CERN Accelerating science

(Color online) $m^2/z^2$ distribution for ${}^{4}\overline{{\rm He}}$ candidates (green). The background (magenta) is constructed by selecting all candidates outside the \antihe TPC window of 3\,$\sigma$ around the alpha mass hypothesis ($|n\sigma_{\rm TPC}({}^{4}\overline{{\rm He}})| > 3$) and in addition outside the 3\,$\sigma$ window around the deuteron mass hypothesis ($|n\sigma_{\rm TPC}(\overline{{\rm d}})| > 3$). The blue line is an exponential fit to the rise at lower masses originating from ${}^{3}\overline{{\rm He}}$ candidates.

Measured transverse-momentum distributions of ${}^{4}$He and ${}^{4}\overline{{\rm He}}$ (upper panel). The vertical lines indicate the statistical uncertainties, while the boxes represent the systematic ones. In the case that the statistical uncertainties would overlap the ${}^{4}$He points are a bit shifted on the x-axis. The lower panel shows the ratio between ${}^{4}\overline{{\rm He}}$ and ${}^{4}$He with statistical and uncorrelated systematic uncertainties as the correlated systematic uncertainties cancel.

(Color online) Combined blast-wave fit of all available light flavored hadron $p_{\rm T}$ spectra including nuclei~\cite{ALICE:2019hno,Nuclei_5TeV} (left) and only p, $\overline{\mathrm{d}}$, $\overline{\mathrm{t}}$, ${}^{3}\overline{\mathrm{He}}$ and ${}^{4}$He $p_{\rm T}$ spectra (right) in Pb--Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV for 0--10\% central events (upper panels). The lower panels show the ratio between each data point and the blast-wave model fit for each species.

(Color online) Combined blast-wave fit of all available light flavored hadron $p_{\rm T}$ spectra including nuclei~\cite{ALICE:2019hno,Nuclei_5TeV} (left) and only p, $\overline{\mathrm{d}}$, $\overline{\mathrm{t}}$, ${}^{3}\overline{\mathrm{He}}$ and ${}^{4}$He $p_{\rm T}$ spectra (right) in Pb--Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV for 0--10\% central events (upper panels). The lower panels show the ratio between each data point and the blast-wave model fit for each species.

(Color online) The coalescence parameter $B_4$ as a function of $p_{\rm T}/A$, calculated from the averaged ${}^{4}$He and \antihe spectra and the protons from~\cite{ALICE:2019hno}. Statistical uncertainties are indicated by the vertical lines and the boxes correspond to the systematic uncertainties. The blue dashed line and the full black line indicate the values for the SHM combined with blast-wave \pt shapes and the coalescence predictions from Refs.~\cite{Bellini:2018epz,Bellini:2019zqc}, respectively.

(Color online) $^4$He/p ratios for the measured data points as a function of charged-particle multiplicity $\langle {\rm d}N_{\rm ch}/{\rm d}\eta \rangle_{|\eta_{\rm lab}|<0.5}$ compared to model predictions. For comparison the result from the 10\% most central Pb--Pb collisions at $\sqrt{s_\mathrm{NN}} = 2.76$ TeV~\cite{Acharya:2017bso} and the upper limit at 90\% CL from p--Pb collisions at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV~\cite{Acharya:2019xmu} is also shown. The thermal model curves are from the CSM~\cite{Vovchenko:2018fiy}. For the coalescence model two different approaches are displayed: analytical and UrQMD hybrid coalescence~\cite{jan,kjs}. The analytical coalescence is shown for five different substructures and the thickness of the bands reflects the uncertainties of the calculation. For the UrQMD model the band is representing the statistical uncertainty of the prediction.