The Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany, provides unique possibilities for a new generation of hadron-, nuclear- and atomic physics experiments. The future antiProton ANnihilations at DArmstadt (PANDA or $$\overline{\mathrm{P}}$$ P ¯ ANDA) experiment at FAIR will offer a broad physics programme, covering different aspects of the strong interaction. Understanding the latter in the non-perturbative regime remains one of the greatest challenges in contemporary physics. The antiproton–nucleon interaction studied with PANDA provides crucial tests in this area. Furthermore, the high-intensity, low-energy domain of PANDA allows for searches for physics beyond the Standard Model, e.g. through high precision symmetry tests. This paper takes into account a staged approach for the detector setup and for the delivered luminosity from the accelerator. The available detector setup at the time of the delivery of the first antiproton beams in the HESR storage ring is referred to as the Phase One setup. The physics programme that is achievable during Phase One is outlined in this paper.

This paper reports on Monte Carlo simulation results for future measurements of the moduli of time-like proton electromagnetic form factors, $$|G_{E}|$$ | G E | and $$|G_{M}|$$ | G M | , using the $$\bar{p} p \rightarrow \mu ^{+} \mu ^{-}$$ p ¯ p → μ + μ - reaction at $$\overline{\text {P}}\text {ANDA}$$ P ¯ ANDA (FAIR). The electromagnetic form factors are fundamental quantities parameterizing the electric and magnetic structure of hadrons. This work estimates the statistical and total accuracy with which the form factors can be measured at $$\overline{\text {P}}\text {ANDA}$$ P ¯ ANDA , using an analysis of simulated data within the PandaRoot software framework. The most crucial background channel is $$\bar{p} p \rightarrow \pi ^{+} \pi ^{-}$$ p ¯ p → π + π - , due to the very similar behavior of muons and pions in the detector. The suppression factors are evaluated for this and all other relevant background channels at different values of antiproton beam momentum. The signal/background separation is based on a multivariate analysis, using the Boosted Decision Trees method. An expected background subtraction is included in this study, based on realistic angular distributions of the background contribution. Systematic uncertainties are considered and the relative total uncertainties of the form factor measurements are presented.

In the interstellar medium at rest, containing low-frequency magnetohydrodynamic linearly polarized slab Alfvén waves, the anisotropy of relativistic galactic cosmic rays consists of two parts: the streaming anisotropy g s (z, p,μ), caused by the spatial gradient of the isotropic part of the cosmic ray distribution function, and the interstellar Compton–Getting anisotropy , caused by the momentum gradient of the isotropic part of the cosmic ray distribution function. Both anisotropies depend differently on the cosmic ray pitch-angle cosine μ, cosmic ray momentum p, and cross-helicity state H c of the Alfvenic slab turbulence. First, the streaming anisotropy is independent from H c and varies as with η = 2 − s, where s denotes the power-law spectral index of interstellar turbulence. Second, the interstellar Compton–Getting anisotropy is independent of momentum and linearly proportional to . These different pitch-angle dependencies can be tested by the Liouville mapping technique to infer the pristine interstellar cosmic ray anisotropy from measurements inside the solar system. For cosmic rays with energy of 4 TeV the derived pristine interstellar cosmic ray anisotropy suggest the linear ( ) pitch-angle dependence. This is well explained by the interstellar Compton–Getting anisotropy, provided the Alfvén speed in the local interstellar medium is about 62 km s−1.

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The analytical theory of diffusive acceleration of cosmic rays at parallel stationary shock waves of arbitrary speed with magnetostatic turbulence is developed from first principles. The theory is based on the diffusion approximation to the gyrotropic cosmic-ray particle phase-space distribution functions in the respective rest frames of the up- and downstream medium. We derive the correct cosmic-ray jump conditions for the cosmic-ray current and density, and match the up- and downstream distribution functions at the position of the shock. It is essential to account for the different particle momentum coordinates in the up- and downstream media. Analytical expressions for the momentum spectra of shock-accelerated cosmic rays are calculated. These are valid for arbitrary shock speeds including relativistic shocks. The correctly taken limit for nonrelativistic shock speeds leads to a universal broken power-law momentum spectrum of accelerated particles with velocities well above the injection velocity threshold, where the universal power-law spectral index is independent of the flow compression ratio r. For nonrelativistic shock speeds, we calculate for the first time the injection velocity threshold, settling the long-standing injection problem for nonrelativistic shock acceleration.