Rivet::Sphericity Class Referenceabstract Calculate the sphericity event shape. More...
Inheritance diagram for Rivet::Sphericity:
Detailed DescriptionCalculate the sphericity event shape. The sphericity tensor (or quadratic momentum tensor) is defined as \[ S^{\alpha \beta} = \frac{\sum_i p_i^\alpha p_i^\beta}{\sum_i |\mathbf{p}_i|^2} \] , where the Greek indices are spatial components and the Latin indices are used for sums over particles. From this, the sphericity, aplanarity and planarity can be calculated by combinations of eigenvalues. Defining the three eigenvalues \( \lambda_1 \ge \lambda_2 \ge \lambda_3 \), with \( \lambda_1 + \lambda_2 + \lambda_3 = 1 \), the sphericity is \[ S = \frac{3}{2} (\lambda_2 + \lambda_3) \] The aplanarity is \( A = \frac{3}{2}\lambda_3 \) and the planarity is \( P = \frac{2}{3}(S-2A) = \lambda_2 - \lambda_3 \). The eigenvectors define a set of spatial axes comparable with the thrust axes, but more sensitive to high momentum particles due to the quadratic sensitivity of the tensor to the particle momenta. Since the sphericity is quadratic in the particle momenta, it is not an infrared safe observable in perturbative QCD. This can be fixed by adding a regularizing power of \(r\) to the definition: \[ S^{\alpha \beta} = \frac{\sum_i |\mathbf{p}_i|^{r-2} p_i^\alpha p_i^\beta} {\sum_i |\mathbf{p}_i|^r} \] \(r\) is available as a constructor argument on this class and will be taken into account by the Cmp<Projection> operation, so a single analysis can use several sphericity projections with different \(r\) values without fear of a clash. Member Function Documentation◆ addPdgIdPair()
Add a colliding beam pair.
◆ applyProjection() [1/3]
template<typename PROJ = Projection>
Apply the supplied projection on event evt.
◆ applyProjection() [2/3]
template<typename PROJ = Projection>
Apply the supplied projection on event evt.
◆ applyProjection() [3/3]
template<typename PROJ = Projection>
Apply the named projection on event evt.
References Rivet::ProjectionApplier::name(). ◆ axis1()
Axis accessors, in decreasing order of significance. The main axis. Implements Rivet::AxesDefinition. References sphericityAxis(). ◆ axis2()
The 2nd most significant ("major") axis. Implements Rivet::AxesDefinition. References sphericityMajorAxis(). ◆ axis3()
The least significant ("minor") axis. Implements Rivet::AxesDefinition. References sphericityMinorAxis(). ◆ beamPairs()
Return the allowed beam pairs on which this projection can operate, not including recursion. Derived classes should ensure that all contained projections are registered in the _projections set for the beam constraint chaining to work.
◆ before()
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. ◆ calc()
Manually calculate the sphericity, without engaging the caching system. This one actually does the calculation ◆ clone()
Clone on the heap. Implements Rivet::Projection. ◆ compare()
Compare with other projections. Implements Rivet::Projection. ◆ declare() [1/2]
template<typename PROJ >
Register a contained projection (user-facing version)
References Rivet::ProjectionApplier::declareProjection(), and Rivet::ProjectionApplier::name(). Referenced by Rivet::CentralEtHCM::CentralEtHCM(), Rivet::CentralityEstimator::CentralityEstimator(), Rivet::ChargedLeptons::ChargedLeptons(), Rivet::ALICE::CLMultiplicity< INNER >::CLMultiplicity(), Rivet::DISDiffHadron::DISDiffHadron(), Rivet::DISFinalState::DISFinalState(), Rivet::DISKinematics::DISKinematics(), Rivet::DISLepton::DISLepton(), Rivet::GammaGammaFinalState::GammaGammaFinalState(), Rivet::GammaGammaKinematics::GammaGammaKinematics(), Rivet::GammaGammaLeptons::GammaGammaLeptons(), Rivet::GeneratedCentrality::GeneratedCentrality(), Rivet::HadronicFinalState::HadronicFinalState(), Rivet::HeavyHadrons::HeavyHadrons(), Rivet::Hemispheres::Hemispheres(), Rivet::InvisibleFinalState::InvisibleFinalState(), Rivet::LeadingParticlesFinalState::LeadingParticlesFinalState(), Rivet::LossyFinalState< FILTER >::LossyFinalState(), Rivet::MC_pPbMinBiasTrigger::MC_pPbMinBiasTrigger(), Rivet::MC_SumETFwdPbCentrality::MC_SumETFwdPbCentrality(), Rivet::ATLAS::MinBiasTrigger::MinBiasTrigger(), Rivet::MissingMomentum::MissingMomentum(), Rivet::NeutralFinalState::NeutralFinalState(), Rivet::NonHadronicFinalState::NonHadronicFinalState(), Rivet::ParisiTensor::ParisiTensor(), Rivet::PercentileProjection::PercentileProjection(), Rivet::PrimaryHadrons::PrimaryHadrons(), Rivet::SmearedJets::SmearedJets(), Rivet::SmearedMET::SmearedMET(), Rivet::SmearedParticles::SmearedParticles(), Rivet::Spherocity::Spherocity(), Rivet::ATLAS::SumET_PB_Centrality::SumET_PB_Centrality(), Rivet::ATLAS::SumET_PBPB_Centrality::SumET_PBPB_Centrality(), Rivet::TauFinder::TauFinder(), Rivet::TriggerCDFRun0Run1::TriggerCDFRun0Run1(), Rivet::TriggerCDFRun2::TriggerCDFRun2(), Rivet::UndressBeamLeptons::UndressBeamLeptons(), Rivet::ALICE::V0AndTrigger::V0AndTrigger(), Rivet::ALICE::V0Trigger< MODE >::V0Trigger(), Rivet::VetoedFinalState::VetoedFinalState(), Rivet::VisibleFinalState::VisibleFinalState(), Rivet::CentralityProjection::add(), Rivet::VetoedFinalState::addVetoOnThisFinalState(), and Rivet::CentralityBinner< T, MDist >::setProjection(). ◆ declare() [2/2]
template<typename PROJ >
Register a contained projection (user-facing, arg-reordered version)
References Rivet::ProjectionApplier::declareProjection(), and Rivet::ProjectionApplier::name(). ◆ declareProjection()
template<typename PROJ >
Register a contained projection. The type of the argument is used to instantiate a new projection internally: this new object is applied to events rather than the argument object. Hence you are advised to only use locally-scoped Projection objects in your Projection and Analysis constructors, and to avoid polymorphism (e.g. handling
References Rivet::ProjectionApplier::name(). Referenced by Rivet::ProjectionApplier::declare(). ◆ get()
template<typename PROJ >
Get the named projection, specifying return type via a template argument (user-facing alias).
References Rivet::ProjectionApplier::name(). ◆ getProjection() [1/2]
template<typename PROJ >
Get the named projection, specifying return type via a template argument.
References Rivet::ProjectionHandler::getProjection(), Rivet::ProjectionApplier::getProjHandler(), Rivet::ProjectionApplier::name(), and Rivet::Kin::p(). Referenced by Rivet::CentralityProjection::compare(), and Rivet::pcmp(). ◆ getProjection() [2/2]
Get the named projection (non-templated, so returns as a reference to a Projection base class). References Rivet::ProjectionHandler::getProjection(), Rivet::ProjectionApplier::getProjHandler(), and Rivet::ProjectionApplier::name(). ◆ mkNamedPCmp()
Shortcut to make a named Cmp<Projection> comparison with the Referenced by Rivet::MC_SumETFwdPbCentrality::compare(), Rivet::MC_pPbMinBiasTrigger::compare(), Rivet::BeamThrust::compare(), Rivet::CentralEtHCM::compare(), Rivet::DISFinalState::compare(), Rivet::EventMixingBase::compare(), Rivet::FParameter::compare(), Rivet::GammaGammaFinalState::compare(), Rivet::HeavyHadrons::compare(), Rivet::Hemispheres::compare(), Rivet::LossyFinalState< FILTER >::compare(), Rivet::PercentileProjection::compare(), Rivet::Spherocity::compare(), Rivet::Thrust::compare(), Rivet::ATLAS::SumET_PB_Centrality::compare(), Rivet::ATLAS::SumET_PBPB_Centrality::compare(), Rivet::ATLAS::MinBiasTrigger::compare(), Rivet::CentralityEstimator::compare(), Rivet::GeneratedCentrality::compare(), Rivet::STAR_BES_Centrality::compare(), and Rivet::BRAHMSCentrality::compare(). ◆ mkPCmp()
Shortcut to make a named Cmp<Projection> comparison with the
Referenced by Rivet::ALICE::PrimaryParticles::compare(), Rivet::SmearedJets::compare(), Rivet::SmearedMET::compare(), Rivet::SmearedParticles::compare(), and Rivet::Correlators::compare(). ◆ name()
Get the name of the projection. Implements Rivet::ProjectionApplier. Referenced by Rivet::VetoedFinalState::addVetoOnThisFinalState(), Rivet::Projection::getLog(), and Rivet::Projection::setName(). ◆ project()
Perform the projection on the Event. Implements Rivet::Projection. The documentation for this class was generated from the following file:
Generated on Fri May 13 2022 23:02:06 for Rivet by  1.9.4
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