Inclusive $ψ(2S)$ production at midrapidity in pp collisions at $\sqrt{s} = 13$ TeV

Abstract

Inclusive production of $ψ(2S)$ mesons is measured for the first time at midrapidity ($|y| < 0.9$) in pp collisions at $\sqrt{s} = 13$ TeV using the ALICE detector at the LHC. The measurement is performed in the transverse-momentum ($p_{\rm T}$) range of 4 to 16 GeV/$c$ and is based on events triggered by the Transition Radiation Detector, corresponding to an integrated luminosity of $1.7 \pm 1.8\%$ (syst.) pb$^{-1}$. The $p_{\rm T}$-differential production cross section of the $ψ(2S)$ and its ratio to the J/$ψ$ production cross section are presented. The results extend the accessible $p_{\rm T}$ range down to 4 GeV/$c$, and a mild rise of the $ψ(2S)$-to-J/$ψ$ cross section ratio with increasing $p_{\rm T}$ is observed. The measurements are compared with theoretical predictions based on NRQCD and the ICEM model.

Figures (7)

• Figure 1: Acceptance times TRD-trigger efficiency ($\epsilon_{\mathrm{TRD}}(p_{\mathrm{T}}^{\mathrm{e}})$) described by Eq. \ref{['eq:slEff']} for single electrons (left) and positrons (right) obtained from TRD-triggered data (red solid circle), fitted with an error function (red line), and MC simulation (black open circle). See text for details.
• Figure 2: Invariant-mass distributions of $\rm e^{+}e^{-}$ pairs in the same event for the lowest (left) and the highest (right) $p_{\rm T}^{\mathrm{ee}}$ intervals. Superimposed to the data are the fits containing the signals of $\mathrm{J/\psi}$ and $\mathrm{\psi(2S)}$ and the correlated (blue area) and uncorrelated (gray area) background sources (see text).
• Figure 3: Acceptance and efficiency as a function of $p_{\rm T}^{\mathrm{ee}}$ for inclusive $\mathrm{J/\psi}$ (left) and $\mathrm{\psi(2S)}$ (right). In addition to the total efficiency, its individual contributions are shown.
• Figure 4: $p_{\rm T}$-differential inclusive $\mathrm{\psi(2S)}$ production cross section at midrapidity in pp collisions at $\sqrt{s}~=~13$ TeemV. Statistical and systematic uncertainties are shown as error bars and boxes, respectively, and data points are plotted according to the Lafferty–Wyatt prescription Lafferty:1994cj. The data points for the inclusive production are obtained by summing the published prompt and non-prompt measurements ATLAS:2023qnh. The statistical and systematic uncertainties are combined in quadrature. Uncertainties related to integrated luminosity are not shown.
• Figure 5: $p_{\rm T}$-differential inclusive $\mathrm{\psi(2S)}$ production cross section at midrapidity in pp collisions at $\sqrt{s}~=~13$ TeemV is compared with ALICE results at forward rapidity ALICE:2017leg (left) and with the model calculations from ICEM icem and NRQCD nrqcd (right). Both calculations include a non-prompt contribution from beauty-hadron decays via FONLL fonll. Data points are plotted according to the Lafferty–Wyatt prescription Lafferty:1994cj. The lower panels show the ratios of the data points or model calculations to the power-law fit to the midrapidity data.