A posteriori inclusion of parton density functions in NLO QCD final-state calculations at hadron colliders: the APPLGRID project

A method to facilitate the consistent inclusion of cross-section measurements based on complex final-states from HERA, TEVATRON and the LHC in proton parton density function (PDF) fits has been developed. This can be used to increase the sensitivity of LHC data to deviations from Standard Model predictions. The method stores perturbative coefficients of NLO QCD calculations of final-state observables measured in hadron colliders in look-up tables. This allows the a posteriori inclusion of parton density functions (PDFs), and of the strong coupling, as well as the a posteriori variation of the renormalisation and factorisation scales in cross-section calculations. The main novelties in comparison to original work on the subject are the use of higher-order interpolation of Lagrangian form, which substantially improves the trade-off between accuracy and memory use, and a CPU and computer memory optimised way to construct and store the look-up table using modern software tools. It is demonstrated that a sufficient accuracy on the cross-section calculation can be achieved with reasonably small look-up table size by using the examples of jet production and electro-weak boson (Z, W) production in proton-proton collisions at a center-of-mass energy of 14 TeV at the LHC. The use of this technique in PDF fitting is demonstrated in a PDF-fit to HERA data and simulated LHC jet cross-sections as well as in a study of the jet cross-section uncertainties at various centre-of-mass energies.

[1]  M. Cacciari,et al.  The Catchment Area of Jets , 2008, 0802.1188.

[2]  N. Cabibbo.  Unitary Symmetry and Leptonic Decays , 1963 .

[3]  Wu-Ki Tung,et al.  Inclusive jet production, parton distributions, and the search for new physics , 2003 .

[4]  G. Salam,et al.  A Practical Seedless Infrared Safe Cone Algorithm a , 2007, 0705.2696.

[5]  A. Martin,et al.  Parton distributions for the LHC , 2009, 0901.0002.

[6]  M. Botje.  Error estimates on parton density distributions , 2001, hep-ph/0110123.

[7]  Z. Trocsanyi,et al.  Multijet cross sections in deep inelastic scattering at next-to-leading order. , 2001, Physical review letters.

[8]  G. Zanderighi,et al.  Accurate QCD predictions for heavy-quark jets at the Tevatron and LHC , 2007, 0704.2999.

[9]  Higher-order corrections to jet cross sections in hadron colliders , 1993, hep-ph/9302225.

[10]  Richard D. Ball,et al.  A determination of parton distributions with faithful uncertainty estimation , 2009 .

[11]  Hayes,et al.  Review of Particle Physics. , 1996, Physical review. D, Particles and fields.

[12]  J. Huston,et al.  Hard interactions of quarks and gluons: a primer for LHC physics , 2006, hep-ph/0611148.

[13]  Helmuth Spieler,et al.  Big Bang Nucleosynthesis (in "The Review of Particle Properties" 2004) , 2004, astro-ph/0406663.

[14]  Makoto Kobayashi,et al.  CP Violation in the Renormalizable Theory of Weak Interaction , 1973 .

[15]  W. Vogelsang,et al.  Towards a global analysis of polarized parton distributions , 2001, hep-ph/0107064.

[16]  G. G. Stokes.  "J." , 1890, The New Yale Book of Quotations.

[17]  R. K. Ellis,et al.  Radiative corrections to Zb{bar B} production , 2000 .

[18]  J. Huston,et al.  New generation of parton distributions with uncertainties from global QCD analysis , 2002, hep-ph/0201195.

[19]  R. Ellis,et al.  An update on vector boson pair production at hadron colliders , 1999, hep-ph/9905386.

[20]  Monaco,et al.  An NLO QCD analysis of inclusive cross-section and jet-production data from the ZEUS experiment , 2005 .

[21]  J. Huston,et al.  Implications of CTEQ global analysis for collider observables , 2008, 0802.0007.

[22]  Extracting parton densities from collider data , 1997, hep-ph/9708392.

[23]  Juan Rojo,et al.  A Higher Order Perturbative Parton Evolution Toolkit (HOPPET) , 2008, Comput. Phys. Commun..

[24]  Z. Nagy,et al.  Three-jet cross sections in hadron-hadron collisions at next-to-leading order. , 2002, Physical review letters.

[25]  Z. Nagy,et al.  Next-to-leading order calculation of three jet observables in hadron hadron collision , 2003 .