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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.

Last modified 14 years ago Last modified on Apr 7, 2011, 4:32:14 PM

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