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Herwig 7.3.0
Herwig::TwoPionPhotonCurrent Class Reference

This class implements the decay current for \(\pi^\pm\pi^0 \gamma\) via an intermediate \(\omega\). More...

#include <TwoPionPhotonCurrent.h>

Inheritance diagram for Herwig::TwoPionPhotonCurrent:

Public Member Functions

 TwoPionPhotonCurrent ()
 Default constructor.
 
Methods for the construction of the phase space integrator.
virtual bool createMode (int icharge, tcPDPtr resonance, FlavourInfo flavour, unsigned int imode, PhaseSpaceModePtr mode, unsigned int iloc, int ires, PhaseSpaceChannel phase, Energy upp)
 Complete the construction of the decay mode for integration.classes inheriting from this one.
 
virtual tPDVector particles (int icharge, unsigned int imode, int iq, int ia)
 The particles produced by the current.
 
virtual vector< LorentzPolarizationVectorEcurrent (tcPDPtr resonance, FlavourInfo flavour, const int imode, const int ichan, Energy &scale, const tPDVector &outgoing, const vector< Lorentz5Momentum > &momenta, DecayIntegrator::MEOption meopt) const
 Hadronic current.
 
virtual void constructSpinInfo (ParticleVector decay) const
 Construct the SpinInfo for the decay products.
 
virtual bool accept (vector< int > id)
 Accept the decay.
 
virtual unsigned int decayMode (vector< int > id)
 Return the decay mode number for a given set of particles in the current.
 
virtual void dataBaseOutput (ofstream &os, bool header, bool create) const
 Output the setup information for the particle database.
 
- Public Member Functions inherited from Herwig::WeakCurrent
 WeakCurrent ()
 Default constructor.
 
unsigned int numberOfModes () const
 Return the number of modes handled by this current.
 
void decayModeInfo (unsigned int imode, int &iq, int &ia) const
 Information on a decay mode.
 
void persistentOutput (PersistentOStream &os) const
 Function used to write out object persistently.
 
void persistentInput (PersistentIStream &is, int version)
 Function used to read in object persistently.
 
- Public Member Functions inherited from ThePEG::Interfaced
virtual bool defaultInit ()
 
PPtr getParticle (PID) const
 
PDPtr getParticleData (PID) const
 
bool used () const
 
void useMe () const
 
tEGPtr generator () const
 
void persistentOutput (PersistentOStream &os) const
 
void persistentInput (PersistentIStream &is, int version)
 
PPtr getParticle (PID) const
 
PDPtr getParticleData (PID) const
 
bool used () const
 
void useMe () const
 
tEGPtr generator () const
 
- Public Member Functions inherited from ThePEG::InterfacedBase
string fullName () const
 
string name () const
 
string path () const
 
string comment () const
 
void setup (istream &is)
 
void update ()
 
void init ()
 
virtual bool preInitialize () const
 
void initrun ()
 
void finish ()
 
void touch ()
 
void reset ()
 
void clear ()
 
InitState state () const
 
bool locked () const
 
bool touched () const
 
virtual IBPtr fullclone () const
 
void persistentOutput (PersistentOStream &os) const
 
void persistentInput (PersistentIStream &is, int version)
 
virtual void debugme () const
 
void update ()
 
void init ()
 
virtual bool preInitialize () const
 
void initrun ()
 
void finish ()
 
void touch ()
 
void reset ()
 
void clear ()
 
InitState state () const
 
bool locked () const
 
bool touched () const
 
virtual IBPtr fullclone () const
 
- Public Member Functions inherited from ThePEG::Base
void debug () const
 
virtual void debugme () const
 
- Public Member Functions inherited from ThePEG::Pointer::ReferenceCounted
CounterType referenceCount () const
 
- Public Member Functions inherited from ThePEG::Named
 Named (const string &newName=string())
 
 Named (const Named &)=default
 
const string & name () const
 
bool operator== (const Named &other) const
 
bool operator< (const Named &other) const
 

Clone Methods.

Energy2 _grho
 Coupling of the rho to the photon, \(F_\rho\).
 
InvEnergy _grhoomegapi
 Coupling of the rho to the omega and a pion, \(g_{\rho\omega\pi}\).
 
vector< double > _resweights
 Weights of the different rho resonances in the current.
 
vector< Energy > _rhomasses
 Masses of the \(\rho\) resonances.
 
vector< Energy > _rhowidths
 Widths of the \(\rho\) resonances.
 
Energy _omegamass
 The \(\omega\) mass.
 
Energy _omegawidth
 The \(\omega\) width.
 
Energy _intmass
 Mass for the intermediate in the phase-space, this is a technical parameter to improve the phase-space integration efficiency.
 
