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Neutral pion and $\eta$ meson production in p-Pb collisions at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV

The ALICE collaboration
No Journal Information, 2018

Abstract
Neutral pion and $\eta$ meson invariant differential yields were measured in non-single diffractive p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV with the ALICE experiment at the CERN LHC. The analysis combines results from three complementary photon measurements, utilizing the PHOS and EMCal calorimeters and the Photon Conversion Method. The invariant differential yields of $\pi^0$ and $\eta$ meson inclusive production are measured near mid-rapidity in a broad transverse momentum range of $0.3<p_{\rm T}< 20$ GeV/$c$ and $0.7<p_{\rm T}<20$ GeV/$c$, respectively. The measured $\eta$/$\pi^{0}$ ratio increases with $p_{\rm T}$ and saturates for $p_{\rm T} > 4$ GeV/$c$ at $0.483\pm 0.015_{\rm stat}\pm 0.015_{\rm sys}$. A deviation from $m_{\rm T}$ scaling is observed for $p_{\rm T}<2$ GeV/$c$. The measured $\eta$/$\pi^{0}$ ratio is consistent with previous measurements from proton-nucleus and pp collisions over the full $p_{\rm T}$ range. The measured $\eta$/$\pi^{0}$ ratio at high $p_{\rm T}$ also agrees within uncertainties with measurements from nucleus-nucleus collisions. The $\pi^0$ and $\eta$ yields in p-Pb relative to the scaled pp interpolated reference, $R_{\rm pPb}$, are presented for $0.3<p_{\rm T}<20$ GeV/$c$ and $0.7<p_{\rm T}< 20$ GeV/$c$, respectively. The results are compared with theoretical model calculations. The values of $R_{\rm pPb}$ are consistent with unity for transverse momenta above 2 GeV/$c$. These results support the interpretation that the suppressed yield of neutral mesons measured in Pb-Pb collisions at LHC energies is due to parton energy loss in the hot QCD medium.

  • Table 1

    Data from Figure 5 (left)

    10.17182/hepdata.83700.v1/t1

    Invariant differential yield of PI0 produced in NSD p-Pp collisions with centre-of-mass energy/nucleon 5.02 TeV.

  • Table 2

    Data from Figure 5 (left)

    10.17182/hepdata.83700.v1/t2

    Invariant differential yields of ETA produced in NSD p-Pb collisions with centre-of-mass energy/nucleon 5.02 TeV.

  • Table 3

    Data from Figure 7 (left)

    10.17182/hepdata.83700.v1/t3

    The measured ratio of invariant yields for inclusive ETA to PI0 production at a centre-of-mass energy/nucleon 5.02 TeV.

  • Table 4

    Data from Figure 7 (right)

    10.17182/hepdata.83700.v1/t4

    Ratio of the measured ETA to PI0 ratio to the one obtained via m_T scaling in NSD p-Pb collisions with...

  • Table 5

    Data from Figure 8 (left)

    10.17182/hepdata.83700.v1/t5

    The nuclear modification factor RPPB of PI0 as a function of pT in NSD p-Pb collisions with centre-of-mass energy/nucleon=5.02 TeV,...

  • Table 6

    Data from Figure 8 (right)

    10.17182/hepdata.83700.v1/t6

    The nuclear modification factor RPPB of ETA as a function of pT in NSD p-Pb collisions with centre-of-mass energy/nucleon=5.02 TeV,...

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