Unfolding

Distributions f(x) measured in high-energy-physics experiment are often distorted or transformed by limited acceptance and finite resolution of the detector. The unfolding of measured distribution is an important, but due to the inherent instability a very difficult problem. A talk about unfolding has been given in the 1984 CERN Summer School for Computing in Aiguablava, Spain (CERN Yellow Report 85-02), and DESY 84-118 (Red Report).

The manual and the source code of the unfolding program RUN, written in Fortran77, is available below. Input to the unfolding program are ntuples for data and Monte Carlo quantities. The unfolded distribution f(x) is reconstructed in bins by a regularization method, which includes the determination of the covariance matrix by error propagation from the data statistics and the properties of the resolution function.

There is of course no guarantee that the program is working correctly. The program has been developed about 15 years ago for the use by the author. Its usage requires some understanding of unfolding and statistics in general, especially with respect to the optimization of the various parameters.

A new version, with automatic optimization of the various parameters, is being developled, but will not be released.

Contributions to the Conference on Adcanced Statistical Techniques in Particle Physics, Durham, 18 - 22 March 2002: ps-file: A new method for the high-precision alignment of track detectors - ps-file: An unfolding method for high energy physics experiments

Talks (and a note)

Talk about Unfolding at ZEUS 1997: psfile psfile/2

Talk about Unfolding at CERN/Lep 2000: psfile psfile/2

Talk about Unfolding at ZEUS 2000: psfile psfile/2

Unfolding for HEP experiments - Introduction to inverse problems; DESY Computing Seminar 23.rd June 2008 pdf-file

Notes about RUN by Glen Cowan: psfile

Paper

An unfolding method for high energy physics experiments, Contribution to the Conference on Adcanced Statistical Techniques in Particle Physics, Durham, 18 - 22 March 2002 ps-file
and hep-ex/0208022.pdf pdf-file

Manual: psfile

Fortran77 Source files

There are 16 source files with Fortran programs. Some source files are specific for the RUN program, others contain utility routines (not all of the utility routines in the source file are used in RUN).

MAIN test program and dummy XFUNCT function source
subprograms for example job source
basic subprograms of the unfolding program source
ntuple IO subprograms source
random number generators source
smoothing package source
subprogram for minimization in 1 dimension source
matrix operations source
histogram utilities source
printer plot subprograms source
cubic B-splines subprograms source
cubic splines subprogram source
print utilities source
text handling subprograms source
graphics output subprograms (LOOK) source
graphics output subprograms (PAW) source

The software can be freely used for research and education. We expect that all publications describing work using this software quote at least one of the references below.

The RUN manual
Regularized Unfolding for High-Energy Physics Experiments, OPAL Technical Note TN361, March 8, 1996
1984 CERN Summer School for Computing in Aiguablava, Spain (CERN Yellow Report 85-02)
DESY 84-118 (Red Report)

Disclaimer: This software is provided without any expressed or implied warranty. In particular thre is no warranty of any kind concerning the fitness of this software for any particular purpose.