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

Abstract

The momentum-differential invariant cross sections of $\ddot{I}{€}^0$ and $\hat{I}\cdot$ 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 $\ddot{I}{€}^0$ and $\hat{I}\cdot$, 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 $\ddot{I}{€}^0$ 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 $\ddot{I}{€}^0$ 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 $\ddot{I}{€}^0$ and are not able to describe the shape and magnitude of the $\hat{I}\cdot$ spectrum. The charged-particle multiplicity dependent $\ddot{I}{€}^0$ and $\hat{I}\cdot$ $p_{\mathrm{T}}$ 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 $\hat{I}\cdot /\ddot{I}{€}^0$ 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 $\ddot{I}{€}^0$ spectrum.

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

Cited by in corpus (1)

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