Measurement of the low-energy antitriton inelastic cross section

In this Letter, the first measurement of the inelastic cross section for antitriton$-$nucleus interactions is reported, covering the momentum range of $0.8 \leq p <~ 2.4$ GeV/$c$. The measurement is carried out using data recorded with the ALICE detector in pp and Pb$-$Pb collisions at a centre-of-mass energy per nucleon of 13 TeV and 5.02 TeV, respectively. The detector material serves as an absorber for antitriton nuclei. The raw yield of (anti)triton nuclei measured with the ALICE apparatus is compared to the results from detailed ALICE simulations based on the GEANT4 toolkit for the propagation of (anti)particles through matter, allowing one to quantify the inelastic interaction probability in the detector material. This analysis complements the measurement of the inelastic cross section of antinuclei up to $A=3$ carried out by the ALICE Collaboration, and demonstrates the feasibility of the study of the isospin dependence of inelastic interaction cross section with the analysis techniques presented in this Letter.


Phys. Lett. B 848 (2024) 138337
HEP Data
e-Print: arXiv:2307.03603 | PDF | inSPIRE
Figure group

Figure 1

Left: raw primary $^3\overline{\rm H}/^3{\rm H}$ ratio as a function of the momentum $p_{\mathrm {primary}}$ in pp collisions at $\sqrt{s} = 13$ TeV. Right: ratio between the raw number of $^3\overline{\rm H}$ candidates reconstructed in the TOF and the raw number of $^3\overline{\rm H}$ reconstructed in the TPC in Pb$-$Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV as a function of the momentum $p_{\mathrm {primary}}$. In both panels, data are shown in black, the statistical and systematic uncertainties are shown as vertical bars and boxes, respectively. The results from ALICE MC simulations based on GEANT4 are shown as coloured bands, the different colours referring to the different inelastic cross sections implemented in the simulations, with default $\sigma_{\rm inel}$ described in Ref. [56]. The width of the MC band represents the statistical uncertainty of the simulation.

Figure 2

Left: inelastic interaction cross section for antitritons with the two analysis methods on an average material element of the ALICE detector as a function of the momentum $p$ at which the interaction occurs. Dashed black lines represent the default GEANT4 parameterisations for antitritons. Right: comparison between the results reported in the left panel and the results for $^3\overline{\rm He}$ inelastic cross section measured in Pb$-$Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV from Ref. [38]. Note that $^3\overline{\rm He}$ nuclei can be clearly identified in both TPC and TOF detectors over a much wider momentum range than $^3\overline{\rm H}$. In both panels, boxes show the statistical and systematic uncertainties summed in quadrature.