Class: PDG::Particle

Inherits:
Object
  • Object
show all
Defined in:
lib/pdg/particle.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(properties) ⇒ Particle

Returns a new instance of Particle.



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# File 'lib/pdg/particle.rb', line 11

def initialize(properties)
  properties.update(properties) { |key, val| val.nil? ? 0 : val }
  @id       = properties[:id].to_i
  @name     = properties[:name]
  @charge   = case properties[:charge]
              when "+"
                1.0
              when "++"
                2.0
              when "-"
                -1.0
              when "--"
                -2.0
              # Either 0 or something like -1/3, +2/3
              else
                fraction_to_float properties[:charge]
              end
  # The mass and width keys may not be present, but never fear as:
  # nil.to_f => 0.0
  @mass     = properties[:mass].to_f
  @width    = properties[:width].to_f
  @tex      = name_to_tex
end

Instance Attribute Details

#charge ⇒ Object (readonly) Also known as: q

Returns the value of attribute charge.



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# File 'lib/pdg/particle.rb', line 5

def charge
  @charge
end

#id ⇒ Object (readonly)

Returns the value of attribute id.



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# File 'lib/pdg/particle.rb', line 5

def id
  @id
end

#mass ⇒ Object Also known as: m

Returns the value of attribute mass.



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# File 'lib/pdg/particle.rb', line 5

def mass
  @mass
end

#name ⇒ Object (readonly)

Returns the value of attribute name.



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# File 'lib/pdg/particle.rb', line 5

def name
  @name
end

#tex ⇒ Object (readonly)

Returns the value of attribute tex.



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# File 'lib/pdg/particle.rb', line 5

def tex
  @tex
end

#width ⇒ Object

Returns the value of attribute width.



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# File 'lib/pdg/particle.rb', line 6

def width
  @width
end

Instance Method Details

#ctau ⇒ Object

Returns c tau distance in mm (10^-3 m)



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# File 'lib/pdg/particle.rb', line 45

def ctau
  @ctau ||= @lifetime == 0.0 ? 0.0 : SPEED_OF_LIGHT * lifetime
end

#lifetime ⇒ Object Also known as: tau

Returns the lifetime in picoseconds (10^-12 s) by Gamma = hbar / tau. Returns 0 for zero lifetimes. (The PDG represent inifinite lifetimes, like that of the proton, as zero.)



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# File 'lib/pdg/particle.rb', line 39

def lifetime
  @lifetime ||= @width == 0.0 ? 0.0 : HBAR / @width
end

#mean_distance(energy) ⇒ Object

Returns the mean displacement, in mm, of the particle with energy ‘energy` in GeV



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# File 'lib/pdg/particle.rb', line 50

def mean_distance(energy)
  return 0.0 if lifetime == 0.0
  if energy < @mass
    raise LorentzViolation,
      "Energy #{energy} GeV is less than particle mass #{@mass} GeV for particle #{self}"
  end

  gamma = energy.to_f / @mass
  beta  = Math.sqrt(1.0 - (gamma**-2))
  ctau * beta * gamma
end

#to_s ⇒ Object

TODO pretty printing



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# File 'lib/pdg/particle.rb', line 63

def to_s
  "#{@name}: ID=#{@id}, m=#{@mass} GeV, q=#{@charge}, width=#{@width} GeV"
end