Energy _intwidth
 Width for the intermediate in the phase-space, this is a technical parameter to improve the phase-space integration efficiency.
 
virtual IBPtr clone () const
 Make a simple clone of this object.
 
virtual IBPtr fullclone () const
 Make a clone of this object, possibly modifying the cloned object to make it sane.
 
TwoPionPhotonCurrentoperator= (const TwoPionPhotonCurrent &)=delete
 Private and non-existent assignment operator.
 
complex< InvEnergy > FFunction (Energy2 q2) const
 Calculate the \(F(q^2)\) function at a given scale.
 
complex< InvEnergy2 > BreitWigner (Energy2 q2, unsigned int ires) const
 Fixed width Breit wigner.
 

Functions used by the persistent I/O system.

void persistentOutput (PersistentOStream &os) const
 Function used to write out object persistently.
 
void persistentInput (PersistentIStream &is, int version)
 Function used to read in object persistently.
 
static void Init ()
 Standard Init function used to initialize the interfaces.
 

Additional Inherited Members

- Public Types inherited from ThePEG::InterfacedBase
enum  InitState
 
- Public Types inherited from ThePEG::Pointer::ReferenceCounted
typedef unsigned int CounterType
 
- Static Public Member Functions inherited from Herwig::WeakCurrent
static void Init ()
 Standard Init function used to initialize the interfaces.
 
- Static Public Member Functions inherited from ThePEG::Interfaced
static void Init ()
 
- Static Public Member Functions inherited from ThePEG::InterfacedBase
static void Init ()
 
- Static Public Member Functions inherited from ThePEG::Base
static void Init ()
 
- Public Attributes inherited from ThePEG::InterfacedBase
 initializing
 
 uninitialized
 
 initialized
 
 runready
 
- Public Attributes inherited from ThePEG::Pointer::ReferenceCounted
const unsigned long uniqueId
 
- Protected Member Functions inherited from Herwig::WeakCurrent
void addDecayMode (int iq, int ia)
 Add a decay mode to the list.
 
void setInitialModes (unsigned int nmodes)
 Set initial number of modes.
 
- Protected Member Functions inherited from ThePEG::Interfaced
void reporeg (IBPtr object, string name) const
 
bool setDefaultReference (PtrT &ptr, string classname, string objectname)
 
 Interfaced (const string &newName)
 
 Interfaced (const Interfaced &i)
 
void setGenerator (tEGPtr generator)
 
- Protected Member Functions inherited from ThePEG::InterfacedBase
virtual void readSetup (istream &is)
 
virtual void doupdate ()
 
virtual void doinit ()
 
virtual void doinitrun ()
 
virtual void dofinish ()
 
virtual IVector getReferences ()
 
virtual void rebind (const TranslationMap &)
 
virtual IBPtr clone () const=0
 
 InterfacedBase (string newName)
 
 InterfacedBase (const InterfacedBase &i)
 
virtual void readSetup (istream &is)
 
virtual void doupdate ()
 
virtual void doinit ()
 
virtual void doinitrun ()
 
virtual void dofinish ()
 
virtual IVector getReferences ()
 
virtual void rebind (const TranslationMap &)
 
- Protected Member Functions inherited from ThePEG::Pointer::ReferenceCounted
 ReferenceCounted (const ReferenceCounted &)
 
ReferenceCountedoperator= (const ReferenceCounted &)
 
- Protected Member Functions inherited from ThePEG::Named
const Namedoperator= (const Named &other)
 
const string & name (const string &newName)
 
- Static Protected Member Functions inherited from ThePEG::Interfaced
static void registerRepository (IBPtr)
 
static void registerRepository (IBPtr, string newName)
 

Detailed Description

This class implements the decay current for \(\pi^\pm\pi^0 \gamma\) via an intermediate \(\omega\).

It inherits from the WeakCurrent class and implements the hadronic current.

The model is based on the one used in TAUOLA, Comput.Phys.Commun.76:361-380,1993. The current is given by

\[J^\mu = e T \left\{ \epsilon^\mu\left[ m^2_\pi p_1\cdot p_3 -p_2\cdot p_3(p_2\cdot p_1-p_1\cdot p_3)\right] -p_2^\mu\left[p_2\cdot\epsilon p_1\cdot p_3-p_1\cdot\epsilon p_2\cdot p_3\right] +p_3^\mu\left[\epsilon\cdot p_2-\epsilon\cdot p_1(m^2_\pi+p_2\cdotp_3)\right] *\right\}\]

where

  • \(p_1\) is the momentum of the charged pion
  • \(p_2\) is the momentum of the neutral pion
  • \(p_3\) is the momentum of the photon
  • \(\epsilon\) is the polarization of the photon
  • \(e\) is the electric charge of the positron and the normaliztion factor is

    \[T = F(q^2)F(0)\frac1{\sqrt{2}B_\omega(s_2)}\]

