Eur. Phys. J. C 70, 503-511 (2010)
https://doi.org/10.1140/epjc/s10052-010-1464-6

A method for tuning parameters of Monte Carlo generators and its application to the determination of the unintegrated gluon density

¹ Dipartimento di Fisica Nucleare e Teorica, Università di Pavia, and INFN, Sezione di Pavia, via Bassi 6, 27100, Pavia, Italy
² Deutsches Elektronen-Synchroton DESY, Notkestrasse 85, 22603, Hamburg, Germany
³ Departement Fysica, Universiteit Antwerpen (CGB), Groenenborgerlaan 171, 2020, Antwerpen, Belgium

alessandro.bacchetta@unipv.it

Received: 1 February 2010
Revised: 6 August 2010
Published online: 12 October 2010

Abstract

A method for tuning parameters in Monte Carlo generators is described and applied to a specific case. The method works in the following way: each observable is generated several times using different values of the parameters to be tuned. The output is then approximated by some analytic form to describe the dependence of the observables on the parameters. This approximation is used to find the values of the parameter that give the best description of the experimental data. This results in significantly faster fitting compared to an approach in which the generator is called iteratively. As an application, we employ this method to fit the parameters of the unintegrated gluon density used in the CASCADE Monte Carlo generator, using inclusive deep inelastic data measured by the H1 Collaboration. We discuss the results of the fit, its limitations, and its strong points.