Observation of ${\pi }^{-}{K}^{+}$ and ${\pi }^{+}{K}^{-}$ atoms

Abstract

The observation of hydrogen-like $\pi K$ atoms, consisting of ${\pi }^{-}{K}^{+}$ or ${\pi }^{+}{K}^{-}$ mesons, is presented. The atoms have been produced by 24 GeV/$c$ protons from the CERN PS accelerator, interacting with platinum or nickel foil targets. The breakup (ionisation) of $\pi K$ atoms in the same targets yields characteristic $\pi K$ pairs, called "atomic pairs", with small relative momenta in the pair centre-of-mass system. The upgraded DIRAC experiment has observed $349\pm 62$ such atomic $\pi K$ pairs, corresponding to a signal of 5.6 standard deviations.

13 pages, 7 figures

References in corpus (2)

• First $\pi K$ atom lifetime and $\pi K$ scattering length measurements
• Direct calculation of the probability of pionium ionization in the target

Cited by in corpus (7)

• Antinuclei in Heavy-Ion Collisions
• Determination of $s$- and $p$-wave $I=1/2$ $K\pi$ scattering amplitudes in $N_{\mathrm{f}}=2+1$ lattice QCD
• Measurement of the $\pi K$ atom lifetime and the $\pi K$ scattering length
• The MC-QTAIM: A framework for extending the atoms in molecules analysis beyond purely electronic systems
• First measurement of a long-lived ${\pi }^{+}{\pi }^{-}$ atom lifetime
• Manifestation of kaonium in the $e^{+}{e}^{-}\to K^{+}{K}^{-}$ process
• Investigation of $K^{+}{K}^{-}$ pairs in the effective mass region near $2m_K$