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Package hepmc

v0.27.0
Latest Go to latest

The highest tagged major version is .

Published: May 20, 2020 | License: BSD-3-Clause | Module: go-hep.org/x/hep

Overview

Package hepmc is a pure Go implementation of the C++ HepMC-2 library.

Index

Examples

func Delete

func Delete(evt *Event) error

Delete deletes an event and allows memory to be reclaimed by the garbage collector

func VersionName

func VersionName() string

VersionName returns the hepmc version string.

type CrossSection

type CrossSection struct {
	Value float64 // value of the cross-section (in pb)
	Error float64 // error on the value of the cross-section (in pb)

}

CrossSection is used to store the generated cross section. This type is meant to be used to pass, on an event by event basis, the current best guess of the total cross section. It is expected that the final cross section will be stored elsewhere.

type Decoder

type Decoder struct {
	// contains filtered or unexported fields
}

Decoder decodes a hepmc Event from a stream

func NewDecoder

func NewDecoder(r io.Reader) *Decoder

NewDecoder returns a new hepmc Decoder that reads from the io.Reader.

func (*Decoder) Decode

func (dec *Decoder) Decode(evt *Event) error

Decode reads the next value from the stream and stores it into evt.

type Encoder

type Encoder struct {
	// contains filtered or unexported fields
}

Encoder encodes a hepmc Event into a stream.

func NewEncoder

func NewEncoder(w io.Writer) *Encoder

NewEncoder returns a new hepmc Encoder that writes into the io.Writer.

func (*Encoder) Close

func (enc *Encoder) Close() error

Close closes the encoder and adds a footer to the stream.

func (*Encoder) Encode

func (enc *Encoder) Encode(evt *Event) error

Encode writes evt into the stream.

type Event

type Event struct {
	SignalProcessID int     // id of the signal process
	EventNumber     int     // event number
	Mpi             int     // number of multi particle interactions
	Scale           float64 // energy scale,
	AlphaQCD        float64 // QCD coupling, see hep-ph/0109068
	AlphaQED        float64 // QED coupling, see hep-ph/0109068

	SignalVertex *Vertex      // signal vertex
	Beams        [2]*Particle // incoming beams
	Weights      Weights      // weights for this event. first weight is used by default for hit and miss
	RandomStates []int64      // container of random number generator states

	Vertices  map[int]*Vertex
	Particles map[int]*Particle

	CrossSection *CrossSection
	HeavyIon     *HeavyIon
	PdfInfo      *PdfInfo
	MomentumUnit MomentumUnit
	LengthUnit   LengthUnit
	// contains filtered or unexported fields
}

Event represents a record for MC generators (for use at any stage of generation)

This type is intended as both a "container class" ( to store a MC

event for interface between MC generators and detector simulation )
and also as a "work in progress class" ( that could be used inside
a generator and modified as the event is built ).
Example (BuildFromScratch)

This example will place the following event into HepMC "by hand"

   name status pdg_id  parent Px       Py    Pz       Energy      Mass
1  !p+!    3   2212    0,0    0.000    0.000 7000.000 7000.000    0.938
2  !p+!    3   2212    0,0    0.000    0.000-7000.000 7000.000    0.938

=========================================================================

3  !d!     3      1    1,1    0.750   -1.569   32.191   32.238    0.000
4  !u~!    3     -2    2,2   -3.047  -19.000  -54.629   57.920    0.000
5  !W-!    3    -24    1,2    1.517   -20.68  -20.605   85.925   80.799
6  !gamma! 1     22    1,2   -3.813    0.113   -1.833    4.233    0.000
7  !d!     1      1    5,5   -2.445   28.816    6.082   29.552    0.010
8  !u~!    1     -2    5,5    3.962  -49.498  -26.687   56.373    0.006

now we build the graph, which will look like

#                       p7                         #
# p1                   /                           #
#   \v1__p3      p5---v4                           #
#         \_v3_/       \                           #
#         /    \        p8                         #
#    v2__p4     \                                  #
#   /            p6                                #
# p2                                               #
#                                                  #

Code:

package main

import (
	"bytes"
	"fmt"
	"go-hep.org/x/hep/fmom"
	"go-hep.org/x/hep/hepmc"
	"log"
	"os"
)

func main() {
	var err error

	// first create the event container, with signal process 20, event number 1
	evt := hepmc.Event{
		SignalProcessID: 20,
		EventNumber:     1,
		Particles:       make(map[int]*hepmc.Particle),
		Vertices:        make(map[int]*hepmc.Vertex),
	}
	defer evt.Delete()