    and

    \[F(s) = \sqrt{2}F_\rho g_{\rho\omega\pi}\sum_k\sigma_k B_{\rho_k}(s)\]

    where
  • \(B_\omega(s)=\frac1{m^2_\omega-s-im_\omega\Gamma_\omega}\) is the Breit-Wigner for the \(\omega\).
  • \(m_\omega\) is the mass of the \(\omega\).
  • \(\Gamma_\omega \) is the width of the \(\omega\).
  • \(F_\rho\) is the coupling for the conversion of the \(\rho\) to a photon.
  • \(g_{\rho\omega\pi}\) is the coupling of \(\rho\), \(\omega\), \(\pi\).
  • \(m_{\rho_k}\) is the mass of the \(k\)th \(\rho\) resonance
  • \(B_{\rho_k}(s)=\frac1{m^2_{\rho_k}-s-im_{\rho_k}\Gamma_{\rho_k}}\) is the Breit-Wigner for \({\rho_k}\).
  • \(m_{\rho_k}\) is the mass of the \({\rho_k}\).
  • \(\Gamma_{\rho_k} \) is the width of the \({\rho_k}\).
See also
WeakCurrent
Author
Peter Richardson

Definition at line 60 of file TwoPionPhotonCurrent.h.

Member Function Documentation

◆ accept()

virtual bool Herwig::TwoPionPhotonCurrent::accept ( vector< int >  id)
virtual

Accept the decay.

Checks the meson against the list

Parameters
idThe id's of the particles in the current.
Returns
Can this current have the external particles specified.

Implements Herwig::WeakCurrent.

◆ BreitWigner()

complex< InvEnergy2 > Herwig::TwoPionPhotonCurrent::BreitWigner ( Energy2  q2,
unsigned int  ires 
) const
inlineprivate

Fixed width Breit wigner.

Parameters
q2The scame \(q^2\)
iresThe resonance required (0,1,3) are the \(\rho\)'s and 10 is the \(\omega\).
Returns
The breit wigner

Definition at line 225 of file TwoPionPhotonCurrent.h.

References _omegamass, _omegawidth, _rhomasses, and _rhowidths.

Referenced by FFunction().

◆ clone()

virtual IBPtr Herwig::TwoPionPhotonCurrent::clone ( ) const
inlineprotectedvirtual

Make a simple clone of this object.

Returns
a pointer to the new object.

Implements ThePEG::InterfacedBase.

Definition at line 187 of file TwoPionPhotonCurrent.h.

◆ constructSpinInfo()

virtual void Herwig::TwoPionPhotonCurrent::constructSpinInfo ( ParticleVector  decay) const
virtual

Construct the SpinInfo for the decay products.

Reimplemented from Herwig::WeakCurrent.

◆ createMode()

virtual bool Herwig::TwoPionPhotonCurrent::createMode ( int  icharge,
tcPDPtr  resonance,
FlavourInfo  flavour,
unsigned int  imode,
PhaseSpaceModePtr  mode,
unsigned int  iloc,
int  ires,
PhaseSpaceChannel  phase,
Energy  upp 
)
virtual

Complete the construction of the decay mode for integration.classes inheriting from this one.

This method is purely virtual and must be implemented in the classes inheriting from WeakCurrent.

Parameters
ichargeThe total charge of the outgoing particles in the current.
resonanceIf specified only include terms with this particle
flavourInformation on the required flavours of the quarks
imodeThe mode in the current being asked for.
modeThe phase space mode for the integration
ilocThe location of the of the first particle from the current in the list of outgoing particles.
iresThe location of the first intermediate for the current.
phaseThe prototype phase space channel for the integration.
uppThe maximum possible mass the particles in the current are allowed to have.
Returns
Whether the current was sucessfully constructed.

Implements Herwig::WeakCurrent.

◆ current()

virtual vector< LorentzPolarizationVectorE > Herwig::TwoPionPhotonCurrent::current ( tcPDPtr  resonance,
FlavourInfo  flavour,
const int  imode,
const int  ichan,
Energy &  scale,
const tPDVector outgoing,
const vector< Lorentz5Momentum > &  momenta,
DecayIntegrator::MEOption  meopt 
) const
virtual

Hadronic current.

This method is purely virtual and must be implemented in all classes inheriting from this one.

Parameters
resonanceIf specified only include terms with this particle
flavourInformation on the required flavours of the quarks
imodeThe mode
ichanThe phase-space channel the current is needed for.
scaleThe invariant mass of the particles in the current.
outgoingThe particles produced in the decay
momentaThe momenta of the particles produced in the decay
meoptOption for the calculation of the matrix element
Returns
The current.

Implements Herwig::WeakCurrent.

