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Herwig  7.1.4

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.
 
virtual vector< LorentzPolarizationVectorEcurrent (const int imode, const int ichan, Energy &scale, const ParticleVector &decay, DecayIntegrator::MEOption meopt) const
 Hadronic current. More...
 
virtual bool accept (vector< int > id)
 Accept the decay. More...
 
virtual unsigned int decayMode (vector< int > id)
 Return the decay mode number for a given set of particles in the current. More...
 
virtual void dataBaseOutput (ofstream &os, bool header, bool create) const
 Output the setup information for the particle database. More...
 
Functions used by the persistent I/O system.
void persistentOutput (PersistentOStream &os) const
 Function used to write out object persistently. More...
 
void persistentInput (PersistentIStream &is, int version)
 Function used to read in object persistently. More...
 
Methods for the construction of the phase space integrator.
virtual bool createMode (int icharge, unsigned int imode, DecayPhaseSpaceModePtr mode, unsigned int iloc, unsigned int ires, DecayPhaseSpaceChannelPtr phase, Energy upp)
 Complete the construction of the decay mode for integration. More...
 
virtual tPDVector particles (int icharge, unsigned int imode, int iq, int ia)
 The particles produced by the current. More...
 
- Public Member Functions inherited from Herwig::WeakDecayCurrent
 WeakDecayCurrent ()
 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. More...
 
void persistentOutput (PersistentOStream &os) const
 Function used to write out object persistently. More...
 
void persistentInput (PersistentIStream &is, int version)
 Function used to read in object persistently. More...
 
- 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
 
void persistentOutput (PersistentOStream &os) const
 
void persistentInput (PersistentIStream &is, int version)
 
- Public Member Functions inherited from ThePEG::InterfacedBase
string fullName () const
 
string name () const
 
string path () const
 
string comment () const
 
void setup (istream &is)
 
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
 
void persistentOutput (PersistentOStream &os) const
 
void persistentInput (PersistentIStream &is, int version)
 
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
 
void persistentOutput (PersistentOStream &os) const
 
void persistentInput (PersistentIStream &is, int version)
 
- Public Member Functions inherited from ThePEG::Base
void debug () const
 
- Public Member Functions inherited from ThePEG::Pointer::ReferenceCounted
CounterType referenceCount () const
 
- Public Member Functions inherited from ThePEG::Named
 Named (const string &newName=string())
 
const string & name () const
 
bool operator== (const Named &other) const
 
bool operator< (const Named &other) const
 

Static Public Member Functions

static void Init ()
 Standard Init function used to initialize the interfaces.
 
- Static Public Member Functions inherited from Herwig::WeakDecayCurrent
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 ()
 

Protected Member Functions

Clone Methods.
virtual IBPtr clone () const
 Make a simple clone of this object. More...
 
virtual IBPtr fullclone () const
 Make a clone of this object, possibly modifying the cloned object to make it sane. More...
 
Standard Interfaced functions.
virtual void doinit ()
 Initialize this object after the setup phase before saving and EventGenerator to disk. More...
 
- Protected Member Functions inherited from Herwig::WeakDecayCurrent
void addDecayMode (int iq, int ia)
 Add a decay mode to the list. More...
 
void setInitialModes (unsigned int nmodes)
 Set initial number of modes. More...
 
- 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
 InterfacedBase (string newName)
 
 InterfacedBase (const InterfacedBase &i)
 
virtual void readSetup (istream &is)
 
virtual void doupdate ()
 
virtual void doinitrun ()
 
virtual void dofinish ()
 
virtual IVector getReferences ()
 
virtual void rebind (const TranslationMap &)
 
virtual void readSetup (istream &is)
 
virtual void doupdate ()
 
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 &)
 
 ReferenceCounted (const ReferenceCounted &)
 
ReferenceCountedoperator= (const ReferenceCounted &)
 
- Protected Member Functions inherited from ThePEG::Named
const Namedoperator= (const Named &other)
 
const string & name (const string &newName)
 

Private Member Functions

TwoPionPhotonCurrentoperator= (const TwoPionPhotonCurrent &)
 Private and non-existent assignment operator.
 
complex< InvEnergy > FFunction (Energy2 q2) const
 Calculate the $F(q^2)$ function at a given scale. More...
 
complex< InvEnergy2 > BreitWigner (Energy2 q2, unsigned int ires) const
 Fixed width Breit wigner. More...
 

Private Attributes

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.
 
bool _rhoparameters
 Use local parameters for the rho resonances rather than from the particle data objects.
 
vector< Energy > _rhomasses
 Masses of the $\rho$ resonances.
 
vector< Energy > _rhowidths
 Widths of the $\rho$ resonances.
 
bool _omegaparameters
 use local parameters for the omega rather than from the particle data objects
 
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.
 

Static Private Attributes

static ClassDescription< TwoPionPhotonCurrentinitTwoPionPhotonCurrent
 Describe a concrete class with persistent data.
 

Additional Inherited Members

- Public Types inherited from ThePEG::InterfacedBase
enum  InitState
 
- Public Types inherited from ThePEG::Pointer::ReferenceCounted
typedef unsigned int CounterType
 
- Public Attributes inherited from ThePEG::InterfacedBase
 initializing
 
 uninitialized
 
 initialized
 
 runready
 
- Public Attributes inherited from ThePEG::Pointer::ReferenceCounted
const unsigned long uniqueId
 
- 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 WeakDecayCurrent 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
WeakDecayCurrent
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::WeakDecayCurrent.

◆ 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.

◆ 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 170 of file TwoPionPhotonCurrent.h.

◆ createMode()

virtual bool Herwig::TwoPionPhotonCurrent::createMode ( int  icharge,
unsigned int  imode,
DecayPhaseSpaceModePtr  mode,
unsigned int  iloc,
unsigned int  ires,
DecayPhaseSpaceChannelPtr  phase,
Energy  upp 
)
virtual

Complete the construction of the decay mode for integration.

This version just adds the meson as the daughter of the last resonance in the phase space channel.

Parameters
ichargeThe total charge of the outgoing particles in the current.
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::WeakDecayCurrent.

◆ current()

virtual vector<LorentzPolarizationVectorE> Herwig::TwoPionPhotonCurrent::current ( const int  imode,
const int  ichan,
Energy &  scale,
const ParticleVector decay,
DecayIntegrator::MEOption  meopt 
) const
virtual

Hadronic current.

This version returns the hadronic current described above.

Parameters
imodeThe mode
ichanThe phase-space channel the current is needed for.
scaleThe invariant mass of the particles in the current.
decayThe decay products
meoptOption for the calculation of the matrix element
Returns
The current.

Implements Herwig::WeakDecayCurrent.

◆ 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::WeakDecayCurrent.

◆ 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::WeakDecayCurrent.

◆ doinit()

virtual void Herwig::TwoPionPhotonCurrent::doinit ( )
protectedvirtual

Initialize this object after the setup phase before saving and EventGenerator to disk.

Exceptions
InitExceptionif object could not be initialized properly.

Reimplemented from ThePEG::InterfacedBase.

◆ 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 sqrt(), and 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 176 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::WeakDecayCurrent.

◆ 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.

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