Base class for parton distribution functions. More...

#include <PartonDistributions.h>

Inheritance diagram for PDF:

Classes
struct	PDFEnvelope
	Error envelope from PDF uncertainty. More...

Public Member Functions
	PDF (int idBeamIn=2212)
	Constructor.

virtual	~PDF ()
	Virtual destructor.

virtual bool	init (int, string, int, Logger *)

bool	isSetup ()
	Confirm that PDF has been set up (important for LHAPDF and H1 Pomeron).

virtual void	setBeamID (int idBeamIn)
	Switch to new beam particle identities; for similar hadrons only.

void	resetValenceContent ()
	Set valence content. More...

void	setValenceContent (int idVal1In, int idVal2In, int idVal3In)

virtual void	setExtrapolate (bool)
	Allow extrapolation beyond boundaries. This is optional.

double	xf (int id, double x, double Q2)
	Read out parton density. More...

double	xfVal (int id, double x, double Q2)
	Read out valence and sea part of parton densities. More...

double	xfSea (int id, double x, double Q2)
	Only sea part of parton densities. More...

virtual bool	insideBounds (double, double)
	Check whether x and Q2 values fall inside the fit bounds (LHAPDF6 only).

virtual double	alphaS (double)
	Access the running alpha_s of a PDF set (LHAPDF6 only).

virtual double	mQuarkPDF (int)
	Return quark masses used in the PDF fit (LHAPDF6 only).

virtual int	nMembers ()
	Return number of members of this PDF family (LHAPDF6 only).

virtual void	calcPDFEnvelope (int, double, double, int)
	Calculate PDF envelope.

virtual void	calcPDFEnvelope (pair< int, int >, pair< double, double >, double, int)

virtual PDFEnvelope	getPDFEnvelope ()

virtual double	gammaPDFxDependence (int, double)
	Approximate photon PDFs by decoupling the scale and x-dependence.

virtual double	gammaPDFRefScale (int)
	Provide the reference scale for logarithmic Q^2 evolution for photons.

virtual int	sampleGammaValFlavor (double)
	Sample the valence content for photons.

virtual double	xfIntegratedTotal (double)
	The total x-integrated PDFs. Relevant for MPIs with photon beams.

virtual double	xGamma ()
	Return the sampled value for x_gamma.

virtual void	xPom (double=-1.0)
	Keep track of pomeron momentum fraction.

virtual double	xfFlux (int, double, double)
	Return accurate and approximated photon fluxes and PDFs.

virtual double	xfApprox (int, double, double)

virtual double	xfGamma (int, double, double)

virtual double	intFluxApprox ()

virtual bool	hasApproxGammaFlux ()

virtual double	getXmin ()
	Return the kinematical limits and sample Q2 and x.

virtual double	getXhadr ()

virtual double	sampleXgamma (double)

virtual double	sampleQ2gamma (double)

virtual double	fluxQ2dependence (double)

virtual double	xfMax (int id, double x, double Q2)
	Normal PDFs unless gamma inside lepton -> an overestimate for sampling.

virtual double	xfSame (int id, double x, double Q2)
	Normal PDFs unless gamma inside lepton -> Do not sample x_gamma.

virtual void	setVMDscale (double=1.)
	Allow for new scaling factor for VMD PDFs.

bool	sSymmetric () const
	Return if s/sbar, c/cbar, and b/bbar PDFs are symmetric.

bool	cSymmetric () const

bool	bSymmetric () const

void	sSymmetric (bool sSymmetricIn)
	Set s/sbar, c/cbar, and b/bbar PDFs symmetric.

void	cSymmetric (bool cSymmetricIn)

void	bSymmetric (bool bSymmetricIn)

Protected Member Functions
virtual void	xfUpdate (int id, double x, double Q2)=0
	Update parton densities.

void	printErr (string loc, string errMsg, Logger *loggerPtr=nullptr)
	Small routine for error printout, depending on loggerPtr existing or not.

double	xfRaw (int id) const
	Get the raw stored value for the quark variable corresponding to the id. More...

bool	isValence (int id) const
	Check whether the specified id is a valence quark.

Protected Attributes
int	idBeam
	Store relevant quantities.

int	idBeamAbs

int	idSav

int	idVal1

int	idVal2

int	idVal3

double	xSav

double	Q2Sav

double	xu
	Stored quantities.

double	xd

double	xs

double	xubar

double	xdbar

double	xsbar

double	xc

double	xb

double	xcbar

double	xbbar

double	xg

double	xlepton

double	xgamma

bool	isSet

bool	isInit

int	beamType

bool	hasGammaInLepton
	True if a photon beam inside a lepton beam, otherwise set false.

bool	sSymmetricSave = false
	Whether to treat flavoured PDFs as symmetric, for efficiency.

bool	cSymmetricSave = true

bool	bSymmetricSave = true

Detailed Description

Base class for parton distribution functions.

