# Production of $\pi^0$ and $\eta$ mesons up to high transverse momentum in pp collisions at 2.76 TeV

## TL;DR

This paper reports measurements of neutral pion and eta meson production at high transverse momentum in proton-proton collisions at 2.76 TeV, using novel analysis techniques to extend the $p_T$ range and compare with theoretical models.

## Contribution

It introduces a new shower-shape based method for identifying high-$p_T$ neutral pions and provides extensive data for testing perturbative QCD calculations.

## Key findings

- Cross sections follow a power-law with exponent ~6.3.
- NLO pQCD calculations underestimate data by 30-50%.
- PYTHIA 8.2 simulations agree within 10-30% at high $p_T$.

## Abstract

The invariant differential cross sections for inclusive $\pi^{0}$ and $\eta$ mesons at midrapidity were measured in pp collisions at $\sqrt{s}=2.76$ TeV for transverse momenta $0.4<p_{\rm T}<40$ GeV/$c$ and $0.6<p_{\rm T}<20$ GeV/$c$, respectively, using the ALICE detector. This large range in $p_{\rm T}$ was achieved by combining various analysis techniques and different triggers involving the electromagnetic calorimeter (EMCal). In particular, a new single-cluster, shower-shape based method was developed for the identification of high-$p_{\rm T}$ neutral pions, which exploits that the showers originating from their decay photons overlap in the EMCal. The measured cross sections are found to exhibit a similar power-law behavior with an exponent of about $6.3$. Next-to-leading-order perturbative QCD calculations differ from the measured cross sections by about $30$% for the $\pi^0$, and between $30$-$50$% for the $\eta$ meson, while generator-level simulations with PYTHIA 8.2 describe the data to better than $10$-$30$%, except at $p_{\rm T}<1$ GeV/$c$. The new data can therefore be used to further improve the theoretical description of $\pi^{0}$ and $\eta$ meson production.