◆ dataBaseOutput()

virtual void Herwig::TwoPionPhotonCurrent::dataBaseOutput ( ofstream &  os,
bool  header,
bool  create 
) const
virtual

Output the setup information for the particle database.

Parameters
osThe stream to output the information to
headerWhether or not to output the information for MySQL
createWhether or not to add a statement creating the object

Reimplemented from Herwig::WeakCurrent.

◆ decayMode()

virtual unsigned int Herwig::TwoPionPhotonCurrent::decayMode ( vector< int >  id)
virtual

Return the decay mode number for a given set of particles in the current.

Checks the meson against the list

Parameters
idThe id's of the particles in the current.
Returns
The number of the mode

Implements Herwig::WeakCurrent.

◆ FFunction()

complex< InvEnergy > Herwig::TwoPionPhotonCurrent::FFunction ( Energy2  q2) const
inlineprivate

Calculate the \(F(q^2)\) function at a given scale.

Parameters
q2The scale \(q^2\).
Returns
The value of the function.

Definition at line 210 of file TwoPionPhotonCurrent.h.

References _grho, _grhoomegapi, _resweights, BreitWigner(), ThePEG::sqrt(), and ThePEG::ZERO.

◆ fullclone()

virtual IBPtr Herwig::TwoPionPhotonCurrent::fullclone ( ) const
inlineprotectedvirtual

Make a clone of this object, possibly modifying the cloned object to make it sane.

Returns
a pointer to the new object.

Reimplemented from ThePEG::InterfacedBase.

Definition at line 193 of file TwoPionPhotonCurrent.h.

◆ particles()

virtual tPDVector Herwig::TwoPionPhotonCurrent::particles ( int  icharge,
unsigned int  imode,
int  iq,
int  ia 
)
virtual

The particles produced by the current.

This just returns the pseudoscalar meson.

Parameters
ichargeThe total charge of the particles in the current.
imodeThe mode for which the particles are being requested
iqThe PDG code for the quark
iaThe PDG code for the antiquark
Returns
The external particles for the current.

Implements Herwig::WeakCurrent.

◆ persistentInput()

void Herwig::TwoPionPhotonCurrent::persistentInput ( PersistentIStream is,
int  version 
)

Function used to read in object persistently.

Parameters
isthe persistent input stream read from.
versionthe version number of the object when written.

◆ persistentOutput()

void Herwig::TwoPionPhotonCurrent::persistentOutput ( PersistentOStream os) const

Function used to write out object persistently.

Parameters
osthe persistent output stream written to.

Member Data Documentation

◆ _grho

Energy2 Herwig::TwoPionPhotonCurrent::_grho
private

Coupling of the rho to the photon, \(F_\rho\).

Definition at line 243 of file TwoPionPhotonCurrent.h.

Referenced by FFunction().

◆ _grhoomegapi

InvEnergy Herwig::TwoPionPhotonCurrent::_grhoomegapi
private

Coupling of the rho to the omega and a pion, \(g_{\rho\omega\pi}\).

Definition at line 248 of file TwoPionPhotonCurrent.h.

Referenced by FFunction().

◆ _intmass

Energy Herwig::TwoPionPhotonCurrent::_intmass
private

Mass for the intermediate in the phase-space, this is a technical parameter to improve the phase-space integration efficiency.

Definition at line 279 of file TwoPionPhotonCurrent.h.

◆ _intwidth

Energy Herwig::TwoPionPhotonCurrent::_intwidth
private

Width for the intermediate in the phase-space, this is a technical parameter to improve the phase-space integration efficiency.

Definition at line 285 of file TwoPionPhotonCurrent.h.

◆ _omegamass

Energy Herwig::TwoPionPhotonCurrent::_omegamass
private

The \(\omega\) mass.

Definition at line 268 of file TwoPionPhotonCurrent.h.

Referenced by BreitWigner().

◆ _omegawidth

Energy Herwig::TwoPionPhotonCurrent::_omegawidth
private

The \(\omega\) width.

Definition at line 273 of file TwoPionPhotonCurrent.h.

Referenced by BreitWigner().

◆ _resweights

vector<double> Herwig::TwoPionPhotonCurrent::_resweights
private

Weights of the different rho resonances in the current.

Definition at line 253 of file TwoPionPhotonCurrent.h.

Referenced by FFunction().

◆ _rhomasses

vector<Energy> Herwig::TwoPionPhotonCurrent::_rhomasses
private

Masses of the \(\rho\) resonances.

Definition at line 258 of file TwoPionPhotonCurrent.h.

Referenced by BreitWigner().

◆ _rhowidths

vector<Energy> Herwig::TwoPionPhotonCurrent::_rhowidths
private

Widths of the \(\rho\) resonances.

Definition at line 263 of file TwoPionPhotonCurrent.h.

Referenced by BreitWigner().


The documentation for this class was generated from the following file: