First measurement of the absorption of $^{3}\overline{\rm He}$ nuclei in matter and impact on their propagation in the galaxy

The collaboration
Nature Phys. 19 (2023) 61-71, 2023.

Abstract
In our Galaxy, light antinuclei composed of antiprotons and antineutrons can be produced through high-energy cosmic-ray collisions with the interstellar medium or could also originate from the annihilation of dark-matter particles that have not yet been discovered. On Earth, the only way to produce and study antinuclei with high precision is to create them at high-energy particle accelerators. Although the properties of elementary antiparticles have been studied in detail, the knowledge of the interaction of light antinuclei with matter is limited. We determine the disappearance probability of $^{3}\overline{\rm He}$ when it encounters matter particles and annihilates or disintegrates within the ALICE detector at the Large Hadron Collider. We extract the inelastic interaction cross section, which is then used as input to calculations of the transparency of our Galaxy to the propagation of $^{3}\overline{\rm He}$ stemming from dark-matter annihilation and cosmic-ray interactions within the interstellar medium. For a specific dark-matter profile, we estimate a transparency of about 50%, whereas it varies with increasing $^{3}\overline{\rm He}$ momentum from 25% to 90% for cosmic-ray sources. The results indicate that $^{3}\overline{\rm He}$ nuclei can travel long distances in the Galaxy, and can be used to study cosmic-ray interactions and dark-matter annihilation.

• #### Table 1

Figure 1(c)

10.17182/hepdata.133480.v1/t1

Raw primary antihelium3-to-helium3 ratio as a function of the momentum p_primary.

• #### Table 2

Figure 1(c)

10.17182/hepdata.133480.v1/t2

Raw primary antihelium3-to-helium3 ratio from Geant4-based MC simulations as a function of the momentum p_primary with default sigma_inel(3Hebar).

• #### Table 3

Figure 1(c)

10.17182/hepdata.133480.v1/t3

Raw primary antihelium3-to-helium3 ratio from Geant4-based MC simulations as a function of the momentum p_primary with sigma_inel(3Hebar)x0.5.

• #### Table 4

Figure 1(c)

10.17182/hepdata.133480.v1/t4

Raw primary antihelium3-to-helium3 ratio from Geant4-based MC simulations as a function of the momentum p_primary with sigma_inel(3Hebar)x1.5.

• #### Table 5

Figure 1(d)

10.17182/hepdata.133480.v1/t5

Raw primary antihelium3-to-helium3 ratio as a function of the momentum p_primary.

• #### Table 6

Figure 1(d)

10.17182/hepdata.133480.v1/t6

Raw primary antihelium3-to-helium3 ratio from Geant4-based MC simulations as a function of the momentum p_primary with default sigma_inel(3Hebar).

• #### Table 7

Figure 1(d)

10.17182/hepdata.133480.v1/t7

Raw primary antihelium3-to-helium3 ratio from Geant4-based MC simulations as a function of the momentum p_primary with sigma_inel(3Hebar)x0.5.

• #### Table 8

Figure 1(d)

10.17182/hepdata.133480.v1/t8

Raw primary antihelium3-to-helium3 ratio from Geant4-based MC simulations as a function of the momentum p_primary with sigma_inel(3Hebar)x1.5.

• #### Table 9

Figure 2(left)

10.17182/hepdata.133480.v1/t9

Inelastic interaction cross section of antihelium-3 on an averaged material element of the ALICE detector (ITS+TPC analysis).

• #### Table 10

Figure 2(left)

10.17182/hepdata.133480.v1/t10

Inelastic interaction cross section of antihelium-3 on an averaged material element of the ALICE detector (ITS+TPC+TOF analysis).

• #### Table 11

Figure 2(right)

10.17182/hepdata.133480.v1/t11

Inelastic interaction cross section of antihelium-3 on an averaged material element of the ALICE detector (ITS+TPC+TOF analysis).

• #### Table 12

Figure 4(left)

10.17182/hepdata.133480.v1/t12

Antihelium-3 cosmic-ray flux from background before the solar modulation

• #### Table 13

Figure 4(left)

10.17182/hepdata.133480.v1/t13

Antihelium-3 cosmic-ray flux from dark matter before the solar modulation

• #### Table 14

Figure 4(left)

10.17182/hepdata.133480.v1/t14

Transparency of the galaxy to antihelium-3 nuclei from background before the solar modulation

• #### Table 15

Figure 4(left)

10.17182/hepdata.133480.v1/t15

Transparency of the galaxy to antihelium-3 nuclei from dark matter before the solar modulation

• #### Table 16

Figure 4(right)

10.17182/hepdata.133480.v1/t16

Antihelium-3 cosmic-ray flux from background after the solar modulation

• #### Table 17

Figure 4(right)

10.17182/hepdata.133480.v1/t17

Antihelium-3 cosmic-ray flux from dark matter after the solar modulation

• #### Table 18

Figure 4(right)

10.17182/hepdata.133480.v1/t18

Transparency of the galaxy to antihelium-3 nuclei from background after the solar modulation

• #### Table 19

Figure 4(right)

10.17182/hepdata.133480.v1/t19

Transparency of the galaxy to antihelium-3 nuclei from dark matter after the solar modulation

• #### Table 20

Figure 1 Extended Data (left)

10.17182/hepdata.133480.v1/t20

Inelastic interaction cross section of antihelium-3 on proton from the fit to the ALICE data.

• #### Table 21

Figure 1 Extended Data (right)

10.17182/hepdata.133480.v1/t21

Inelastic interaction cross section of antihelium-3 on helium-4 from the fit to the ALICE data.