Narrow Results

This paper gives an introduction to the hadron physics program and the planned PANDA experiment at the future FAIR facility located at GSI in Germany.

We studied the total variation of e⁺ and spectra due to the parameters uncertainties of propagation models and cross sections. We used B/C data and Galprop code and we derived also the uncertainty bands for subFe/Fe ratio, H and He. Finally we have considered a neutralino induced component in the mSUGRA framework and we have concluded that even for the model with diffusion and convection, where secondary spectra gives a good fit of the data, neutralino induced contribution can not be excluded up to now due to the overall uncertainties.

The L3+C measurement of the momentum spectrum of atmospheric muons between 20 and 3000 GeV for zenith angles ranging from 0° to 58° is presented and compared to theoretical predictions. An upper flux limit on the antiproton to proton ratio using the moon shadow is reported and an overview on the ongoing L3+C data analysis is given.

Fundamental questions concerning the strong interaction are addressed by the PANDA experiment at the future FAIR facility at GSI-Darmstadt. PANDA will be a general purpose detector of modular design optimized to measure the interaction of an antiproton beam with proton and heavy nuclear targets. The physics program at PANDA covers a wide range of topics including gluonic excitations, spectroscopy of strange and charm mesons, Drell-Yan and CP violating processes. This contribution focuses on the part of the physics program dealing with antiproton - proton annihilation.

PANDA is a future antiproton experiment designed to study fundamental questions of hadron and nuclear physics. It will work as a fixed-target facility, hence – due to the Lorentz boost – the distribution of reaction products will be strongly forward-peaked, in particular for the near-threshold measurements. Thus, the Forward Spectrometer, covering the most forward angles (θ_lab < 10°) is one of the key components of PANDA.

In this contribution, current design of the Forward Spectrometer is presented. Spectrometer components, including dipole magnet, tracking detectors, electromagnetic and hadron calorimeter, muon counters, RICH detector and TOF system are discussed. Results of simulations are shown along with tests of the prototype detectors performed in a high-rate environment.

A schematic Monte Carlo simulation is used to examine the potential of exclusive hyperon-antihyperon pair production close to threshold in antiproton nucleus interactions to extract information on the interaction of antihyperons in nuclei. It is demonstrated that for pairs produced at antiproton momenta of 1.66 GeV/c the asymmetry is sufficiently sensitive even if the density as well as the momentum dependencies of the potentials are considered. Data taken earlier by the PS185 Collaboration prove that these measurements are feasible.

A beam channel of polarized protons and antiprotons produced from decays of $\mathrm{\Lambda }$- and anti-$\mathrm{\Lambda }$-hyperons for the SPASCHARM experiment is to be built at IHEP U-70 accelerator in Protvino, Russia. The methods for tagging and measuring polarization of the beam (anti)protons are discussed in this report. The fast on-line beam tagging exploits the correlations between polarization and kinematics of (anti)protons originated from (anti)$\mathrm{\Lambda }$-decays. In the intermediate focus of primary target, decay (anti)protons of different transverse polarizations are spatially dispersed transversely with respect to the beam axis. The tagging system, consisting of fast beam detectors with good spatial resolution, measures the momentum and trajectory of each beam particle, including its position at the intermediate focus, thus allowing instant (on-line) assignment of the transverse polarization value to each (anti)proton. This system is also extremely useful for the beam channel tuning. While being fast and convenient, the polarization tagging fully relies on computing of particle transportation in the beam channel. In order to verify the real beam polarization and operating of the tagging system and beam channel, the independent absolute beam polarimetry is to be used. It is based on measuring the spin asymmetries in elastic scattering of beam (anti)protons in Coulomb-Nuclear Interference (CNI) and diffractive kinematic regions. It is estimated that less than one week of data taking would allow measuring an absolute beam polarization at the statistical accuracy of $\sim$4–5%.

We address the commissioning of the experimental equipment and the machine studies required for the first spin-filtering experiment with protons at the COSY ring in Jülich (Germany) at a beam kinetic energy of 49.3 MeV. The implementation of a low-beta insertion made it possible to achieve beam lifetimes of 8000 s in the presence of a dense polarized hydrogen storage cell target. The developed techniques can be directly applied to antiproton machines and allow for the determination of the spin-dependent pbar-p cross sections via spin-filtering.

A new experiment SPASCHARM for systematic study of polarization phenomena in the inclusive and exclusive hadronic reactions in the energy range of IHEP accelerator U-70 (12–50GeV) is currently under development. The universal experimental setup will detect dozens of various resonances and stable particles produced in collisions of unpolarized beams with the polarized target, and at the next stage, using polarized proton and antiproton beams. At the beginning, the final states consisting of light quarks ($u$, $d$, $s$) will be reconstructed, and later on the charmonium states will be studied. Measurements are planned for a variety of beams: ${\pi }^{\pm },K^{\pm },p$, antiprotons. Hyperon polarization and spin density matrix elements of the vector mesons will be measured along with the single-spin asymmetry (SSA). The 2$\pi$-acceptance in azimuth, which is extremely useful for reduction of systematic errors in measurements of spin observables, will be implemented in the experiment. The solid angle acceptance of the setup, $\mathrm{\Delta }\theta \approx 250$ mrad vertically and 350 mrad horizontally in the beam fragmentation region, covers a wide range of kinematic variables $p_T$ and $x_F$. This provides the opportunity for separating dependences on these two variables which is usually not possible in the setups with a small solid angle acceptance. Unlike some previous polarization experiments, the SPASCHARM will be able to simultaneously accumulate and record data on the both, charged and neutral particle production.

A schematic Monte Carlo simulation is used to examine the potential of exclusive hyperon-antihyperon pair production close to threshold in antiproton nucleus interactions to extract information on the interaction of antihyperons in nuclei. It is demonstrated that for pairs produced at antiproton momenta of 1.66 GeV/c the asymmetry is sufficiently sensitive even if the density as well as the momentum dependencies of the potentials are considered. Data taken earlier by the PS185 Collaboration prove that these measurements are feasible.

The effect of the dissociator cooling temperature has been tested in order to explain the unexpected RHIC atomic beam intensity. Studies on trumpet nozzle geometry, compared to standard sonic nozzle have been performed, both with simulation methods and test bench measurements on molecular beams, obtaining promising results.

We discuss polarizing a proton beam in a storage ring, either by selective removal or by spin-flip of the stored ions. Prompted by recent, conflicting calculations, we have carried out a measurement of the spin-flip cross section in low-energy electron-proton scattering. The experiment uses the cooling electron beam at COSY as an electron target. A re-analysis of the data leeds to reduced statistical errors, resulting in reduction by a factor of four of the upper limit for the spin-flip cross section. The measured cross sections are too small for making spin-flip a viable tool in polarizing a stored beam.