Evidence of shadowing in inelastic nucleon-nucleon cross section

Jun 2, 2020, 12:00 PM


Oral Presentation Electroweak Probes Parallel


Mr Mikko Kuha (University of Jyväskylä)


The Glauber modeling plays a key role in centrality-dependent measurements of heavy-ion collisions.
A central input parameter in Glauber models is the inelastic nucleon-nucleon cross section $\sigma_{\rm nn}^{\rm inel}$ which is nearly always taken from proton-proton measurements. At the LHC energies $\sigma_{\rm nn}^{\rm inel}$ depends on the QCD dynamics at small $x$ and low interaction scales where the shadowing/saturation phenomena are expected to become relatively more important for larger nuclei than proton. Thus, $\sigma_{\rm nn}^{\rm inel}$ e.g. in Pb+Pb collisions may well be lower than what is seen in proton-proton collisions.

In this talk we demonstrate how to use the recent $W^\pm$ and $Z$ measurements as a "standard candle" to extract $\sigma_{\rm nn}^{\rm inel}$ in Pb+Pb collisions. Our analysis -- built on the ATLAS data, state-of-the-art NNLO QCD calculations and nuclear PDFs -- indicate that at the LHC energies $\sigma_{\rm nn}^{\rm inel}$ in Pb+Pb collisions is suppressed relative to the proton-proton measurements by tens of percents. We demonstrate that this is in line with expectations from nuclear PDFs.

Track Electroweak Probes
Contribution type Contributed Talk

Primary authors

Mr Mikko Kuha (University of Jyväskylä) Kari J. Eskola (University of Jyvaskyla) Dr Ilkka Helenius (University of Jyväskylä) Hannu Paukkunen (University of Jyväskylä)

Presentation materials