# Introduction

This lists the filters recommended for use in the HLT and the selections. See DaVinciTutorial4 for a hands-on tutorial. A longer, but not necessarily up-to-date, list can be found at LoKiParticleFunctions. It also contains examples on how to use these functors in C++ code.

# Particle Functors

## ALL: All

Takes all particles. This is required if one wants to apply no cut.
CombineParticles.FILTER0.Code = "(ALL)" ;

## ABSID: Absolute value of PID.

Returns the absolute value of the PID. The following lines are equivalent:
CombineParticles.FILTER0.Code = "(ABSID==211) " ;
CombineParticles.FILTER0.Code = "(ABSID=='pi+') " ;
CombineParticles.FILTER0.Code = "(ABSID=='pi-') " ;
Note the last line! The comparison (ABSID=='pi-') takes the absolute value on both sides. This avoid having to remember that the has a positive pid (211) while the has a negative pid (-13).

The pid can also be used without the absolute value. See ID.

## ADMASS: The absolute mass difference to the reference value

Calculates the absolute difference between the measured mass and the PDG reference value. It takes the pid of the reference particle as argument.
HltSharedKsLL.FILTER1.Code = "(ADMASS('KS0')<50)"

The mass difference can also be used without the absolute value. See DMASS.

TODO : A version without argument will be provided where the ID of the particle is used to get the reference mass.

## BPVDIRA: Direction angle

Computes the cosine of the angle between the momentum of the particle and the direction fo flight from the best PV to the decay vertex.
CombineParticles.FILTER2.Code = "(BPVDIRA>0.9999)" ;

## BPVIPCHI2(): IP on related PV

Computes the -IP on the related PV.
CombineParticles.FILTER2.Code = "BPVIPCHI2()<25" ;
So far it needs the ().

## BPVVDCHI2: -separation from related PV

Computes the -distance from the related PV.
CombineParticles.FILTER2.Code = "(BPVVDCHI2>100)" ;

## DMASS: The mass difference to the reference value

Calculates the difference between the measured mass and the PDG reference value. It takes the pid of the reference particle as argument. In most reasonable cases one will use the absolute mass difference (see DMASS) or the mass itself (see MM).

## ID:

CombineParticles.FILTER2.Code = "" ;

## INTREE: In tree

Requires there is a particle in the decay tree satisfying the requirements.
FilterDesktop.Filter.Code = "(INTREE( (ID=='J/psi(1S)') & (BPVVDCHI2>25) ) )" ;
Requires there is a in the tree more than 5\sigma away from the best vertex.

## MAXTREE:

CombineParticles.FILTER2.Code = "" ;

## MINTREE: Minimal value in the decay tree

Takes a functor as agrument and returns its minimal value searching through the decay tree.
CombineParticles.FILTER0.Code = "(MINTREE(ABSID=='K+',PT)>1400)" ;
This would look for all particles kaons in the decay tree and find their and return the minimum. The cut then requires that all kaon descendents ahve a .

## MIPCHI2DV:

CombineParticles.FILTER2.Code = "" ;

## MIPDV:

CombineParticles.FILTER2.Code = "" ;

## M:

CombineParticles.FILTER2.Code = "" ;

## MM:

CombineParticles.FILTER2.Code = "" ;

## NINTREE: Number of particles in tree

Returns the number of particles in a tree satisfying some selection criteria.
CombineParticles.FILTER0.Code = "( 2 == NINTREE( (ABSID=='e-') & (PT>1000)))" ;
Requires that there are two electrons in the tree with .

## P:

CombineParticles.FILTER2.Code = "" ;

## PIDe, ==, :

CombineParticles.FILTER2.Code = "" ;

## PT:

CombineParticles.FILTER2.Code = "" ;

## TRCHI2DOF:

CombineParticles.FILTER2.Code = "" ;

## VDMIN:

CombineParticles.FILTER2.Code = "" ;

## VFASPF: Vertex Function as Particle Function.

Allows to apply vertex functors to the particle's endVertex().
CombineParticles.FILTER2.Code = "(VFASPF(VCHI2/VDOF)<10)" ;
Applies a cut to the vertex of the particle.

# Vertex functors

Vertex functors are accessed using VFASPF.

## VCHI2

CombineParticles.FILTER2.Code = "" ;

## VDOF

CombineParticles.FILTER2.Code = "" ;

--+ Syntax

-- PatrickKoppenburg - 27 Mar 2008

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Topic revision: r2 - 2008-03-28 - unknown

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