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)
	RIVET_DEFAULT_PROJ_CLONE (Thrust)
	Clone on the heap.
virtual unique_ptr< Projection >	clone () const =0
	Clone on the heap.
virtual std::string	name () const
	Get the name of the projection.
bool	valid () const
	Get the state of the projetion.
bool	failed () const
	Get the state of the projetion.
void	markAsOwned () const
	Mark this object as owned by a proj-handler.

double	thrust () const
double	thrustMajor () const
	The thrust major scalar, \( M \), (thrust along thrust major axis).
double	thrustMinor () const
	The thrust minor scalar, \( m \), (thrust along thrust minor axis).
double	oblateness () const
	The oblateness, \( O = M - m \) .

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.
Projection operation and comparison
bool	before (const Projection &p) const
Projection "getting" functions
std::set< ConstProjectionPtr >	getProjections () const
	Get the contained projections, including recursion.
std::set< ConstProjectionPtr >	getImmediateChildProjections () const
	Get the contained projections, excluding 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
const Projection &	getProjection (const std::string &name) const
template<typename PROJ>
const PROJ &	get (const std::string &name) const
template<typename PROJ>
const PROJ &	getProjectionFromDeclQueue (const std::string name) const
Projection applying functions
template<typename PROJ = Projection>
std::enable_if_t< std::is_base_of< Projection, PROJ >::value, const PROJ & >	apply (const Event &evt, const Projection &proj) const
	Apply the supplied projection on event evt.
template<typename PROJ = Projection>
std::enable_if_t< std::is_base_of< Projection, PROJ >::value, const PROJ & >	apply (const Event &evt, const PROJ &proj) const
	Apply the supplied projection on event evt (user-facing alias).
template<typename PROJ = Projection>
std::enable_if_t< std::is_base_of< Projection, PROJ >::value, const PROJ & >	apply (const Event &evt, const std::string &name) const
	Apply the supplied projection on event evt (user-facing alias).
template<typename PROJ = Projection>
std::enable_if_t< std::is_base_of< Projection, PROJ >::value, const PROJ & >	apply (const std::string &name, const Event &evt) const
	Apply the supplied projection on event evt (convenience arg-reordering alias).

Protected Member Functions
void	project (const Event &e)
	Perform the projection on the Event.
CmpState	compare (const Projection &p) const
	Compare projections.
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.
void	fail ()
	Set the projection in an unvalid state.
Cmp< Projection >	mkNamedPCmp (const Projection &otherparent, const std::string &pname) const
Cmp< Projection >	mkPCmp (const Projection &otherparent, const std::string &pname) const
ProjectionHandler &	getProjHandler () const
	Get a reference to the ProjectionHandler for this thread.
void	setProjectionHandler (ProjectionHandler &projectionHandler) const
Projection registration functions
template<typename PROJ>
const PROJ &	declare (const PROJ &proj, const std::string &name) const
	Register a contained projection (user-facing version).
template<typename PROJ>
const PROJ &	declare (const std::string &name, const PROJ &proj) const
	Register a contained projection (user-facing, arg-reordered version).

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

◆ apply()

template<typename PROJ = Projection>

std::enable_if_t< std::is_base_of< Projection, PROJ >::value, const PROJ & > Rivet::ProjectionApplier::apply	(	const Event &	evt,
		const Projection &	proj ) const

inlineinherited

Apply the supplied projection on event evt.

Apply the supplied projection on event evt (user-facing alias).

◆ axis1()

const Vector3 & Rivet::Thrust::axis1 ( ) const

inlinevirtual

AxesDefinition axis accessors.

Implements Rivet::AxesDefinition.

References thrustAxis().

◆ axis2()

const Vector3 & Rivet::Thrust::axis2 ( ) const

inlinevirtual

The 2nd most significant ("major") axis.

Implements Rivet::AxesDefinition.

References thrustMajorAxis().

◆ axis3()

const Vector3 & Rivet::Thrust::axis3 ( ) const

inlinevirtual

The least significant ("minor") axis.

Implements Rivet::AxesDefinition.

References thrustMinorAxis().

◆ before()

bool Rivet::Projection::before ( const Projection & p ) const

inherited

Determine whether this object should be ordered before the object p given as argument. If p is of a different class than this, the before() function of the corresponding type_info objects is used. Otherwise, if the objects are of the same class, the virtual compare(const Projection &) will be returned.

References Projection(), and Rivet::Kin::p().