	// define the units
	evt.MomentumUnit = hepmc.GEV
	evt.LengthUnit = hepmc.MM

	// create vertex 1 and 2, together with their in-particles
	v1 := &hepmc.Vertex{}
	err = evt.AddVertex(v1)
	if err != nil {
		log.Fatal(err)
	}

	err = v1.AddParticleIn(&hepmc.Particle{
		Momentum: fmom.NewPxPyPzE(0, 0, 7000, 7000),
		PdgID:    2212,
		Status:   3,
	})
	if err != nil {
		log.Fatal(err)
	}

	v2 := &hepmc.Vertex{}
	err = evt.AddVertex(v2)
	if err != nil {
		log.Fatal(err)
	}

	err = v2.AddParticleIn(&hepmc.Particle{
		Momentum: fmom.NewPxPyPzE(0, 0, -7000, 7000),
		PdgID:    2212,
		Status:   3,
		//Barcode:  2,
	})
	if err != nil {
		log.Fatal(err)
	}

	// create the outgoing particles of v1 and v2
	p3 := &hepmc.Particle{
		Momentum: fmom.NewPxPyPzE(.750, -1.569, 32.191, 32.238),
		PdgID:    1,
		Status:   3,
		// Barcode: 3,
	}
	err = v1.AddParticleOut(p3)
	if err != nil {
		log.Fatal(err)
	}

	p4 := &hepmc.Particle{
		Momentum: fmom.NewPxPyPzE(-3.047, -19., -54.629, 57.920),
		PdgID:    -2,
		Status:   3,
		// Barcode: 4,
	}
	err = v2.AddParticleOut(p4)
	if err != nil {
		log.Fatal(err)
	}

	// create v3
	v3 := &hepmc.Vertex{}
	err = evt.AddVertex(v3)
	if err != nil {
		log.Fatal(err)
	}

	err = v3.AddParticleIn(p3)
	if err != nil {
		log.Fatal(err)
	}

	err = v3.AddParticleIn(p4)
	if err != nil {
		log.Fatal(err)
	}

	err = v3.AddParticleOut(&hepmc.Particle{
		Momentum: fmom.NewPxPyPzE(-3.813, 0.113, -1.833, 4.233),
		PdgID:    22,
		Status:   1,
	})
	if err != nil {
		log.Fatal(err)
	}

	p5 := &hepmc.Particle{
		Momentum: fmom.NewPxPyPzE(1.517, -20.68, -20.605, 85.925),
		PdgID:    -24,
		Status:   3,
	}
	err = v3.AddParticleOut(p5)
	if err != nil {
		log.Fatal(err)
	}

	// create v4
	v4 := &hepmc.Vertex{
		Position: fmom.NewPxPyPzE(0.12, -0.3, 0.05, 0.004),
	}
	err = evt.AddVertex(v4)
	if err != nil {
		log.Fatal(err)
	}

	err = v4.AddParticleIn(p5)
	if err != nil {
		log.Fatal(err)
	}

	err = v4.AddParticleOut(&hepmc.Particle{
		Momentum: fmom.NewPxPyPzE(-2.445, 28.816, 6.082, 29.552),
		PdgID:    1,
		Status:   1,
	})
	if err != nil {
		log.Fatal(err)
	}

	err = v4.AddParticleOut(&hepmc.Particle{
		Momentum: fmom.NewPxPyPzE(3.962, -49.498, -26.687, 56.373),
		PdgID:    -2,
		Status:   1,
	})
	if err != nil {
		log.Fatal(err)
	}

	evt.SignalVertex = v3

	err = evt.Print(os.Stdout)
	if err != nil {
		log.Fatal(err)
	}

	out := new(bytes.Buffer)
	enc := hepmc.NewEncoder(out)
	err = enc.Encode(&evt)
	if err != nil {
		log.Fatal(err)
	}

	fmt.Printf("%s\n", out.Bytes())

