Light neutral-meson production in pp collisions at $\sqrt{\mathbf{s}}$ = 13 TeV

Abstract

The momentum-differential invariant cross sections of ${\pi }^0$ and $\eta$ mesons are reported for pp collisions at $\sqrt{s}$ = 13 TeV at midrapidity ($|y|<0.8$). The measurement is performed in a broad transverse-momentum range of $0.2<p_{\mathrm{T}}<200$ GeV/$c$ and $0.4<p_{\mathrm{T}}<60$ GeV/$c$ for the ${\pi }^0$ and $\eta$, respectively, extending the $p_{\mathrm{T}}$ coverage of previous measurements. Transverse-mass-scaling violation of up to 60% at low transverse momentum has been observed, agreeing with measurements at lower collision energies. Transverse Bjorken $x$ ($x_{\mathrm{T}}$) scaling of the ${\pi }^0$ cross sections at LHC energies is fulfilled with a power-law exponent of $n=5.01\pm 0.05$, consistent with values obtained for charged pions at similar collision energies. The data are compared to predictions from next-to-leading order perturbative QCD calculations, where the ${\pi }^0$ spectrum is best described using the CT18 parton distribution function and the NNFF1.0 or BDSS fragmentation function. Expectations from PYTHIA8 and EPOS LHC overestimate the spectrum for the ${\pi }^0$ and are not able to describe the shape and magnitude of the $\eta$ spectrum. The charged-particle multiplicity dependent ${\pi }^0$ and $\eta$ $p_{\mathrm{T}}$ spectra show the expected change of the spectral shape, characterized by a flatter slope with increasing multiplicity. This is demonstrated across a broad transverse-momentum range and up to events with a charged-particle multiplicity exceeding five times the mean value in minimum bias collisions. The $\eta /{\pi }^0$ ratio depends on the charged-particle multiplicity for $p_{\mathrm{T}}<4$ GeV/$c$. PYTHIA8 and EPOS LHC qualitatively explain this behavior with an increasing contribution from the feed-down of heavier particles to the ${\pi }^0$ spectrum.

39 pages, 13 captioned figures, 9 tables, authors from page 33, figures at http://alice-publications.web.cern.ch/node/11738

References in corpus (29)

• An Introduction to PYTHIA 8.2
• A New Method for Combining NLO QCD with Shower Monte Carlo Algorithms
• Matching NLO QCD computations with Parton Shower simulations: the POWHEG method
• New parton distribution functions from a global analysis of quantum chromodynamics
• EPOS LHC : test of collective hadronization with LHC data
• Tuning PYTHIA 8.1: the Monash 2013 Tune
• Performance of the ALICE Experiment at the CERN LHC
• The ALICE TPC, a large 3-dimensional tracking device with fast readout for ultra-high multiplicity events
• QCD and strongly coupled gauge theories: challenges and perspectives
• Parton Ladder Splitting and the Rapidity Dependence of Transverse Momentum Spectra in Deuteron-Gold Collisions at RHIC
• Performance of the ALICE VZERO system
• Alignment of the ALICE Inner Tracking System with cosmic-ray tracks
• Small System Collectivity in Relativistic Hadron and Nuclear Collisions
• Parton-to-Pion Fragmentation Reloaded
• Novel Collective Phenomena in High-Energy Proton-Proton and Proton-Nucleus Collisions
• Constraints from the first LHC data on hadronic event generators for ultra-high energy cosmic-ray physics
• A determination of the fragmentation functions of pions, kaons, and protons with faithful uncertainties
• Hard diffraction in hadron--hadron interactions and in photoproduction
• Effects of Colour Reconnection on Hadron Flavour Observables
• Collectivity and electromagnetic radiation in small systems
• Confronting current NLO parton fragmentation functions with inclusive charged-particle spectra at hadron colliders
• Global Analysis of Fragmentation Functions for Eta Mesons
• Higher-Twist Dynamics in Large Transverse Momentum Hadron Production
• Inclusive Hadron Production in the CERN-LHC Era
• The ALICE Transition Radiation Detector: construction, operation, and performance
• Investigating the inclusive transverse spectra in high-energy $pp$ collisions in the context of geometric scaling framework
• Applicability of transverse mass scaling in hadronic collisions at the LHC
• Predictions on the transverse momentum spectra for charged particle production at LHC-energies from a two component model
• Single-inclusive production of large-pT charged particles in hadronic collisions at TeV energies and perturbative QCD predictions

Cited by in corpus (2)

• Global analysis of fragmentation functions to light neutral hadrons
• Measurement of $\omega$ meson production in pp and p$-$Pb collisions at $\sqrt{{\mathbf{s}}_{\mathrm{NN}}}=5.02$ TeV