Use userhooks to veto PYTHIA emissions above the POWHEG scale. More...

#include <PowhegHooks.h>

Inheritance diagram for PowhegHooks:

Public Member Functions
	PowhegHooks ()
	Constructors and destructor.

	PowhegHooks (Pythia , Settings , Logger *)

bool	initAfterBeams ()
	Initialize settings, detailing merging strategy to use.

double	pT (const Event &e, int RadAfterBranch, int EmtAfterBranch, int RecAfterBranch, bool FSR)
	Top-level wrapper for shower pTs. More...

double	pTpythia (const Event &e, int RadAfterBranch, int EmtAfterBranch, int RecAfterBranch, bool FSR)

double	pTvincia (const Event &event, int i1, int i3, int i2)

double	pTdire (const Event &event, int iRad, int iEmt, int iRec)

double	pTpowheg (const Event &e, int i, int j, bool FSR)
	Compute the POWHEG pT separation between i and j. More...

double	pTcalc (const Event &e, int i, int j, int k, int r, int xSRin)

bool	canVetoMPIStep ()

int	numberVetoMPIStep ()
	Up to how many MPI steps should be checked.

bool	doVetoMPIStep (int nMPI, const Event &e)

bool	canVetoISREmission ()
	ISR veto.

bool	doVetoISREmission (int, const Event &e, int iSys)

bool	canVetoFSREmission ()
	FSR veto.

bool	doVetoFSREmission (int, const Event &e, int iSys, bool)

bool	canVetoMPIEmission ()
	MPI veto.

bool	doVetoMPIEmission (int, const Event &e)

int	getNISRveto ()
	Functions to return information.

int	getNFSRveto ()

Public Member Functions inherited from UserHooks
virtual	~UserHooks ()
	Destructor.

virtual bool	canModifySigma ()
	Possibility to modify cross section of process.

virtual double	multiplySigmaBy (const SigmaProcess sigmaProcessPtr, const PhaseSpace phaseSpacePtr, bool inEvent)
	Multiplicative factor modifying the cross section of a hard process. More...

virtual bool	canBiasSelection ()
	Possibility to bias selection of events, compensated by a weight.

virtual double	biasSelectionBy (const SigmaProcess sigmaProcessPtr, const PhaseSpace phaseSpacePtr, bool inEvent)
	Multiplicative factor in the phase space selection of a hard process. More...

virtual double	biasedSelectionWeight ()
	Event weight to compensate for selection weight above.

virtual bool	canVetoProcessLevel ()
	Possibility to veto event after process-level selection.

virtual bool	doVetoProcessLevel (Event &)

virtual bool	canSetLowEnergySigma (int, int) const

virtual double	doSetLowEnergySigma (int, int, double, double, double) const

virtual bool	canVetoResonanceDecays ()
	Possibility to veto resonance decay chain.

virtual bool	doVetoResonanceDecays (Event &)

virtual bool	canVetoPT ()

virtual double	scaleVetoPT ()
	Transverse-momentum scale for veto test.

virtual bool	doVetoPT (int, const Event &)

virtual bool	canVetoStep ()

virtual int	numberVetoStep ()
	Up to how many ISR + FSR steps of hardest interaction should be checked.

virtual bool	doVetoStep (int, int, int, const Event &)

virtual bool	canVetoPartonLevelEarly ()

virtual bool	doVetoPartonLevelEarly (const Event &)

virtual bool	retryPartonLevel ()

virtual bool	canVetoPartonLevel ()
	Possibility to veto event after parton-level selection.

virtual bool	doVetoPartonLevel (const Event &)

virtual bool	canSetResonanceScale ()
	Possibility to set initial scale in TimeShower for resonance decay.

virtual double	scaleResonance (int, const Event &)

virtual bool	canReconnectResonanceSystems ()
	Possibility to reconnect colours from resonance decay systems.

virtual bool	doReconnectResonanceSystems (int, Event &)

virtual bool	canChangeFragPar ()
	Can change fragmentation parameters.

virtual void	setStringEnds (const StringEnd , const StringEnd , vector< int >)

virtual bool	doChangeFragPar (StringFlav , StringZ , StringPT , int, double, vector< int >, const StringEnd )

virtual bool	doVetoFragmentation (Particle, const StringEnd *)

virtual bool	doVetoFragmentation (Particle, Particle, const StringEnd , const StringEnd )

virtual bool	canVetoAfterHadronization ()

virtual bool	doVetoAfterHadronization (const Event &)
	Do the actual veto after hadronization.

virtual bool	canSetImpactParameter () const
	Can set the overall impact parameter for the MPI treatment.

virtual double	doSetImpactParameter ()
	Set the overall impact parameter for the MPI treatment.

virtual bool	onEndHadronLevel (HadronLevel &, Event &)
	Custom processing at the end of HadronLevel::next.

