Neutron-skin effect and centrality dependence of high-pT observables in nuclear collisions

Apr 13, 2016, 12:20 PM
Auditorium (DESY Hamburg)


DESY Hamburg

Structure Functions and Parton Densities WG1 Structure Functions and Parton Densities


Dr Ilkka Helenius (Lund University)


High-energy nuclear collisions are often classified in terms of centrality. Theoretically the centrality binning is obtained using the Woods-Saxon parametrization for nuclear density as an input for Glauber model. Traditionally the parametrization do not differentiate between protons and neutrons. However, according to measurements in nuclear physics, the density of neutrons decrease slower at the edge of the nuclei than the density of protons. This phenomenon is known as a neutron-skin effect and can have an influence to the centrality dependence of high-pT observables sensitive to electric charge in high-energy nuclear collisions. Potentially the phenomenon could also be measured in e+A collisions if a similar centrality binning can be performed. In this talk we present NLO pQCD predictions for the centrality dependence of the direct photon production at high-pT in Pb+Pb collisions at the LHC applying the neutron-skin effect and spatially dependent nuclear PDFs from EPS09s fit. Furthermore, we discuss about W production and the ratio between positively and negatively charged hadrons. The advantage of these observables would be that the nuclear modifications of the PDFs largely cancel out allowing one to separate these two competing centrality-dependent effects.

Primary author

Dr Ilkka Helenius (Lund University)


Dr Hannu Paukkunen (University of Jyväskylä)

Presentation materials