The study of the production of nuclei and antinuclei in pp collisions has proven to be a powerful tool to investigate the formation mechanism of loosely bound states in high-energy hadronic collisions. In this paper, the production of protons, deuterons and $^3$He and their charge conjugates at midrapidity is studied as a function of the charged-particle multiplicity in inelastic pp collisions at $\sqrt{s}=5.02$ TeV using the ALICE detector. Within the uncertainties, the yields of nuclei in pp collisions at $\sqrt{s}=5.02$ TeV are compatible with those in pp collisions at different energies and to those in p-Pb collisions when compared at similar multiplicities. The measurements are compared with the expectations of coalescence and Statistical Hadronisation Models. The results suggest a common formation mechanism behind the production of light nuclei in hadronic interactions and confirm that they do not depend on the collision energy but on the number of produced particles.
Eur. Phys. J. C 82, 289 (2022)
HEP Data
e-Print: arXiv:2112.00610 | PDF | inSPIRE
CERN-EP-2021-250
Figure group
Figure 1
Transverse-momentum spectra of (anti)protons (left), (anti)deuterons (center) and (anti)helions (right) in the different multiplicity classes, reported in Table \ref{tab:yields}. (Anti)deuteron and (anti)proton spectra are fitted with a L\'evy-Tsallis function , while (anti)helion spectra are fitted with an exponential function with respect to the transverse mass \mt. |  |
Figure 2
Mean transverse momentum of (anti)protons (left), (anti)deuterons (centre) and (anti)helions (right) in pp collisions at $\sqrt{s} = 5.02$ TeV, in high-multiplicity pp collisions at $\sqrt{s} = 13$ TeV , in INEL $>$ 0 pp collisions at $\sqrt{s} = 13$ TeV and at $\sqrt{s} = 7$ TeV , and in p--Pb collisions at $\snn = 5.02$ TeV . The statistical uncertainties are represented by vertical bars while the systematic uncertainties are represented by boxes. |  |
Figure 3
Coalescence parameters $B_2$ for (anti)deuterons (left) and $B_3$ for (anti)helions (right) for different multiplicity classes. The multiplicity decreases moving from the bottom up. The statistical uncertainties are represented by vertical bars while the systematic uncertainties are represented by boxes. $B_{\mathrm{A}}$ is shown as a function of $\pt/A$, being $A = 2$ the mass number of deuteron and $A = 3$ the mass number of helion. |  |
Figure 4
Left: $B_2$ as a function of multiplicity in INEL $>$ 0 pp collisions at $\sqrt{s} = 5.02$ TeV, in high-multiplicity pp collisions at $\sqrt{s} = 13$ TeV , in INEL $>$ 0 pp collisions at $\sqrt{s} = 13$ TeV and at $\sqrt{s} = 7$ TeV , and in p--Pb collisions at $\snn = 5.02$ TeV . Right: $B_3$ as a function of multiplicity in INEL $>$ 0 pp collisions at $\sqrt{s} = 5.02$ TeV, in high-multiplicity pp collisions at $\sqrt{s} = 13$ TeV , in INEL $>$ 0 pp collisions at $\sqrt{s} = 13$ TeV and at $\sqrt{s} = 7$ TeV , and in p--Pb collisions at $\snn = 5.02$ TeV . The statistical uncertainties are represented by vertical bars while the systematic uncertainties are represented by boxes. The two lines are theoretical predictions of the coalescence model based on two different parameterisations of the system radius as a function of multiplicity. |  |
Figure 5
Ratio between the \pt-integrated yields of nuclei and protons as a function of multiplicity for (anti)deuterons (left) and (anti)helions (right). Measurements are performed in INEL $>$ 0 pp collisions at $\sqrt{s} = 5.02$ TeV, in high-multiplicity pp collisions at $\sqrt{s} = 13$ TeV , in INEL $>$ 0 pp collisions at $\sqrt{s} = 13$ TeV and at $\sqrt{s} = 7$ TeV , and in p--Pb collisions at $\snn = 5.02$ TeV . The statistical uncertainties are represented by vertical bars while the systematic uncertainties are represented by boxes. The two black lines are the theoretical predictions of the Thermal-FIST statistical model for two sizes of the correlation volume $V_\mathrm{C}$. For (anti)deuterons, the green band represents the expectation from a coalescence model . For (anti)helion, the green and blue lines represent the expectations from a two-body and three-body coalescence models |  |