}
________________________________________________________________________________
GenEvent: #0001 ID=   20 SignalProcessGenVertex Barcode: -3
 Momentum units:     GEV     Position units:      MM
 Entries this event: 4 vertices, 8 particles.
 Beam Particles are not defined.
 RndmState(0)=
 Wgts(0)=
 EventScale 0.00000 [energy] 	 alphaQCD=0.00000000	 alphaQED=0.00000000
                                    GenParticle Legend
        Barcode   PDG ID      ( Px,       Py,       Pz,     E ) Stat  DecayVtx
________________________________________________________________________________
GenVertex:       -1 ID:    0 (X,cT):0
 I: 1         1     2212 +0.00e+00,+0.00e+00,+7.00e+03,+7.00e+03   3        -1
 O: 1         3        1 +7.50e-01,-1.57e+00,+3.22e+01,+3.22e+01   3        -3
GenVertex:       -2 ID:    0 (X,cT):0
 I: 1         2     2212 +0.00e+00,+0.00e+00,-7.00e+03,+7.00e+03   3        -2
 O: 1         4       -2 -3.05e+00,-1.90e+01,-5.46e+01,+5.79e+01   3        -3
GenVertex:       -3 ID:    0 (X,cT):0
 I: 2         3        1 +7.50e-01,-1.57e+00,+3.22e+01,+3.22e+01   3        -3
              4       -2 -3.05e+00,-1.90e+01,-5.46e+01,+5.79e+01   3        -3
 O: 2         5       22 -3.81e+00,+1.13e-01,-1.83e+00,+4.23e+00   1
              6      -24 +1.52e+00,-2.07e+01,-2.06e+01,+8.59e+01   3        -4
Vertex:       -4 ID:    0 (X,cT)=+1.20e-01,-3.00e-01,+5.00e-02,+4.00e-03
 I: 1         6      -24 +1.52e+00,-2.07e+01,-2.06e+01,+8.59e+01   3        -4
 O: 2         7        1 -2.44e+00,+2.88e+01,+6.08e+00,+2.96e+01   1
              8       -2 +3.96e+00,-4.95e+01,-2.67e+01,+5.64e+01   1
________________________________________________________________________________

HepMC::Version 2.06.09
HepMC::IO_GenEvent-START_EVENT_LISTING
E 1 0 0.0000000000000000e+00 0.0000000000000000e+00 0.0000000000000000e+00 20 -3 4 0 0 0 0
U GEV MM
F 0 0 0.0000000000000000e+00 0.0000000000000000e+00 0.0000000000000000e+00 0.0000000000000000e+00 0.0000000000000000e+00 0 0
V -1 0 0.0000000000000000e+00 0.0000000000000000e+00 0.0000000000000000e+00 0.0000000000000000e+00 1 1 0
P 1 2212 0.0000000000000000e+00 0.0000000000000000e+00 7.0000000000000000e+03 7.0000000000000000e+03 0.0000000000000000e+00 3 0.0000000000000000e+00 0.0000000000000000e+00 -1 0
P 3 1 7.5000000000000000e-01 -1.5690000000000000e+00 3.2191000000000003e+01 3.2238000000000000e+01 0.0000000000000000e+00 3 0.0000000000000000e+00 0.0000000000000000e+00 -3 0
V -2 0 0.0000000000000000e+00 0.0000000000000000e+00 0.0000000000000000e+00 0.0000000000000000e+00 1 1 0
P 2 2212 0.0000000000000000e+00 0.0000000000000000e+00 -7.0000000000000000e+03 7.0000000000000000e+03 0.0000000000000000e+00 3 0.0000000000000000e+00 0.0000000000000000e+00 -2 0
P 4 -2 -3.0470000000000002e+00 -1.9000000000000000e+01 -5.4628999999999998e+01 5.7920000000000002e+01 0.0000000000000000e+00 3 0.0000000000000000e+00 0.0000000000000000e+00 -3 0
V -3 0 0.0000000000000000e+00 0.0000000000000000e+00 0.0000000000000000e+00 0.0000000000000000e+00 0 2 0
P 5 22 -3.8130000000000002e+00 1.1300000000000000e-01 -1.8330000000000000e+00 4.2329999999999997e+00 0.0000000000000000e+00 1 0.0000000000000000e+00 0.0000000000000000e+00 0 0
P 6 -24 1.5169999999999999e+00 -2.0680000000000000e+01 -2.0605000000000000e+01 8.5924999999999997e+01 0.0000000000000000e+00 3 0.0000000000000000e+00 0.0000000000000000e+00 -4 0
V -4 0 1.2000000000000000e-01 -2.9999999999999999e-01 5.0000000000000003e-02 4.0000000000000001e-03 0 2 0
P 7 1 -2.4449999999999998e+00 2.8815999999999999e+01 6.0819999999999999e+00 2.9552000000000000e+01 0.0000000000000000e+00 1 0.0000000000000000e+00 0.0000000000000000e+00 0 0
P 8 -2 3.9620000000000002e+00 -4.9497999999999998e+01 -2.6687000000000001e+01 5.6372999999999998e+01 0.0000000000000000e+00 1 0.0000000000000000e+00 0.0000000000000000e+00 0 0

