Model definition:

model = SM

Neutrino and quark containers:

alias n = n1:n2:n3
alias N = N1:N2:N3
alias q = u:d:s:c
alias Q = U:D:S:C

The Higgsstrahlung process

process zh = e1, E1 => Z, h

The missing-energy channel

process nnbb = e1, E1 => n, N, b, B

Other channels (for the 4-jet channels we combine EW and QCD contributions)

process qqbb = e1, E1 => q, Q, b, B
process bbbb = e1, E1 => b, B, b, B
process eebb = e1, E1 => e1, E1, b, B
process qqtt = e1, E1 => q, Q, e3, E3
process bbtt = e1, E1 => b, B, e3, E3

Compilation (optional)

compile

The final LEP energy:

sqrts = 209 GeV

Set the input parameters

mH = 115 GeV
wH = 3.228 MeV
# Running b mass
mb = 2.9 GeV
me = 0
ms = 0
mc = 0

Soft-collinear cuts for the jets

cuts = all M >= 10 GeV [q,Q]

Integrate the processes:

integrate (zh) { iterations = 5:5000}

integrate(nnbb,qqbb,bbbb,eebb,
          qqtt,bbtt) { iterations = 12:20000 }

Define title etc. as global variables, that will be used by PLOT

$description =
  "A WHIZARD 2.0 Example. Using weighted events to speed things up."
$ylabel = "$N_{\textrm{events}}$"

Allocate plots

$title = "Invisible mass distribution in $e^+e^- \to \nu\bar\nu b \bar b$"
$xlabel = "$M_{\nu\nu}$/GeV"
histogram m_invisible (70 GeV, 130 GeV, 0.5 GeV)

$title = "$bb$ invariant mass distribution in $e^+e^- \to \nu\bar\nu b \bar b$"
$xlabel = "$M_{b\bar b}$/GeV"
histogram m_bb (70 GeV, 130 GeV, 0.5 GeV)

Define the analysis set-up:

analysis = record m_invisible (eval M [n,N]);
           record m_bb (eval M [b,B])

Luminosity and simulation:

luminosity = 10

simulate (nnbb) 

Some more plots and simulations:

$title = "Dijet invariant mass distribution in $e^+e^- \to q \bar q b \bar b$"
$xlabel = "$M_{q\bar q}$/GeV"
histogram m_jj (70 GeV, 130 GeV, 0.5 GeV)

simulate (qqbb) { analysis = record m_jj (eval M / 1 GeV [combine [q,Q]]) }

Perform the analysis:

compile_analysis { $out_file = "lep_higgs.dat" }