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Herwig 7.3.0
Herwig::ThreeMesonCurrentBase Class Referenceabstract

This is the base class for the three meson decays of the weak current. More...

#include <ThreeMesonCurrentBase.h>

Inheritance diagram for Herwig::ThreeMesonCurrentBase:

Classes

struct  FormFactors
 Helper class for form factors. More...
 

Public Member Functions

 ThreeMesonCurrentBase ()
 Default constructor.
 
virtual vector< LorentzPolarizationVectorEcurrent (const int imode, const int ichan, Energy &scale, const ParticleVector &decay, DecayIntegrator::MEOption meopt) const
 Hadronic current.
 
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 tPDVector particles (int icharge, unsigned int imode, int iq, int ia)
 The particles produced by the current.
 
virtual void dataBaseOutput (ofstream &os, bool header, bool create) const
 Output the setup information for the particle database.
 

Static Public Member Functions

static void Init ()
 Standard Init function used to initialize the interfaces.
 

Protected Member Functions

virtual bool acceptMode (int imode) const =0
 can a particular decayer handle this type of mode
 
virtual FormFactors calculateFormFactors (const int ichan, const int imode, Energy2 q2, Energy2 s1, Energy2 s2, Energy2 s3) const =0
 Calculate the form factor for the current.
 

Private Member Functions

ThreeMesonCurrentBaseoperator= (const ThreeMesonCurrentBase &)=delete
 The assignment operator is private and must never be called.
 

Detailed Description

This is the base class for the three meson decays of the weak current.

It is designed so that the currents for the following modes can be implemented in classes inheriting from this

  • \( \pi^- \pi^- \pi^+ \), (imode=0)
  • \( \pi^0 \pi^0 \pi^- \), (imode=1)
  • \( K^- \pi^- K^+ \), (imode=2)
  • \( K^0 \pi^- \bar{K}^0\), (imode=3)
  • \( K^- \pi^0 K^0 \), (imode=4)
  • \( \pi^0 \pi^0 K^- \), (imode=5)
  • \( K^- \pi^- \pi^+ \), (imode=6)
  • \( \pi^- \bar{K}^0 \pi^0 \), (imode=7)
  • \( \pi^- \pi^0 \eta \), (imode=8)

obviously there are other modes with three pseudoscalar mesons for the decay of the weak current but this model original came from \(\tau\) decay where these are the only modes. However one case which is important is the inclusion of the mixing in the neutral kaon sector for which we include the additional currents

  • \( K^0_S \pi^- K^0_S\), (imode=9)
  • \( K^0_L \pi^- K^0_L\), (imode=10)
  • \( K^0_S \pi^- K^0_L\), (imode=11)

    In this case the current is given by

    \[ J^\mu = \left(g^{\mu\nu}-\frac{q^\mu q^\nu}{q^2}\right) \left[F_1(p_2-p_3)^\mu +F_2(p_3-p_1)^\mu+F_3(p_1-p_2)^\mu\right] +q^\mu F_4 +F_5\epsilon^{\mu\alpha\beta\gamma}p_1^\alpha p_2^\beta p_3^\gamma \]

    where

  • \(p_{1,2,3}\) are the momenta of the mesons in the order given above.
  • \(F_1,F_2,F_3,F_4,F_5\) are the form factors which must be calculated in the calculateFormFactors member which should be implemented in classes inheriting from this.
See also
WeakDecayCurrent.
Author
Peter Richardson

Definition at line 59 of file ThreeMesonCurrentBase.h.

Member Function Documentation

◆ accept()

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

Accept the decay.

Checks the mesons against the list.

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

◆ acceptMode()

virtual bool Herwig::ThreeMesonCurrentBase::acceptMode ( int  imode) const
protectedpure virtual

can a particular decayer handle this type of mode

Parameters
imodeThe mode number as given above
Returns
Whether this mode can be handled.

◆ calculateFormFactors()

virtual FormFactors Herwig::ThreeMesonCurrentBase::calculateFormFactors ( const int  ichan,
const int  imode,
Energy2  q2,
Energy2  s1,
Energy2  s2,
Energy2  s3 
) const
protectedpure virtual

Calculate the form factor for the current.

Parameters
ichanThe phase space channel
imodeThe mode
q2The scale \(q^2\) for the current.
s1The invariant mass squared of particles 2 and 3, \(s_1=m^2_{23}\).
s2The invariant mass squared of particles 1 and 3, \(s_2=m^2_{13}\).
s3The invariant mass squared of particles 1 and 2, \(s_3=m^2_{12}\).

◆ current()

virtual vector< LorentzPolarizationVectorE > Herwig::ThreeMesonCurrentBase::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.

◆ dataBaseOutput()

virtual void Herwig::ThreeMesonCurrentBase::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

◆ decayMode()

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

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

Checks the mesons against the list.

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

◆ operator=()

ThreeMesonCurrentBase & Herwig::ThreeMesonCurrentBase::operator= ( const ThreeMesonCurrentBase )
privatedelete

The assignment operator is private and must never be called.

In fact, it should not even be implemented.

◆ particles()

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

The particles produced by the current.

This returns the mesons for the mode.

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.

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