The $p_{\rm T}$-differential cross section of $\omega$ meson production in pp collisions at $\sqrt{s}$ = 13 TeV at midrapidity ($|y|<~0.5$) was measured with the ALICE detector at the LHC, covering an unprecedented transverse-momentum range of $1.6 <~ p_{\rm T} <~50$ GeV/$c$. The meson is reconstructed via the $\omega\rightarrow\pi^+\pi^-\pi^0$ decay channel. The results are compared with various theoretical calculations: PYTHIA8.2 with the Monash 2013 tune overestimates the data by up to 50%, whereas good agreement is observed with Next-to-Leading Order (NLO) calculations incorporating $\omega$ fragmentation using a broken SU(3) model. The $\omega/\pi^0$ ratio is presented and compared with theoretical calculations and the available measurements at lower collision energies. The presented data triples the $p_{\rm T}$ ranges of previously available measurements. A constant ratio of $C^{\omega/\pi^0}=0.578\pm0.006~\text{(stat.)}\pm 0.013~\text{(syst.)}$ is found above a transverse momentum of 4 GeV/$c$, which is in agreement with previous findings at lower collision energies within the systematic and statistical uncertainties.
Submitted to: JHEP
e-Print: arXiv:2411.09432 | PDF | inSPIRE
CERN-EP-2024-303
Figure group
Figure 1
Invariant mass distributions of $\pi^+\pi^-\pi^0$ candidates shown in the vicinity of the nominal $\omega$ mass in exemplary $p_{\rm T}$ intervals. Each panel displays a different $\pi^0$ reconstruction method, which is indicated in the respective panel and described in the text. A third-order polynomial is used to describe the background, which is subtracted from the distribution and the obtained signal is fitted with a Gaussian with two exponential tails. The integration range used to obtain the raw yields via bin-by-bin counting is indicated by vertical gray lines. |      |
Figure 3
Ratios of the $\omega$ production cross section obtained using five different $\pi^0$ reconstruction methods with respect to a Levy--Tsallis fit of the combined measurement. The fit parameters are given in Table 2, together with the reduced $\chi^2$ of the converged fit. The statistical and systematic uncertainties of the individual measurements are given in Table 1 and are represented by vertical bars and boxes, respectively. |  |
Figure 4
Invariant cross section of $p+p\rightarrow\omega+X$ production at midrapidity in pp collisions at $\sqrt{s}= 13$ TeV compared to theoretical predictions. The cross section is parametrized using a Levy-Tsallis function (dashed grey line), where the fit parameters are given in Table 2. The systematic uncertainty of the measurement is denoted by boxes, excluding the normalization uncertainty of 2.2%, which is shown separately as a grey box in the bottom panel of the figure. To account for the finite width of each $p_{\rm T}$-interval, the data points are shifted according to the underlying spectrum, as described by the fit. The red line represents the theoretical prediction obtained using the PYTHIA8.2 event generator with the Monash 2013 tune . The width of the line indicates the statistical uncertainty of the prediction. The blue dashed line shows a NLO calculation incorporating $\omega$ fragmentation based on a broken SU(3) model, where all scales are chosen to be $\mu = p_{\rm T}$ and the blue shaded band denotes the scale uncertainty The bottom panel shows the ratio of the data, as well as the theoretical predictions to the Levy-Tsallis parametrization. |  |
Figure 5
Ratio of $\omega/\pi^0$ production as a function of transverse momentum for pp collisions at $\sqrt{s} = 13$ TeV. The data is compared to various measurements at lower collision energies ranging from $\sqrt{s}=62$ to 7 TeV. The data is confronted with various theoretical calculations, which are given in the legend and described in the text. In addition, the ratio obtained from \mt-scaling of the measured $\pi^0$ meson cross section is shown. |  |