialInitialSystem(bool & applyBoost,
Boost & toRest, Boost & fromRest,
vector<ShowerProgenitorPtr>) const;
/**
* Perform the reconstruction of a system with only final-state
* particles
*/
void reconstructInitialInitialShower(bool & applyBoost,
Boost & toRest, Boost & fromRest,
HardTreePtr,
vector<HardBranchingPtr> ) const;
/**
* Reconstruction of a general coloured system
*/
void reconstructGeneralSystem(vector<ShowerProgenitorPtr> & ShowerHardJets) const;
/**
* Add the intrinsic \f$p_T\f$ to the system if needed
*/
bool addIntrinsicPt(vector<ShowerProgenitorPtr>) const;
protected:
/** @name Clone Methods. */
//@{
/**
* Make a simple clone of this object.
* @return a pointer to the new object.
*/
inline virtual IBPtr clone() const {return new_ptr(*this);}
/** Make a clone of this object, possibly modifying the cloned object
* to make it sane.
* @return a pointer to the new object.
*/
inline virtual IBPtr fullclone() const {return new_ptr(*this);}
//@}
private:
/**
* The static object used to initialize the description of this class.
* Indicates that this is an concrete class without persistent data.
*/
static ClassDescription<QTildeReconstructor> initQTildeReconstructor;
/**
* The assignment operator is private and must never be called.
* In fact, it should not even be implemented.
*/
QTildeReconstructor & operator=(const QTildeReconstructor &);
private:
/**
* Option for handling the reconstruction
*/
unsigned int _reconopt;
/**
* The progenitor of the jet currently being reconstructed
*/
mutable tShowerParticlePtr _progenitor;
/**
* Storage of the intrinsic \f$p_T\f$
*/
mutable map<tShowerProgenitorPtr,pair<Energy,double> > _intrinsic;
};
}
#include "ThePEG/Utilities/ClassTraits.h"
namespace ThePEG {
/** @cond TRAITSPECIALIZATIONS */
/** This template specialization informs ThePEG about the
* base classes of QTildeReconstructor. */
template <>
struct BaseClassTrait<Herwig::QTildeReconstructor,1> {
/** Typedef of the first base class of QTildeReconstructor. */
typedef Herwig::KinematicsReconstructor NthBase;
};
/** This template specialization informs ThePEG about the name of
* the QTildeReconstructor class and the shared object where it is defined. */
template <>
struct ClassTraits<Herwig::QTildeReconstructor>
: public ClassTraitsBase<Herwig::QTildeReconstructor> {
/** Return a platform-independent class name */
static string className() { return "Herwig::QTildeReconstructor"; }
/**
* The name of a file containing the dynamic library where the class
* QTildeReconstructor is implemented. It may also include several, space-separated,
* libraries if the class QTildeReconstructor depends on other classes (base classes
* excepted). In this case the listed libraries will be dynamically
* linked in the order they are specified.
*/
static string library() { return "HwShower.so"; }
};
/** @endcond */
}
#endif /* HERWIG_QTildeReconstructor_H */

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