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NNLL-fast

NNLL-fast is a computer program which computes the squark and gluino hadroproduction cross sections including approximate next-to-next-to-leading order (NNLOApprox) supersymmetric QCD corrections and the resummation of soft gluon emission at next-to-next-to-leading-logarithmic (NNLL) accuracy, including the resummation of Coulomb gluons with a NLO Coulomb potential and bound-state contributions below the production threshold. NNLL-fast also provides an estimate of the theoretical uncertainty due to scale variation, the parton distribution functions, and the value of the strong coupling αs. The program reads in grid files with NLO and NNLOApprox+NNLL results, the scale uncertainty and the PDF and αs error and uses a fast interpolation routine to provide predictions for any value of squark and gluino masses in the mass ranges specified below. The results are provided for the LHC collision energy of 13 TeV, and will be updated for future runs of the LHC. The predictions are created with the recent PDF4LHC15_MC PDF sets.

NNLL-fast is the successor to NLL-fast, the code which provided predictions at NLO+NLL accuracy for squark and gluino production with previous generations of PDF sets.

NEW: A separate version to calculate scalar leptoquark pair-production, NNLL-fast-LQ, at NLO+NNLL accuracy is now also available.

NNLL-fast is based on results obtained by many authors over the years. In alphabetical order, the contributions were provided by: Wim Beenakker, Silja Brensing-Thewes, Christoph Borschensky, Michael Krämer, Anna Kulesza, Leszek Motyka, Eric Laenen and Irene Niessen. Additionally, NNLL-fast uses NLO results obtained with Prospino. Therefore we ask to cite the following papers when referring to NNLL-fast:

Squark and gluino production:

Stop (sbottom) production:

Scalar Leptoquark pair production:

NLO cross sections with t-channel are calculated with the help of MadGraph5_aMC@NLO, please cite

NEW: NNLL-fast-LQ (LHC @ 13 TeV)

  • Main program and grids in one package for calculation of NLO(QCD)+NNLL nnllfast-LQ.
  • The output can also be used to calculate full NLO (including t-channel contributions) + NNLL.

NNLL-fast, version 1.1 (LHC @ 13 TeV)

  • Main program and grids in one package nnllfast-1.1.
  • The package consists of NNLL-fast version 1.0 package, extended by results for squark production in the large gluino mass limit and gluino production in the large squark mass limit (decoupled cases).

NNLL-fast, version 1.0 (LHC @ 13 TeV)

  • Main program and grids in one package nnllfast-1.0.
  • Upon request, the process of gluino pair-production is also available for gluino masses ranging from 100 to 200 GeV and squark masses ranging from 500 to 3000 GeV.
  • The theoretical scale uncertainty is determined from the variation of the total cross section when simultaneously varying the renormalisation, factorisation, Coulomb, and Bohr scales around their respective central values up and down by a factor of 2.
  • Please note that the the PDF and αs uncertainties are given as the combined uncertainty from the quadratic sum of the two.
  • For grids for stop production, the light flavour squarks and the heavy stop-2 are considered as very heavy, while the stop mixing angle corresponds to CMSSM benchmark point 40.2.5 as defined in arXiv:1109.3859. Additionally, we provide a parametrisation error for the total cross section when varying the stop mixing angle in the range $-1 \le \sin 2\theta_{\tilde{t}} \le +1$.

NNLL-fast-LQ is a python script that runs with python 2.7.X or python 3 with numpy and scipy.

NNLL-fast is written in the Fortran programming language, so most Fortran compilers should be able to compile the code. One that it has been tested with is the free GNU Fortran compiler gfortran. On a Linux terminal, the command to compile the code is:

$ gfortran nnllfast.f -o name_of_the_executable

where nnllfast.f has to be replaced by the correct Fortran source file, depending on the version of NNLL-fast.

NNLL-fast-LQ: can be used in two different ways. NNLLfast_LQ.py can be executed with command line arguments:

$ python NNLLfast_LQ.py PDF m

Here PDF is the parton distribution function and can be either NNPDF31 or CT18. m is the leptoquark mass in GeV between 500 GeV and 2300 GeV. The output is in this case written on screen. NNLLfast_LQ.py can also be executed without command line arguments:

$ python NNLLfast_LQ.py

In this case the script uses PDF and masses, which are defined in the script NNLLfast_LQ.py. The default values can be edited to obtain the output for a list of masses between 500 GeV and 2300 GeV. The output is written in a file with default name output.out.

NNLL-fast: After compiling nnllfast.f, it should be called in the following way for all four squark and gluino production processes:

$ ./name_of_the_executable process squark_mass gluino_mass

or, for the case of stop-antistop (sbottom-antisbottom) production:

$ ./name_of_the_executable st stop_mass gluino_mass

The command line attribute process can take the following values:

sb     squark-antisquark production,
ss     squark-squark production,
gg     gluino-gluino production,
sg     squark-gluino production.

Ranges of gluino and squark masses (squark_mass, gluino_mass, stop_mass) are:

for gluino-pair production:
   500 GeV  <= gluino mass <= 3000 GeV    and   500 GeV <= squark mass <= 3000 GeV,
for squark-gluino  production:
   500 GeV  <= gluino mass <= 3000 GeV    and   500 GeV <= squark mass <= 3000 GeV,
for squark-antisquark and squark-pair production:
   500 GeV  <= squark mass <= 3000 GeV    and   500 GeV <= gluino mass <= 3000 GeV
and for stop-antistop production:
   100 GeV  <=  stop mass  <= 3000 GeV    and   500 GeV <= gluino mass <= 5000 GeV 
   (other SUSY parameters: light flavour squark and stop 2 masses considered as very heavy,
                           and stop mixing angle according to CMSSM benchmark 
                           point 40.2.5 as defined in arXiv:1109.3859.)  

NNLL-fast-LQ:

NNLLfast output for leptoquark pair production
LHC @ 13 TeV, NNPDF31
mLQ = 1000.0 GeV
NLO(QCD) = 5.237E-03 + 6.049E-04 - 7.102E-04 +- 1.990E-04 pb
NLO(QCD)+NNLL = 5.436E-03 + 2.302E-05 - 2.302E-05 +- 2.011E-04 pb
delta NNLL(mu=m) = 5.221E-04 pb
delta NNLL(mu=m/2) = 1.912E-05 pb
delta NNLL(mu=2m) = 1.201E-03 pb

NNLL-fast:

# LHC @ 13 TeV, NNLO PDF4LHC15 (NLO PDF4LHC15 for NLO)
# process: sg   
# ms[GeV]  mg[GeV]   NLO[pb]     NNLL+NNLO_app[pb]   d_mu+[%]    d_mu-[%]   d_pdfas+[%]  d_pdfas-[%]  K_NNLL
--------------------------------------------------------------------------------------------------------------
  1700.    2100.    0.479E-02       0.613E-02          3.92       -5.87      11.88       -11.88        1.28

The previous versions of NLL-fast can be downloaded from here.

If you have questions, comments, or want to report a problem regarding the code, please contact Anna Kulesza or Christoph Borschensky.

  • start.txt
  • Last modified: 2020/10/05 11:00
  • by Daniel Schwartländer