Vertex-fitting convenience functions
7.5.3. Vertex-fitting convenience functions#
Hint
A vertex fit will most likely change the kinematic properties of the decay head (mother) and,
if the option daughtersUpdate
(kFit
) or updateAllDaughters
(treeFit
) is turned on,
also of the daughter particles.
The variables of daughters before the vertex fit can be accessed with the meta-variable originalDaughter
.
For the variables of the mother particle, one can store the quantities in the extraInfo field by running
variablesToExtraInfo
before the vertex fit and then accessing them via the variable extraInfo
.
- vertex.TagV(list_name, MCassociation='', confidenceLevel=0.0, trackFindingType='standard_PXD', constraintType='tube', askMCInfo=False, reqPXDHits=0, maskName='all', fitAlgorithm='KFit', kFitReqReducedChi2=5.0, useTruthInFit=False, useRollBack=False, path=None)[source]#
For each Particle in the given Breco ParticleList: perform the fit of tag side using the track list from the RestOfEvent dataobject save the MC Btag in case of signal MC
- Parameters
list_name (str) – name of the input Breco ParticleList
MCassociation (str) – use standard MC association or the internal one
confidenceLevel (float) – minimum value of the ConfidenceLevel to accept the fit. 0 selects CL > 0
constraintType (str) –
choose the constraint used in the fit. Can be set to
noConstraint;
IP: default, tag B constrained to be on the IP;
tube: tube along the tag B line of flight, only for fully reconstructed signal B;
boost: long tube along the boost direction;
(breco): deprecated, but similar to tube;
trackFindingType (str) –
choose how to look for tag tracks. Can be set to
standard: all tracks except from Kshorts;
- standard_PXD: default, same as above but consider only tracks with at least 1 PXD hit.
If the fit fails, attempt again with the standard option;
fitAlgorithm (str) – Fitter used for the tag vertex fit: Rave or KFit (default)
kFitReqReducedChi2 (float) – The required chi2/ndf to accept the kFit result, if it is higher, iteration procedure is applied
askMCInfo (bool) – True when requesting MC Information from the tracks performing the vertex fit
reqPXDHits (int) – minimum N PXD hits for a track (default is 0)
maskName (str) – get particles from a specified ROE mask
useTruthInFit (bool) – True when the tag vertex fit is performed with the true momentum and position of the tracks (default is false). The variable
TagVFitTruthStatus
is set to 1 if the truth-matching succeeds and 2 otherwise.useRollBack (bool) – True when the tag vertex fit is performed with position of tracks rolled back to position of the mother B (default is false). The variable
TagVRollBackStatus
is set to 1 if the truth-matching succeeds and 2 otherwise.path (basf2.Path) – modules are added to this path
Warning
Note that the useFitAlgorithm (str) parameter is deprecated and replaced by constraintType (str) and trackFindingType (str)
Warning
The trackFindingType
singleTrack
andsingleTrack_PXD
are broken and cannot be used any more.
- vertex.fitPseudo(list_name, path)[source]#
Add a pseudo “vertex fit” which adds a covariance matrix from the combination of the four-vectors of the daughters. This is similar to BaBar’s “Add4” function. It is commonly used for \(\pi^0\to\gamma\gamma\) reconstruction where a vertex fit is not possible.
Here is the basic usage:
from modularAnalysis import fitPseudo from stdPi0s import stdPi0s stdPi0s("eff40_May2020", path=mypath) fitPseudo("pi0:eff40_May2020", path=mypath)
- Parameters
list_name (str) – the name of the list to add the covariance matrix to
path (basf2.Path) – modules are added to this path
- vertex.fitVertex(list_name, conf_level, decay_string='', fitter='KFit', fit_type='vertex', constraint='', massConstraint=[], recoilMass=0, daughtersUpdate=False, smearing=0, path=None)[source]#
Perform the specified fit for each Particle in the given ParticleList.
- Info:
Direct use of
fitVertex
is not recommended unless you know what you are doing. If you’re unsure, you probably want to usetreeFit
orkFit
.
- Parameters
list_name (str) – name of the input ParticleList
conf_level (float) – minimum value of the confidence level to accept the fit. Setting this parameter to -1 selects all particle candidates. The value of 0 rejects the particle candidates with failed fit.
decay_string (str) – select particles used for the vertex fit
fitter (str) – Rave or KFit
fit_type (str) – type of the kinematic fit (valid options are vertex/massvertex/mass/fourC/massfourC/recoilmass)
constraint (str) – add additional constraint to the fit (valid options are empty string/ipprofile/iptube/mother)
massConstraint (list(int) or list(str)) – list of PDG ids or Names of the particles which are mass-constrained Please do not mix PDG id and particle names in massConstraint list (valid only for massfourC).
recoilMass (float) – invariant mass of recoil in GeV (valid only for recoilmass)
daughtersUpdate (bool) – make copy of the daughters and update them after the vertex fit
smearing (float) – IP tube width is smeared by this value (cm). meaningful only with ‘KFit/vertex/iptube’ option.
path (basf2.Path) – modules are added to this path
- vertex.kFit(list_name, conf_level, fit_type='vertex', constraint='', daughtersUpdate=False, decay_string='', massConstraint=[], recoilMass=0, smearing=0, path=None)[source]#
Perform KFit for each Particle in the given ParticleList.