Public Member Functions inherited from PhysicsBase
void	initInfoPtr (Info &infoPtrIn)
	This function is called from above for physics objects used in a run. More...

virtual	~PhysicsBase ()
	Empty virtual destructor.

bool	flag (string key) const
	Shorthand to read settings values.

int	mode (string key) const

double	parm (string key) const

string	word (string key) const

vector< bool >	fvec (string key) const

vector< int >	mvec (string key) const

vector< double >	pvec (string key) const

vector< string >	wvec (string key) const

Additional Inherited Members
Public Types inherited from PhysicsBase
enum	Status { INCOMPLETE = -1, COMPLETE = 0, CONSTRUCTOR_FAILED, INIT_FAILED, LHEF_END, LOWENERGY_FAILED, PROCESSLEVEL_FAILED, PROCESSLEVEL_USERVETO, MERGING_FAILED, PARTONLEVEL_FAILED, PARTONLEVEL_USERVETO, HADRONLEVEL_FAILED, CHECK_FAILED, OTHER_UNPHYSICAL, HEAVYION_FAILED, HADRONLEVEL_USERVETO }
	Enumerate the different status codes the event generation can have.

Protected Member Functions inherited from UserHooks
	UserHooks ()
	Constructor.

virtual void	onInitInfoPtr () override
	After initInfoPtr, initialize workEvent. More...

void	omitResonanceDecays (const Event &process, bool finalOnly=false)
	omitResonanceDecays omits resonance decay chains from process record. More...

void	subEvent (const Event &event, bool isHardest=true)
	subEvent extracts currently resolved partons in the hard process. More...

Protected Member Functions inherited from PhysicsBase
	PhysicsBase ()
	Default constructor.

virtual void	onBeginEvent ()
	This function is called in the very beginning of each Pythia::next call.

virtual void	onEndEvent (Status)

virtual void	onStat ()
	This function is called from the Pythia::stat() call.

void	registerSubObject (PhysicsBase &pb)
	Register a sub object that should have its information in sync with this.

Protected Attributes inherited from UserHooks
Event	workEvent = {}
	Have one event object around as work area.

double	selBias = 1.
	User-imposed selection bias.

double	enhancedEventWeight = {}
	Bookkept quantities for boosted event weights.

double	pTEnhanced = {}

double	wtEnhanced = {}

Protected Attributes inherited from PhysicsBase
Info *	infoPtr = {}

Settings *	settingsPtr = {}
	Pointer to the settings database.

ParticleData *	particleDataPtr = {}
	Pointer to the particle data table.

Logger *	loggerPtr = {}
	Pointer to logger.

HadronWidths *	hadronWidthsPtr = {}
	Pointer to the hadron widths data table.

Rndm *	rndmPtr = {}
	Pointer to the random number generator.

CoupSM *	coupSMPtr = {}
	Pointers to SM and SUSY couplings.

CoupSUSY *	coupSUSYPtr = {}

BeamSetup *	beamSetupPtr = {}

BeamParticle *	beamAPtr = {}

BeamParticle *	beamBPtr = {}

BeamParticle *	beamPomAPtr = {}

BeamParticle *	beamPomBPtr = {}

BeamParticle *	beamGamAPtr = {}

BeamParticle *	beamGamBPtr = {}

BeamParticle *	beamVMDAPtr = {}

BeamParticle *	beamVMDBPtr = {}

PartonSystems *	partonSystemsPtr = {}
	Pointer to information on subcollision parton locations.

SigmaTotal *	sigmaTotPtr = {}
	Pointers to the total/elastic/diffractive cross sections.

SigmaCombined *	sigmaCmbPtr = {}

set< PhysicsBase * >	subObjects

UserHooksPtr	userHooksPtr

Detailed Description

Use userhooks to veto PYTHIA emissions above the POWHEG scale.