Member Function Documentation

virtual bool init	(	int	,
		string	,
		int	,
		Logger *
	)

inlinevirtual

Perform additional initialization (LHPADF only). Arguments are: int idBeamIn, string setName, int member, Logger* loggerPtr

Reimplemented in LHAPDF5, and LHAPDF6.

void resetValenceContent ( )

Set valence content.

Base class for parton distribution functions.

Set valence content to the default for the current beam.

Gluon has no valence.

Photons can fluctuate. 22 indicates that valence has not been set.

Lepton and neutrino.

Pomeron is treated as pi0-like.

Nuclear beams.

Generic hadron beams.

Decompose default valence content.

For mesons, one quark is an antiquark.

Flip signs for antiparticle beam.

Set valence content.

Determine and store beam type. Diagonal meson special cases.

pi0-like are different from other diagonal mesons.

K_S,L special case.

For other cases, beamType tells about isospin symmetries.

Count number of u/d quarks.

double xf	(	int	id,
		double	x,
		double	Q2
	)

Read out parton density.

Standard parton densities.

Need to update if flavour, x or Q2 changed. Use idSav = 9 to indicate that ALL flavours are up-to-date. Assume that flavour and antiflavour always updated simultaneously.

Photon/gluon content is always handled the same way.

Photon beam, always the full PDFs.

Lepton or neutrino beam, only charged leptons may emit photons.

Nuclear beam.

Special treatment for pi0-like mesons, based on pi+ content.

For other diagonal mesons, q = sea + valence; qbar = sea.

Special treatment of K_S/K_L, based on K+ content.

For other hadrons, handle u/d through isospin symmetry.

No rearrangement necessary (e.g. p, Sigma+, Xi0, Omega-, pi+).

Switch u <-> d (e.g. n, Sigma-, Xi-, K0, D+, B0).

Use average of u and d (e.g. Lambda0, Sigma0).

Delta++: move d valence into u.

Delta-: as Delta++, but switch u <-> d.

s/c/b is always the same.

None of the above cases work, e.g. id is not a valid particle.

double xfRaw ( int id ) const

protected

Get the raw stored value for the quark variable corresponding to the id.

Get the raw value for the quark variable corresponding to the id.

double xfSea	(	int	id,
		double	x,
		double	Q2
	)

Only sea part of parton densities.

Update configuration if necessary.

Gluon is always sea.

Photon beam.

If a valence parton return only the sea part. Otherwise return the total PDF.

Except in pointlike photon beams, gamma is always sea.

The only sea in leptons are photons.

Nuclear PDFs are not yet handled.

Special treatment for pi0-like mesons, based on pi+ content.

For other diagonal mesons, q = sea + valence; qbar = sea.

Otherwise, if q is valence xor beam is an antiparticle, flip sign.

Special treatment of K_S/K_L, based on K+ content.

For other hadrons, handle u/d through isospin symmetry.

No rearrangement necessary (e.g. p, Sigma+, Xi0, Omega-, pi+).

Switch u <-> d (e.g. n, Delta-, Sigma-, Xi-, K0, D+, B0).

Use average of u and d (e.g. Lambda0, Sigma0).

For Delta++, always use qbar value.

s/c/b is always the same.

None of the above cases work, e.g. id is not a valid particle.

double xfVal	(	int	id,
		double	x,
		double	Q2
	)

Read out valence and sea part of parton densities.

Only valence part of parton densities.

Check parton is valence.

Update configuration if necessary.

Photon beam, return non-zero valence content only if flavour set.

Photon/gluon content is never valence.

For lepton and neutrino beams, the valence is the lepton content itself.

Nuclear PDFs are not yet defined.

Special treatment for pi0-like mesons, based on pi+ content.

For other diagonal mesons, q = sea + valence; qbar = sea.

Special treatment of K_S/K_L, based on K+ content.

For other hadrons, handle u/d through isospin symmetry.

No rearrangement necessary (e.g. p, Sigma+, Xi0, Omega-, pi+).

Switch u <-> d (e.g. n, Sigma-, Xi-, K0, D+, B0).

Use average of u and d (e.g. Lambda0, Sigma0).

Delta++/-: take both d and u (we already checked that it's valence).

s/c/b is always the same.

None of the above cases work, e.g. id is not a valid particle.

Member Data Documentation

int beamType

protected

For hadrons, beamType defines special cases and determines how to handle isospin symmetries. 1: no rearrangement (e.g. p, Sigma+, Omega-, pi+) -1: switch u <-> d (e.g. n, Sigma-, Xi-, K0) 0: take average of u and d (e.g. Sigma0, Lambda0) 2/-2: Delta++/Delta- 111: pi0-like special case (pi0, rho0, omega, etc.) 221: Other diagonal meson cases (eta, eta', phi, J/psi, Upsilon, etc.) 130: K_S,L special cases

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

include/Pythia8/PartonDistributions.h
src/PartonDistributions.cc

Classes

Public Member Functions

Protected Member Functions

Protected Attributes

Detailed Description

Member Function Documentation

Member Data Documentation