May 13 – 19, 2018
Venice, Italy
Europe/Zurich timezone
The organisers warmly thank all participants for such a lively QM2018! See you in China in 2019!

Centrality and impact parameter in nucleus-nucleus collisions

May 16, 2018, 3:20 PM
Sala Perla, 1st Floor (Palazzo del Casinò)

Sala Perla, 1st Floor

Palazzo del Casinò

Parallel Talk Correlations and fluctuations Correlations and fluctuations


Jean-Yves Ollitrault (CNRS)


In heavy-ion collision experiments, the centrality of a collision is defined according to the transverse energy or number of tracks observed in a given detector. We propose a procedure to relate this experiment-defined centrality to the true centrality of the collision, defined according to impact parameter, in a way which does not need require the introduction of a Glauber model or the concept of participant nucleons. Our method allows to accurately reconstruct the probability distribution of impact parameter at a fixed value of the experiment-defined centrality, up to 5%. We argue that in central collisions, the fluctuations of impact parameter have specific signatures in the centrality dependence of the cumulants of elliptic flow, $v_2\{2\}$ and $v_2\{4\}$, and that these effects are clearly visible in experimental data.
Extension to proton-nucleus collisions is discussed (work in progress).

[Based on arXiv:1708.00081]

Content type Theory
Centralised submission by Collaboration Presenter name already specified

Primary author


Giuliano Giacalone (Université Paris-Saclay)

Presentation materials