Speaker
Description
Precise knowledge of inclusive antiproton production cross sections is essential for interpreting high-precision cosmic-ray antiproton measurements (e.g. AMS-02) and for maximizing the sensitivity of indirect searches for dark matter. In the energy domain where most secondary antiprotons are produced in the Galaxy, interactions involving protons and helium dominate, yet accelerator data—especially for p–He at low center-of-mass energy—are sparse. As a consequence, nuclear-production uncertainties limit the accuracy of the antiproton source term used in propagation models.
AMBER (NA66) is a fixed-target experiment at the CERN SPS M2 beam line that is going to provide high-statistics measurements of antiproton production in p–He and p–p/d collisions. In 2023, AMBER carried out an extensive measurement with a proton beam incident on a liquid helium ($^{4}$He) target, covering an unprecedented beam-momentum range from 60 to 250 GeV/c ($\sqrt{s_{NN}}$=10.7–21.7 GeV). Event-by-event beam proton tagging is performed with two CEDAR Cherenkov detectors located about 40 m upstream of the target. Final-state hadrons are reconstructed in the two-stage magnetic spectrometer and identified with the RICH-1 detector.
We present the analysis strategy and preliminary antiproton yields and statistical uncertainties for p–He collisions at $\sqrt{s_{NN}}$=18.9 GeV, binned in laboratory momentum and transverse momentum, as a first step toward the double-differential production cross section $d^{2}\sigma/(dp dp_T$). Luminosity and target-related systematics are controlled via a data-driven determination of the target geometry and position from the reconstructed primary-vertex distribution, complemented by acceptance and efficiency corrections. We also outline the 2024 data set acquired with liquid hydrogen and deuterium targets at 80, 160 and 250 GeV/c, enabling a data-driven separation of p–p and p–n contributions and a stringent test of a possible isospin-driven antineutron/antiproton production asymmetries. With individual cross-section measurements at the ~5% level, AMBER is expected to substantially reduce the dominant nuclear-production uncertainties in cosmic-ray antiproton predictions.
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