Member Function Documentation

bool canVetoMPIStep ( )

inlinevirtual

Extraction of pThard based on the incoming event. Assume that all the final-state particles are in a continuous block at the end of the event and the final entry is the POWHEG emission. If there is no POWHEG emission, then pThard is set to SCALUP.

Reimplemented from UserHooks.

bool doVetoFSREmission	(	int	,
		const Event &	,
		int	,
		bool
	)

inlinevirtual

Decide whether to veto current emission or not, based on event record. Usage: doVetoFSREmission( sizeOld, event, iSys, inResonance) where sizeOld is size of event record before current emission-to-be-scrutinized was added, iSys is the system of the radiation (according to PartonSystems), and inResonance is true if the emission takes place in a resonance decay.

Must be radiation from the hard system.

If we already have accepted 'vetoCount' emissions in a row, do nothing.

Pythia radiator (before and after), emitted and recoiler (after).

Pythia or Dire.

Vincia.

Behaviour based on pTemtMode: 0 - pT of emitted w.r.t. radiator before 1 - min(pT of emitted w.r.t. all incoming/outgoing) 2 - min(pT of all outgoing w.r.t. all incoming/outgoing)

When pTemtMode is 0 or 1, iEmt has been selected.

Which parton is emitted, based on emittedMode: 0 - Pythia definition of emitted 1 - Pythia definition of radiated after emission 2 - Random selection of emitted or radiated after emission 3 - Try both emitted and radiated after emission

For emittedMode == 3, have tried iRadAft, now try iEmt

If pTemtMode is 2, then try all final-state partons as emitted

If a Born configuration, and a photon, and QEDvetoMode=2, then don't veto photons, W's or Z's harder than pThard

Veto if pTemt > pThard

Don't veto ANY emissions afterwards

Else mark that an emission has been accepted and continue

Reimplemented from UserHooks.

bool doVetoISREmission	(	int	,
		const Event &	,
		int
	)

inlinevirtual

Decide whether to veto current emission or not, based on event record. Usage: doVetoISREmission( sizeOld, event, iSys) where sizeOld is size of event record before current emission-to-be-scrutinized was added, and iSys is the system of the radiation (according to PartonSystems).

Must be radiation from the hard system

If we already have accepted 'vetoCount' emissions in a row, do nothing

Pythia radiator after, emitted and recoiler after.

Pythia.

Vincia.

Dire.

pTemtMode == 0: pT of emitted w.r.t. radiator pTemtMode == 1: min(pT of emitted w.r.t. all incoming/outgoing) pTemtMode == 2: min(pT of all outgoing w.r.t. all incoming/outgoing)

If a Born configuration, and a photon, and QEDvetoMode=2, then don't veto photons, W, or Z harder than pThard.

Veto if pTemt > pThard.

Don't veto ANY emissions afterwards.

Else mark that an emission has been accepted and continue.

Reimplemented from UserHooks.

bool doVetoMPIEmission	(	int	,
		const Event &
	)

inlinevirtual

Decide whether to veto an MPI based on event record. Usage: doVetoMPIEmission( sizeOld, event) where sizeOld is size of event record before the current MPI.

Reimplemented from UserHooks.

bool doVetoMPIStep	(	int	,
		const Event &
	)

inlinevirtual

Decide whether to veto current event or not, based on event record. Usage: doVetoMPIStep( nMPI, event), where nMPI is number of MPI's so far.

Extra check on nMPI

When nFinal is set, be strict about comparing the number of final-state particles with expectation from Born and single-real emission states. (Note: the default from 8.309 onwards is nFinal = -1).

Find if there is a POWHEG emission. Go backwards through the event record until there is a non-final particle. Also sum pT and find pT_1 for possible MPI vetoing

Extra check that we have the correct final state

Flag if POWHEG radiation present and index

If nFinal == -1, then go through the event and extract only the information on the emission and its pT, but do not enforce strict comparisons of final state multiplicity.

Flag whether POWHEG radiation is present, and save index of emission.

If there is no radiation or if pThardMode is 0 then set pThard = SCALUP.

If pThardMode is 1 then the pT of the POWHEG emission is checked against all other incoming and outgoing partons, with the minimal value taken.

If pThardMode is 2, then the pT of all final-state partons is checked against all other incoming and outgoing partons, with the minimal value taken.

