OPUCEM is hosted by Hepforge, IPPP Durham

OPUCEM - Oblique Parameters Using C with Error-checking Machinery

OPUCEM (pronounced ö-peu-gem, with o-umlaut as in French deux) is a C library which combines formulas from a multitude of references for calculating Peskin-Takeuchi parameters S-T-U. The aim is to provide a minimum-dependence code to facilitate the sharing of formulas, such that:

  • Article authors can provide typo-free versions of their formulas that match their published numerical results.
  • Cross-checks are done to compare formulas in different papers directly.
  • Reviews by any interested party is possible.
  • Further studies can refer to a certain version of the code and future errata can easily be done.

We aim to provide extra test functions in our library that does the cross-checking of different formulas - against approximation, against other calculations of the same quantities or against limiting cases of other quantities.

Currently implemented are:

  • new lepton doublets with Dirac-or-Majorana-type neutral leptons
  • new quark doublets
  • SM and 2HDM Higgs boson
  • recalculation of the SM origin in the S-T plane based on reference values of the masses of the top quark and the Higgs boson

References for the current code include:

  • M.S. Chanowitz, Phys. Rev. D79 (2009) 113008
  • H.-J. He, N. Polonsky, S. Su, Phys. Rev. D64 (2001) 053004
  • J.R. Forshaw, D.A. Ross, B.E. White, JHEP0110:007 (2001)
  • A.A. Natale, P.S. Rodriges Da Silva, Mod. Phys. Lett. A10 (1995) 1829
  • B.A. Kniehl, H.-G. Kohrs, Phys. Rev. D48 (1993) 225
  • E. Gates, J. Terning, Phys. Rev. Lett. 67 (1991) 1840

Example driver code to use the library, tools for plotting ST ellipses and (extensive) internal documentation are provided as well. The latest stable tag is opucem-00-00-08.

For a review of OPUCEM and an example of its application, see the talk given at the Second Workshop on Beyond 3 Generation Standard Model in Taipei. You might also have a look at our screenshots page.

If you use OPUCEM or its results,

* please cite the reference paper: Computer Physics Communications 182 (2011), pp. 1732-1743 .
* You can also check and cite this more recent paper: The European Physical Journal C, Volume 72, Issue 4 that can be found here .


* Erkcan Ozcan, University College London - Now at Bogazici University
* Gokhan Unel, University of California, Irvine
emails: name.surname at cern dot ch

Ozgur Cobanoglu, CERN - Now at Sanko (main author of the GUI), Mehmet Sahin, TOBB ETU (5+ generations in the GUI), Emre Celebi, Bogazici University (2HDM in the GUI and cross-checks)

Special thanks to: R. Michael Winters & Deva O'Neil, College of Wooster (Mathematica code for the ST ellipses)