The VIRCOL website

=The LHAPDF home page= Theory = LHAPDF ready MC's = Downloads = online manual =


VIRCOL project access (restricted)

For talks about VIRCOL:
Theoretical description: Loopfest03
For a short outline of the VIRCOL parton shower MC: TeaserTalk.ppt

SAMPER project access (restricted)

Monte Carlo downloads

LHAPDF Version 0

(For newer versions:    


The experimental uncertainties in current and future hadronic colliders are decreasing to a level where more careful consideration has to be given to the uncertainties in the theoretical predictions. One important source of these uncertainties has its origin in Parton Density Functions (PDFs). The PDF uncertainties in turn are a reflection of those in the experimental data used as an input to the PDF fits and in the uncertainties of the theoretical calculations used to fit those data.  As a consequence, sophisticated statistical methods and approximations have to be developed to handle the propagation of uncertainties. These methods are discussed in the theory section.

A convenient way of evaluating PDF uncertainties is by expressing the uncertainty in a set of individual PDFs. By evaluating the observable for each of the members of the PDF set the PDF uncertainty can be determined.  The Les Houches Accord Parton Density Functions (LHAPDF) interface package is designed to work with PDF sets.


The Les Houches Accord Parton Density Function interface was conceived at the Les Houches 2001 workshop in the PDF working group to enable the usage of Parton Density Functions with uncertainties in a uniform manner.  When PDFs with uncertainties are considered, a ``fit'' to the data no longer is described by a single PDF. Instead in its most flexible implementation, a fit is represented by a PDF set consisting of many individual PDF members. Calculating the observable for all the PDF members enables one to reconstruct the uncertainty on the observable. The LHAPDF interface was made with this in mind and manipulates PDF sets.

The LHAPDF code and the PDF files can be obtained in the download section.


The LHAPDF interface can be viewed as a successor to PDFLIB and improvements
were added. To list some of the features:

bulletThe handling of PDF sets to enable PDF fits that include uncertainties.
bulletAll PDF sets are defined through external files in parameterized form. This means the files are compact compared to storing the PDFs in a grid format. Also new PDF sets can be defined by constructing the PDF defining files. The actual LHAPDF code does not have to be changed.
bulletThe LHAPDF code is modular and default choices like the QCDNUM evolution code can be easily altered.

The LHAPDF code and the PDF files can be obtained in the download section. Several examples using the LHAPDF code are in the example section.

Comments and/or Problems
=The LHAPDF home page= Theory = LHAPDF ready MC's = Downloads = online manual =