- Parameters
list_name (str) – name of the input ParticleList
conf_level (float) – minimum value of the confidence level to accept the fit Setting this parameter to -1 selects all particle candidates. The value of 0 rejects particle candidates with a failed fit.
fit_type (str) –
type of the kinematic fit. Valid options are
mass
for a mass-constrained fitvertex
for a vertex fitmassvertex
for a vertex fit with a mass constraint on the mother particlefourC
for a vertex fit in which the mother particle’s four-momentum is constrained to the beam four-momentummassfourC
for a vertex fit with a 4-momentum constraint and mass constraints on the specified daughter particlesrecoilmass
for kinematic fit in which the mass of the mother particle’s recoil four-momentum with respect to the beam four-momentum is constrained
constraint (str) – add an additional constraint to the fit (valid options are ipprofile or iptube)
massConstraint (list(int) or list(str)) – list of PDG ids or Names of the particles which are mass-constrained Please do not mix PDG id and particle names in massConstraint list (valid only for massfourC).
recoilMass (float) – invariant mass of recoil in GeV (valid only for recoilmass)
daughtersUpdate (bool) – make copy of the daughters and update them after the KFit
decay_string (str) – select particles used for the KFit
smearing (float) – IP tube width is smeared by this value (cm). meaningful only with ‘iptube’ constraint.
path (basf2.Path) – modules are added to this path
- vertex.raveFit(list_name, conf_level, fit_type='vertex', decay_string='', constraint='', daughtersUpdate=False, path=None, silence_warning=False)[source]#
Performs a vertex fit using RAVE for each Particle in the given ParticleList.
Warning
RAVE is deprecated since it is not maintained. Whilst we will not remove RAVE, it is not recommended for analysis use, other than benchmarking or legacy studies. Instead, we recommend Tree Fitter (
vertex.treeFit
) orvertex.kFit
.- Parameters
list_name (str) – name of the input ParticleList
conf_level (float) – minimum value of the confidence level to accept the fit. Setting this parameter to -1 selects all particle candidates. The value of 0 rejects the particle candidates with failed fit.
fit_type (str) –
type of the RAVE vertex fit.Valid options are
mass
for a mass-constrained fit (the 7x7 error matrix of the mother particle has to be defined)vertex
for a vertex fit without any mass constraintmassvertex
for a mass-constrained vertex fit
decay_string (str) – select particles used for the vertex fit
constraint (str) – add additional constraint to the fit (valid options are ipprofile or iptube).
daughtersUpdate (bool) – make copy of the daughters and update them after the Rave vertex fit
path (basf2.Path) – modules are added to this path
silence_warning (bool) – silence the warning advertising TreeFitter use
- vertex.treeFit(list_name, conf_level=0.001, massConstraint=[], ipConstraint=False, updateAllDaughters=False, customOriginConstraint=False, customOriginVertex=[0.001, 0, 0.0116], customOriginCovariance=[0.0048, 0, 0, 0, 0.003567, 0, 0, 0, 0.04], originDimension=3, treatAsInvisible='', ignoreFromVertexFit='', path=None)[source]#
Perform a Tree Fitter fit for each Particle in the given ParticleList.
- Example
An example of usage for the decay chain \(B^0\to\pi^+\pi^-\pi^0\) is the following:
reconstructDecay('pi0:A -> gamma:pi0 gamma:pi0', '0.130 < InvM < 0.14', path=mypath) reconstructDecay('B0:treefit -> pi+:my pi-:my pi0:A ', '', path=mypath) treeFit('B0:treefit', ipConstraint=True, path=mypath)
Note
The Particle object loaded from the KLMCluster does not have proper covariance matrix yet (by release-06 at least). The performance of TreeFit with these particles is not guaranteed. Alternatively, one can perform the TreeFit ignoring these particles from the vertex fit with the option
ignoreFromVertexFit
.- Parameters
list_name (str) – name of the input ParticleList
conf_level (float) – minimum value of the confidence level to accept the fit. Setting this parameter to -1 selects all particle candidates. The value of 0 rejects the particle candidates with failed fit.
massConstraint (list(int) or list(str)) – list of PDG ids or Names of the particles which are mass-constrained Please do not mix PDG id and particle names in massConstraint list.
ipConstraint (bool) – constrain head production vertex to IP (x-y-z) constraint
customOriginConstraint (bool) – use a custom origin vertex as the production vertex of your particle. This is useful when fitting D*/D without wanting to fit a B but constraining the process to be B-decay-like. (think of semileptonic modes and stuff with a neutrino in the B decay).
customOriginVertex (list(float)) – 3d vector of the vertex coordinates you want to use as custom origin. Default numbers are taken for B-mesons
customOriginCovariance (list(float)) – 3x3 covariance matrix for the custom vertex (type: vector). Default numbers extracted from generator distribution width of B-mesons.
updateAllDaughters (bool) – if true the entire tree will be updated with the fitted values for momenta and vertex position. Otherwise only the momenta of the head of the tree will be updated, however for all daughters we also update the vertex position with the fit results as this would otherwise be set to {0, 0, 0} contact us if this causes any hardship/confusion.
originDimension (int) – If the origin or IP constraint (
customOriginVertex
oripConstraint
) are used, this specifies the dimension of the constraint (3D or 2D).treatAsInvisible (str) – Decay string to select one particle that will be treated as invisible in the fit.
ignoreFromVertexFit (str) – Decay string to select particles that will be ignored to determine the vertex position.
path (basf2.Path) – modules are added to this path