Get the e+ e- thrust basis and the thrust, thrust major and thrust minor scalars. More...

#include <Thrust.hh>

Inheritance diagram for Rivet::Thrust:

Public Member Functions
	Thrust ()
	Constructor.

	Thrust (const FinalState &fsp)

	DEFAULT_RIVET_PROJ_CLONE (Thrust)
	Clone on the heap.


double	thrust () const

double	thrustMajor () const
	The thrust major scalar, , (thrust along thrust major axis).

double	thrustMinor () const
	The thrust minor scalar, , (thrust along thrust minor axis).

double	oblateness () const
	The oblateness, .


const Vector3 &	thrustAxis () const

const Vector3 &	thrustMajorAxis () const
	The thrust major axis (axis of max thrust perpendicular to thrust axis).

const Vector3 &	thrustMinorAxis () const
	The thrust minor axis (axis perpendicular to thrust and thrust major).


const Vector3 &	axis1 () const
	AxesDefinition axis accessors.

const Vector3 &	axis2 () const
	The 2nd most significant ("major") axis.

const Vector3 &	axis3 () const
	The least significant ("minor") axis.

Direct methods
Ways to do the calculation directly, without engaging the caching system
void	calc (const FinalState &fs)
	Manually calculate the thrust, without engaging the caching system.

void	calc (const vector< Particle > &fsparticles)
	Manually calculate the thrust, without engaging the caching system.

void	calc (const vector< FourMomentum > &fsmomenta)
	Manually calculate the thrust, without engaging the caching system.

void	calc (const vector< Vector3 > &threeMomenta)
	Manually calculate the thrust, without engaging the caching system.

Public Member Functions inherited from Rivet::AxesDefinition
virtual	~AxesDefinition ()
	Virtual destructor.

virtual unique_ptr< Projection >	clone () const =0
	Clone on the heap.

Public Member Functions inherited from Rivet::Projection
virtual std::string	name () const
	Get the name of the projection.

	Projection ()
	The default constructor.

virtual	~Projection ()
	The destructor.

bool	before (const Projection &p) const

virtual const std::set< PdgIdPair >	beamPairs () const

Projection &	addPdgIdPair (PdgId beam1, PdgId beam2)

Public Member Functions inherited from Rivet::ProjectionApplier
	ProjectionApplier ()
	Constructor.

void	markAsOwned () const
	Mark this object as owned by a proj-handler.

std::set< ConstProjectionPtr >	getProjections () const
	Get the contained projections, including recursion.

bool	hasProjection (const std::string &name) const
	Does this applier have a projection registered under the name name?

template<typename PROJ >
const PROJ &	getProjection (const std::string &name) const

template<typename PROJ >
const PROJ &	get (const std::string &name) const

const Projection &	getProjection (const std::string &name) const

template<typename PROJ >
const PROJ &	applyProjection (const Event &evt, const Projection &proj) const
	Apply the supplied projection on event evt. More...

template<typename PROJ >
const PROJ &	apply (const Event &evt, const Projection &proj) const

template<typename PROJ >
const PROJ &	applyProjection (const Event &evt, const PROJ &proj) const
	Apply the supplied projection on event evt. More...

template<typename PROJ >
const PROJ &	apply (const Event &evt, const PROJ &proj) const

template<typename PROJ >
const PROJ &	applyProjection (const Event &evt, const std::string &name) const

template<typename PROJ >
const PROJ &	apply (const Event &evt, const std::string &name) const

template<typename PROJ >
const PROJ &	apply (const std::string &name, const Event &evt) const

Protected Member Functions
void	project (const Event &e)
	Perform the projection on the Event.

int	compare (const Projection &p) const
	Compare projections.

Protected Member Functions inherited from Rivet::Projection
Log &	getLog () const
	Get a Log object based on the getName() property of the calling projection object.

void	setName (const std::string &name)
	Used by derived classes to set their name.

Cmp< Projection >	mkNamedPCmp (const Projection &otherparent, const std::string &pname) const

Cmp< Projection >	mkPCmp (const Projection &otherparent, const std::string &pname) const

virtual Projection &	operator= (const Projection &)
	Block Projection copying.

Protected Member Functions inherited from Rivet::ProjectionApplier
Log &	getLog () const

ProjectionHandler &	getProjHandler () const
	Get a reference to the ProjectionHandler for this thread.

template<typename PROJ >
const PROJ &	declareProjection (const PROJ &proj, const std::string &name)
	Register a contained projection. More...

template<typename PROJ >
const PROJ &	declare (const PROJ &proj, const std::string &name)
	Register a contained projection (user-facing version) More...

template<typename PROJ >
const PROJ &	declare (const std::string &name, const PROJ &proj)
	Register a contained projection (user-facing, arg-reordered version) More...

template<typename PROJ >
const PROJ &	addProjection (const PROJ &proj, const std::string &name)
	Register a contained projection (user-facing version) More...

Detailed Description

Get the e+ e- thrust basis and the thrust, thrust major and thrust minor scalars.

Author: Andy Buckley

The scalar (maximum) thrust is defined as

$T = \mathrm{max}_{\vec{n}} \frac{\sum_i \left|\vec{p}_i \cdot \vec{n} \right|}{\sum_i |\vec{p}_i|}$

, with the direction of the unit vector $\vec{n}$ which maximises $ T $ being identified as the thrust axis. The unit vector which maximises the thrust scalar in the plane perpendicular to $\vec{n}$ is the "thrust major" direction, and the vector perpendicular to both the thrust and thrust major directions is the thrust minor. Both the major and minor directions have associated thrust scalars.

Thrust calculations have particularly simple forms for less than 4 particles, and in those cases this projection is computationally minimal. For 4 or more particles, a more general calculation must be carried out, based on the Brandt/Dahmen method from Z. Phys. C1 (1978). While a polynomial improvement on the exponential scaling of the naive method, this algorithm scales asymptotically as $\mathcal{O}\left( n^3 \right)$ . Be aware that the thrust may easily be the most computationally demanding projection in Rivet for large events!

The Rivet implementation of thrust is based heavily on Stefan Gieseke's Herwig++ re-coding of the 'tasso' code from HERWIG.

NB. special case with >= 4 coplanar particles will still fail. NB. Thrust assumes all momenta are in the CoM system: no explicit boost is performed. This can be dealt with by appropriate choice of the supplied FinalState.

Member Function Documentation

◆ thrust()

double Rivet::Thrust::thrust ( ) const

inline

Thrust scalar accessors The thrust scalar, $ T $ , (maximum thrust).

◆ thrustAxis()

const Vector3& Rivet::Thrust::thrustAxis ( ) const

inline

Thrust axis accessors The thrust axis.

Referenced by axis1().

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

include/Rivet/Projections/Thrust.hh
src/Projections/Thrust.cc

Public Member Functions

Protected Member Functions

Detailed Description

Member Function Documentation

◆ thrust()

◆ thrustAxis()