Introduction

Proton-nucleus (pA) collisions are an important tool for the study of strongly interacting matter and the Quark–Gluon Plasma (QGP), complementing and extending measurements carried out with high energy collisions of heavy nuclei [1]. By using a proton instead of a heavy nucleus as one of the projectiles, measurements of pA collisions have unique sensitivity to the initial-state nuclear wave function, and can elucidate the effects of cold nuclear matter on a wide range of observables of the QGP [2, 3].

Measurements of inclusive distributions of hadrons at mid-rapidity at the LHC probe parton fractional momentum x in the range \(10^{-4}<x<10^{-2}\), where nuclear modification to hadronic structure is expected to be sizable [2]. This range extends an order of magnitude smaller in x with respect to other colliders. Inclusive hadron measurements are also essential to constrain theoretical models of particle production ([4] and references therein).

Within the framework of collinearly-factorized perturbative QCD (pQCD), effects of the nuclear environment are parameterized using nuclear-modified parton distribution functions (nPDFs) [5,6,7,8,9,10], which have been determined from global fits at next-to-leading order (NLO) to data from deep inelastic scattering (DIS), Drell–Yan, and \(\pi ^{0}\) production. Inclusive hadron measurements at the LHC provide new constraints on gluon nPDFs [5, 9, 11], and the flavor dependence of sea-quark nPDFs [12]. Hadron production measurements at the LHC are likewise needed to improve constraints on fragmentation functions (FFs) [13,14,15].

An alternative approach to the theoretical description of hadronic structure is the Color Glass Condensate (CGC) [16], an effective theory for the nuclear environment at low x where the gluon density is high and non-linear processes are expected to play a significant role. CGC-based calculations successfully describe measurements of particle multiplicities and inclusive hadron production at high \(p_{\mathrm{T}}\) in pp, d−Au and p–Pb collisions at RHIC and at the LHC [17,18,19]. CGC calculations, with parameters fixed by fitting to DIS data, have been compared to particle distributions at hadron colliders, thereby testing the universality of the CGC description [19]. Additional measurements of inclusive hadron production at the LHC will provide new constraints on CGC calculations, and help to refine this theoretical approach.

Recent measurements of p–Pb collisions at the LHC indicate the presence of collective effects in such systems, which influence inclusive hadron distributions [3, 20,21,22,23,24,25]. Detailed study of identified particle spectra over a broad \(p_{\mathrm{T}}\) range can constrain theoretical models incorporating such effects. For example, the EPOS3 model [26] requires the inclusion of collective radial flow in p–Pb collisions to successfully describe the \(p_{\mathrm{T}}\) spectrum of charged pions, kaons, protons, \(\Lambda \) and \(\Xi \) baryons [27, 28]. Tests of this model with neutral pions and \(\eta \) mesons will provide additional constraints to this approach.

The shape of the invariant production cross section of various hadron species in pp collisions can be approximated by a universal function of \(m_{\mathrm{T}} =\sqrt{p_{\mathrm{T}} ^2+M^2}\) (“\(m_{\mathrm{T}}\) scaling”) [29] where M is the hadron mass. This scaling has been tested with many different collision energies and systems [30,31,32], and is commonly utilized to calculate hadronic distributions in the absence of measurements. Violation of \(m_{\mathrm{T}}\) scaling at low \(p_{\mathrm{T}}\) in pp collisions at the LHC has been observed for \(\pi ^{0}\) and \(\eta \) mesons at \(\sqrt{s}\)  = 7 TeV [33], and at \(\sqrt{s}\)  = 8 TeV  [34]; this may arise from collective radial flow that is indicated in pp collisions for \(\sqrt{s}>0.9~\hbox {TeV}\) [35]. However, a deviation from \(m_{\mathrm{T}}\) scaling at very low \(p_{\mathrm{T}}\) has also been observed in pA collisions at \(\sqrt{s_{\mathrm{NN}}}\)  = 29.1 GeV [36], where it was attributed to enhanced low \(p_{\mathrm{T}}\) pion production from resonance decays. The simultaneous measurement of \(\pi ^{0}\) and \(\eta \) mesons over a broad \(p_{\mathrm{T}}\) range is therefore important to explore the validity of \(m_{\mathrm{T}}\) scaling in pA collisions. Precise measurements of \(\pi ^{0}\) and \(\eta \) mesons at low \(p_{\mathrm{T}}\) also provide an experimental determination of the background for measurements of dilepton and direct photon production [37, 38].

Strong suppression of inclusive hadron yields at high \(p_{\mathrm{T}}\) has been observed in heavy-ion collisions at RHIC [