func (*Event) AddVertex

func (evt *Event) AddVertex(vtx *Vertex) error

AddVertex adds a vertex to this event

func (*Event) Delete

func (evt *Event) Delete() error

Delete prepares this event for GC-reclaim

func (*Event) Print

func (evt *Event) Print(w io.Writer) error

Print prints the event to w in a human-readable format

type Flow

type Flow struct {
	Particle *Particle   // the particle this flow describes
	Icode    map[int]int // flow patterns as (code_index, icode)
}

Flow represents a particle's flow and keeps track of an arbitrary number of flow patterns within a graph (i.e. color flow, charge flow, lepton number flow,...)

Flow patterns are coded with an integer, in the same manner as in Herwig. Note: 0 is NOT allowed as code index nor as flow code since it

is used to indicate null.

This class can be used to keep track of flow patterns within

a graph. An example is color flow. If we have two quarks going through
an s-channel gluon to form two more quarks:

\q1       /q3   then we can keep track of the color flow with the
 \_______/      HepMC::Flow class as follows:
 /   g   \.
/q2       \q4

lets say the color flows from q2-->g-->q3  and q1-->g-->q4
the individual colors are unimportant, but the flow pattern is.
We can capture this flow by assigning the first pattern (q2-->g-->q3)
a unique (arbitrary) flow code 678 and the second pattern (q1-->g-->q4)
flow code 269  ( you can ask HepMC::Flow to choose
a unique code for you using Flow::set_unique_icode() ).
these codes with the particles as follows:
  q2->flow().set_icode(1,678);
  g->flow().set_icode(1,678);
  q3->flow().set_icode(1,678);
  q1->flow().set_icode(1,269);
  g->flow().set_icode(2,269);
  q4->flow().set_icode(1,269);
later on if we wish to know the color partner of q1 we can ask for a list
of all particles connected via this code to q1 which do have less than
2 color partners using:
  vector<GenParticle*> result=q1->dangling_connected_partners(q1->icode(1),1,2);
this will return a list containing q1 and q4.
  vector<GenParticle*> result=q1->connected_partners(q1->icode(1),1,2);
would return a list containing q1, g, and q4.

type HeavyIon

type HeavyIon struct {
	NCollHard         int     // number of hard scatterings
	NPartProj         int     // number of projectile participants
	NPartTarg         int     // number of target participants
	NColl             int     // number of NN (nucleon-nucleon) collisions
	NNwColl           int     // Number of N-Nwounded collisions
	NwNColl           int     // Number of Nwounded-N collisons
	NwNwColl          int     // Number of Nwounded-Nwounded collisions
	SpectatorNeutrons int     // Number of spectators neutrons
	SpectatorProtons  int     // Number of spectators protons
	ImpactParameter   float32 // Impact Parameter(fm) of collision
	EventPlaneAngle   float32 // Azimuthal angle of event plane
	Eccentricity      float32 // eccentricity of participating nucleons in the transverse plane (as in phobos nucl-ex/0510031)
	SigmaInelNN       float32 // nucleon-nucleon inelastic (including diffractive) cross-section
}

HeavyIon holds additional information for heavy-ion collisions

type LengthUnit

type LengthUnit int

LengthUnit describes the units of length quantities (mm or cm)

const (
	// MM is a Length in mm (default)
	MM LengthUnit = iota
	// CM is a Length in cm
	CM
)

func LengthUnitFromString

func LengthUnitFromString(s string) (LengthUnit, error)