Find MPI veto pT if necessary.

Initialise other variables.

Do not veto the event

Reimplemented from UserHooks.

double pT	(	const Event &	e,
		int	RadAfterBranch,
		int	EmtAfterBranch,
		int	RecAfterBranch,
		bool	FSR
	)

inline

Top-level wrapper for shower pTs.

Routines to calculate the pT (according to pTdefMode) in a branching: ISR: i (radiator after) -> j (emitted after) k (radiator before) FSR: i (radiator before) -> j (emitted after) k (radiator after) For the Pythia pT definitions, a recoiler (after) must be specified.

VINCIA pT definition.

DIRE pT definition.

double pTcalc	(	const Event &	e,
		int	i,
		int	j,
		int	k,
		int	r,
		int	xSRin
	)

inline

Calculate pT for a splitting based on pTdefMode. If j is -1, all final-state partons are tried. If i, k, r and xSR are -1, then all incoming and outgoing partons are tried. xSR set to 0 means ISR, while xSR set to 1 means FSR.

Loop over ISR and FSR if necessary

FSR flag

If all necessary arguments have been given, then directly calculate. POWHEG ISR and FSR, need i and j.

Pythia ISR, need i, j and r.

Pythia FSR, need k, j and r.

Otherwise need to try all possible combinations.

Start by finding incoming legs to the hard system after branching (radiator after branching, i for ISR). Use partonSystemsPtr to find incoming just prior to the branching and track mothers.

If we do not have j, then try all final-state partons.

Final-state only.

Exclude photons (and W/Z!)

POWHEG.

ISR - only done once as just kinematical pT.

FSR - try all outgoing partons from system before branching as i. Note that for the hard system, there is no "before branching" information.

i != jNow and no carbon copies

Exclude photons (and W/Z!)

for (iMem)

if (!FSR)

Pythia.

ISR - other incoming as recoiler.

FSR - try all final-state coloured partons as radiator after emission (k).

For this kNow, need to have a recoiler. Try two incoming.

Try all other outgoing.

for (rNow)

for (kNow)

if (!FSR)

if (pTdefMode)

for (j)

for (xSR)

double pTdire	(	const Event &	event,
		int	iRad,
		int	iEmt,
		int	iRec
	)

inline

Compute the Dire pT as in DireTimes::pT2_FF, DireTimes::pT2_FI, DireSpace::pT2_IF, DireSpace::pT2_II.

Shorthands.

Calculate pT2 depending on dipole configuration.

FF – copied from DireTimes::pT2_FF.

FI.

IF.

II.

Sanity check.

Return pT.

double pTpowheg	(	const Event &	e,
		int	i,
		int	j,
		bool	FSR
	)

inline

Compute the POWHEG pT separation between i and j.

pT value for FSR and ISR

POWHEG d_ij (in CM frame). Note that the incoming beams have not been updated in the parton systems pointer yet (i.e. prior to any potential recoil).

POWHEG pT_ISR is just kinematic pT

Check result.

double pTpythia	(	const Event &	e,
		int	RadAfterBranch,
		int	EmtAfterBranch,
		int	RecAfterBranch,
		bool	FSR
	)

inline

Compute the Pythia pT separation. Based on pTLund function in History.cc and identical to pTevol.

Convenient shorthands for later

Calculate virtuality of splitting

Mass term of radiator

z values for FSR and ISR

Construct 2 -> 3 variables

Construct dipoles before/after splitting

Virtuality with correct sign

Can get negative pT for massive splittings.

Return pT

double pTvincia	(	const Event &	event,
		int	i1,
		int	i3,
		int	i2
	)

inline

Compute the Vincia pT as in Eq. (2.63)-(2.66) in arXiv:2003.00702. Branching is assumed to be {13} {23} -> 1 3 2.

Shorthands.

Fetch mothers of 1 and 2.

Invariants defined as in Eq. (5) in arXiv:2008.09468.

Normalisation as in Eq. (6) in arXiv:2008.09468.

FF.

RF or IF.

FR or FI.

II.

Calculate pT2 as in Eq. (5) in arXiv:2008.09468.

Sanity check.

Return pT.

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

include/Pythia8Plugins/PowhegHooks.h

Public Member Functions

Additional Inherited Members

Detailed Description

Member Function Documentation