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.
Raw primary antihelium3-to-helium3 ratio as a function of the momentum p_primary.
Raw primary antihelium3-to-helium3 ratio from Geant4-based MC simulations as a function of the momentum p_primary with default sigma_inel(3Hebar).
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.
Two-particle azimuthal correlations are measured with the ALICE apparatus in pp collisions at $\sqrt{s} = 13$ TeV to explore strangeness- and multiplicity-related effects in the fragmentation of jets and the transition regime between bulk and hard production, probed with the condition that a strange meson (K$^{0}_{\rm S}$) or baryon ($\Lambda$) with transverse momentum $p_{\rm T} > 3$ GeV/c is produced. Azimuthal correlations between kaons or $\Lambda$ hyperons with other hadrons are presented at midrapidity for a broad range of the trigger ($3 < p_{\rm T}^{\rm trigg} < 20$ GeV/$c$) and associated particle $p_{\rm T}$ (1 GeV/$c$$< p_{\rm T}^{\rm assoc} < p_{\rm T}^{\rm trigg}$), for minimum-bias events and as a function of the event multiplicity. The near- and away-side peak yields are compared for the case of either K$^{0}_{\rm S}$ or $\Lambda$($\overline{\Lambda}$) being the trigger particle with that of inclusive hadrons (a sample dominated by pions). In addition, the measurements are compared with predictions from PYTHIA 8 and EPOS LHC event generators.
Two-dimensional $K_S^0$-h correlation function with $3<p_{\mathrm{T}}^{\mathrm{trigg}}< 4 \mathrm{GeV}/c$ and $1 \mathrm{GeV}/c<p_{\mathrm{T}}^{\mathrm{assoc}}< p_{\mathrm{T}}^{\mathrm{trigg}} $
Two-dimensional $K_S^0$-h correlation function with $3<p_{\mathrm{T}}^{\mathrm{trigg}}< 4 \mathrm{GeV}/c$ and $1 \mathrm{GeV}/c<p_{\mathrm{T}}^{\mathrm{assoc}}< p_{\mathrm{T}}^{\mathrm{trigg}} $
$\Delta\varphi$ projection of h-h correlation function with $3<p_{\mathrm{T}}^{\mathrm{trigg}}< 4 \mathrm{GeV}/c$ and $1 \mathrm{GeV}/c<p_{\mathrm{T}}^{\mathrm{assoc}}< p_{\mathrm{T}}^{\mathrm{trigg}} $
The average total energy as well as its hadronic and electromagnetic components are measured with the CMS detector at pseudorapidities $-$6.6 $<\eta<-$5.2 in proton-proton collisions at a centre-of-mass energy $\sqrt{s}=$ 13 TeV. The results are presented as a function of the charged particle multiplicity in the region $|\eta|< $2. This measurement is sensitive to correlations induced by the underlying event structure over a very wide pseudorapidity region. The predictions of Monte Carlo event generators commonly used in collider experiments and ultra-high energy cosmic ray physics are compared to the data.
Average total energy reconstructed in the region −6.6 < eta < −5.2 as a function of the number of reconstructed tracks for abs(eta)<2.
Average total energiy reconstructed in the region −6.6 < eta < −5.2 normalised to that in the first bin (Nch< 10) as a function of the number of reconstructed tracks for abs(eta)<2.
Average electromagnetic energy reconstructed in the region −6.6 < eta < −5.2 as a function of the number of reconstructed tracks for abs(eta)<2.
The cross-section for inelastic proton-proton collisions at a centre-of-mass energy of 13\,TeV is measured with the LHCb detector. The fiducial cross-section for inelastic interactions producing at least one prompt long-lived charged particle with momentum $p>2$\,GeV/$c$ in the pseudorapidity range $2<\eta<5$ is determined to be $\sigma_{\rm acc}= 62.2 \pm 0.2 \pm 2.5$\,mb. The first uncertainty is the intrinsic systematic uncertainty of the measurement, the second is due to the uncertainty on the integrated luminosity. The statistical uncertainty is negligible. Extrapolation to full phase space yields the total inelastic proton-proton cross-section $\sigma_{\rm inel}= 75.4 \pm 3.0 \pm 4.5$\,mb, where the first uncertainty is experimental and the second due to the extrapolation. An updated value of the inelastic cross-section at a centre-of-mass energy of 7\,TeV is also reported.
The cross-section for inelastic $pp$ collisions at a centre-of-mass energy $\sqrt{s} = 13$ TeV, yielding one or more prompt long-lived charged particles in the kinematic range $p > 2.0$ GeV/$c$ and $2.0 < \eta < 5.0$ (LHCb acceptance). The quoted uncertainty that is almost completely systematic in nature as the purely statistical uncertainty is found negligible. A particle is long-lived if its proper (mean) lifetime is larger than 30 ps, and it is prompt if it is produced directly in the $pp$ interaction or if none of its ancestors is long-lived.
The total cross-section for inelastic $pp$ collisions at a centre-of-mass energy $\sqrt{s} = 13$ TeV, extrapolated from Monte Carlo in similar way to measurement at $\sqrt{s}=7$ TeV.
Update of the total cross-section for inelastic $pp$ collisions at a centre-of-mass energy $\sqrt{s} = 7$ TeV due to improved calibration of the luminosity scale.
The cross-section for inelastic proton-proton collisions, with at least one prompt long-lived charged particle of transverse momentum $p_{\rm T}>0.2$ GeV/$c$ in the pseudorapidity range $2.0<\eta<4.5$, is measured by the LHCb experiment at a centre-of-mass energy of $\sqrt{s}=7$ TeV. The cross-section in this kinematic range is determined to be $\sigma_{\rm inel}^{\rm acc} = 55.0 \pm 2.4$ mb within the spectrometer acceptance with an experimental uncertainty that is dominated by systematic contributions. Extrapolation to the full phase space, using PYTHIA 6, yields $\sigma_{\rm inel} = 66.9 \pm 2.9 \pm 4.4$ mb, where the first uncertainty is experimental and the second is due to the extrapolation.
The cross-section for inelastic $pp$ collisions at a centre-of-mass energy $\sqrt{s} = 7$ TeV, yielding one or more prompt long-lived charged particles in the kinematic range $p_T > 0.2$ GeV/$c$ and $2.0 < \eta < 4.5$ (LHCb acceptance). The quoted uncertainty that is almost completely systematic in nature as the purely statistical uncertainty is two orders of magnitude smaller.
The total cross-section for inelastic $pp$ collisions at a centre-of-mass energy $\sqrt{s} = 7$ TeV, extrapolated using PYTHIA6 and different soft QCD tunes provided by PYTHIA 8.201 to estimate its uncertainty.
The energy flow created in pp collisions at is studied within the pseudorapidity range 1.9<η<4.9 with data collected by the LHCb experiment. The measurements are performed for inclusive minimum-bias interactions, hard scattering processes and events with an enhanced or suppressed diffractive contribution. The results are compared to predictions given by Pythia-based and cosmic-ray event generators, which provide different models of soft hadronic interactions.
Charged energy flow for inclusive mininum bias events, requiring at least one charged particle in the pseudorapidity range 1.9 < eta < 4.9.
Charged energy flow for hard scattering events, requiring at least one charged particle with transverse momentum > 3 GeV and in the pseudorapidity range 1.9 < eta < 4.9.
Charged energy flow for diffractive enriched events, requiring no charged particles in the pseudorapidity range -3.5 < eta < -1.5 and at least one charged particle in the pseudorapidity range 1.9 < eta < 4.9.
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