LengthUnitFromString creates a LengthUnit value from its string representation

func (LengthUnit) String

func (lu LengthUnit) String() string

type MomentumUnit

type MomentumUnit int

MomentumUnit describes the units of momentum quantities (MeV or GeV)

const (
	// MEV is a Momentum in MeV (default)
	MEV MomentumUnit = iota
	// GEV is a Momentum in GeV
	GEV
)

func MomentumUnitFromString

func MomentumUnitFromString(s string) (MomentumUnit, error)

MomentumUnitFromString creates a MomentumUnit value from its string representation

func (MomentumUnit) String

func (mu MomentumUnit) String() string

type Particle

type Particle struct {
	Momentum      fmom.PxPyPzE // momentum vector
	PdgID         int64        // id according to PDG convention
	Status        int          // status code as defined for HEPEVT
	Flow          Flow         // flow of this particle
	Polarization  Polarization // polarization of this particle
	ProdVertex    *Vertex      // pointer to production vertex (nil if vacuum or beam)
	EndVertex     *Vertex      // pointer to decay vertex (nil if not-decayed)
	Barcode       int          // unique identifier in the event
	GeneratedMass float64      // mass of this particle when it was generated
}

Particle represents a generator particle within an event coming in/out of a vertex

Particle is the basic building block of the event record

type Particles

type Particles []*Particle

Particles is a []*Particle sorted by increasing-barcodes

func (Particles) Len

func (ps Particles) Len() int

func (Particles) Less

func (ps Particles) Less(i, j int) bool

func (Particles) Swap

func (ps Particles) Swap(i, j int)

type PdfInfo

type PdfInfo struct {
	ID1      int     // flavour code of first parton
	ID2      int     // flavour code of second parton
	LHAPdf1  int     // LHA PDF id of first parton
	LHAPdf2  int     // LHA PDF id of second parton
	X1       float64 // fraction of beam momentum carried by first parton ("beam side")
	X2       float64 // fraction of beam momentum carried by second parton ("target side")
	ScalePDF float64 // Q-scale used in evaluation of PDF's   (in GeV)
	Pdf1     float64 // PDF (id1, x1, Q)
	Pdf2     float64 // PDF (id2, x2, Q)
}

PdfInfo holds informations about the partons distribution functions

type Polarization

type Polarization struct {
	Theta float64 // polar angle of polarization in radians [0, math.Pi)
	Phi   float64 // azimuthal angle of polarization in radians [0, 2*math.Pi)
}

Polarization holds informations about a particle's polarization

type Vertex

type Vertex struct {
	Position     fmom.PxPyPzE // 4-vector of vertex [mm]
	ParticlesIn  []*Particle  // all incoming particles
	ParticlesOut []*Particle  // all outgoing particles
	ID           int          // vertex id
	Weights      Weights      // weights for this vertex
	Event        *Event       // pointer to event owning this vertex
	Barcode      int          // unique identifier in the event
}

Vertex represents a generator vertex within an event A vertex is indirectly (via particle "edges") linked to other

vertices ("nodes") to form a composite "graph"

func (*Vertex) AddParticleIn

func (vtx *Vertex) AddParticleIn(p *Particle) error

AddParticleIn adds a particle to the list of in-coming particles to this vertex

func (*Vertex) AddParticleOut

func (vtx *Vertex) AddParticleOut(p *Particle) error

AddParticleOut adds a particle to the list of out-going particles to this vertex

func (*Vertex) Print

func (vtx *Vertex) Print(w io.Writer) error

Print prints the vertex to w in a human-readable format

type Vertices

type Vertices []*Vertex

Vertices is a []*Vertex sorted by increasing-barcodes

func (Vertices) Len

func (ps Vertices) Len() int

func (Vertices) Less

func (ps Vertices) Less(i, j int) bool

func (Vertices) Swap

func (ps Vertices) Swap(i, j int)

type Weights

type Weights struct {
	Slice []float64      // the slice of weight values
	Map   map[string]int // the map of name->index-in-the-slice
}

Weights holds informations about the event's and vertices' generation weights.

func NewWeights

func NewWeights() Weights

NewWeights creates a new set of weights.

func (Weights) Add

func (w Weights) Add(n string, v float64) error

Add adds a new weight with name n and value v.

func (Weights) At

func (w Weights) At(n string) float64

At returns the weight's value named n.

Package Files

Documentation was rendered with GOOS=linux and GOARCH=amd64.

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