# 10th International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions

May 31, 2020 to June 5, 2020
Online
US/Central timezone

## Evidence of shadowing in inelastic nucleon-nucleon cross section

Jun 2, 2020, 12:00 PM
20m
https://cern.zoom.us/j/96622048465

#### https://cern.zoom.us/j/96622048465

Oral Presentation Electroweak Probes

### Speaker

Mr Mikko Kuha (University of Jyväskylä)

### Description

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.

Contribution type Contributed Talk Electroweak Probes

### 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)