Example: Z' Search at LHC

Choose the model

model = Zprime

Setup aliases for partons (quarks and gluons) and leptons (electrons and positrons)

alias pr = u:d:s:c:gl:U:D:S:C
alias lepton = e1:E1

Look at e+e--pairs created by colliding all possible parton pairs

process zp_drell_yan = pr, pr => e1, E1

Set values for the model parameters (mass and width of the Z', and set masses of particles summed over to zero)

mZH = 1500 GeV
wZH = 50 GeV
ms = 0
mc = 0

Define reasonable cuts

cuts = all Pt >= 50 GeV [lepton]
       and all -2.5 <= Eta <= 2.5 [e1:E1]
       and all M >= 800 GeV [e1,E1]

Define the process scale

scale = 1500 GeV

Set up the beams (full energy LHC with default lhapdf structure functions

sqrts = 14 TeV
beams = p,p => lhapdf

Integrate the cross sections in order to initialize the phase space grids for similation

integrate (zp_drell_yan) { iterations = 6:20000 }

Choose weighted events for smoother histograms

?unweighted = false

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

$description =
  "A WHIZARD 2.0 Example.
   Cuts: $p_T^\ell\ge50 \textrm{ GeV}$, $M_{\ell\ell} \ge$800 GeV, 
         $|\eta(\ell)|\le2.5$
         \newline Using weighted events to produce smooth 
   distributions."
$ylabel = "$N_{\textrm{events}}$"

Allocate plots

$title = "$Z'$ Drell-Yan dilepton peak $pp\to \ell\ell$"
$xlabel = "$\theta^{\ell}$/GeV"
histogram m_lepton (1 TeV, 2 TeV, 50 GeV)

$title = "$Z'$ Drell-Yan: $p_T$ distribution of the $\ell$"
$xlabel = "$p_T^{\ell}$/GeV"
histogram pt_lepton (100 GeV, 2000 GeV, 100 GeV)

$title = "$Z'$ Drell-Yan: Angular distribution of the $\ell$"
$xlabel = "$\theta^{\ell}$/rad"
histogram th_lepton (0, 3.1415, 0.157)

and tell WHIZARD what to store in them

analysis = record m_lepton (eval M [e1,E1]) and
           record pt_lepton (eval Pt [e1]) and
           record th_lepton (eval Theta [e1]) 

Simulate 100000 events

n_events = 100000
simulate (zp_drell_yan)

and write results to file (and run LaTeX to produce plots etc.)

write_analysis
compile_analysis { $out_file = "Zprime.dat" }

WHIZARD will produce histograms in the ​PDF output and as ​data file. The progress can be monitored on the terminal and in the ​WHIZARD log file.