Exclusive meson production at HERMES

The data were accumulated with the HERMES forward spectrometer using the 27.6 GeV longitudinally polarized electron or positron beam of HERA. Exclusive electroproduction of $\omega$ mesons on unpolarized hydrogen and deuterium targets is studied in the kinematic region of $Q^2>1.0$ GeV$^2$, 3.0 GeV $< W <$ 6.3 GeV, and $-t'< 0.2$ GeV$^{2}$, while for $\rho^0$-meson production on a transversely polarized hydrogen target $-t'< 0.4$ GeV$^{2}$ is used. Spin-density matrix elements for $\omega$ production are presented in projections of $Q^2$ or $-t'$, while the ratios of the helicity amplitudes for the reaction $\gamma^*+p \to \rho^0+p$ are obtained in the entire kinematic region. The usage of the transversely polarized target allows for the first time the extraction of the ratios of certain nucleon-helicity-flip amplitudes to the natural-parity exchange amplitude $T_{0\frac{1}{2}0\frac{1}{2}}$ without the nucleon-helicity flip describing the longitudinal $\rho^0$-meson production by the longitudinal virtual photon. Violation of $s$-channel helicity conservation is observed for both mesons. A dominant contribution from unnatural-parity exchange (UPE) is established for special combinations of the $\omega$ spin-density matrix elements. For $\rho^0$-meson production, the UPE amplitude without the nucleon-helicity flip, $U_{1\frac{1}{2}1\frac{1}{2}}$, is shown to be the largest UPE amplitude. Good agreement is found between the HERMES data on $\omega$ production on the proton and results of the perturbative QCD-inspired Goloskokov-Kroll model that includes pion-pole contribution.Comment: 6 pages, 4 figures, XXIV International Workshop on Deep-Inelastic Scattering and Related Subjects, DESY Hamburg, Germany, 11-15 April, 201

Extraction of Helicity Amplitude Ratios from Exclusive ρ0\rho^0-meson Electroproductionon Transversely Polarized Proton

Exclusive $\rho^0$-meson electroproduction is studied by the HERMES experiment, using the 27.6 GeV longitudinally polarized electron/positron beam of HERA and a transversely polarized hydrogen target, in the kinematic region 1.0 GeV$^2$ < Q$^2$ < 7.0 GeV$^2$, 3.0 GeV < W < 6.3 GeV, and -t' < 0.4 GeV$^2$. Using an unbinned maximum-likelihood method, 25 parameters are extracted. They determine the real and imaginary parts of the ratios of certain helicity amplitudes (describing$\rho^0$-meson production by a virtual photon) and the dominant amplitude $F_{0,\frac{1}{2},0,\frac{1}{2}}$ without the nucleon-helicity flip. The latter amplitude describes the production of a longitudinal $\rho^0$ meson by a longitudinal virtual photon. The transverse target polarization allows for the first time the extraction of ratios of a number of nucleon-helicity-flip amplitudes to $F_{0,\frac{1}{2},0,\frac{1}{2}}$. The ratios of nucleon-helicity-non-flip amplitudes to $F_{0,\frac{1}{2},0,\frac{1}{2}}$ are found to be in good agreement with those from the previous HERMES analysis. A comparison of the extracted amplitude ratios with the Goloskokov-Kroll model shows the necessity to add pion exchange amplitudes with positive $\pi\rho$ form factor to the amplitudes based on generalized parton distributions to improve the HERMES data description

Reduction of soil layer losses when harvesting sugar beet in the conditions of the central black earth region

When cultivating sugar beets, harvesting is one of the most labor-intensive operations. But in terms of quality and operational and technological performance, the machines used do not meet modern agrotechnical requirements, especially in conditions of high soil moisture (25 - 29%). With an increase in soil moisture, its adhesion to the working surfaces of the digging organs and the heap cleaner increases, reducing their separating ability. We propose to improve the cleaning technology by modernizing the design of the separating stars. This is achieved by using cylindrical brushes (in the amount of three pieces), which are mounted vertically to the horizontal plane of the star's rods. One end of the cylindrical brush is attached to one of the ends of the star bar, and the other end of the brushes is in the hollow bracket. All brushes are located at the same distance from each other along the periphery of the star. The second ends of the brushes, located in the hollow bracket, are fixed to each other and move freely in it. This improved design will allow the brushes to interact with the contaminated surface of the sprocket guard, improving their cleaning ability and eliminating cleaning breaks when working in harsh conditions

Beam-helicity asymmetries for single-hadron production in semi-inclusive deep-inelastic scattering from unpolarized hydrogen and deuterium targets

A measurement of beam-helicity asymmetries for single-hadron production in deep-inelastic scattering is presented. Data from the scattering of 27.6 GeV electrons and positrons off gaseous hydrogen and deuterium targets were collected by the HERMES experiment. The asymmetries are presented separately as a function of the Bjorken scaling variable, the hadron transverse momentum and the fractional energy for charged pions and kaons as well as for protons and anti-protons. These asymmetries are also presented as a function of the three aforementioned kinematic variables simultaneously

Hyperon signatures in the PANDA experiment at FAIR

We present a detailed simulation study of the signatures from the sequential decays of the triple-strange pbar p -> Ω+Ω- -> K+ΛbarK- Λ -> K+pbarπ+K-pπ- process in the PANDA central tracking system with focus on hit patterns and precise time measurement. We present a systematic approach for studying physics channels at the detector level and develop input criteria for tracking algorithms and trigger lines. Finally, we study the beam momentum dependence on the reconstruction efficiency for the PANDA detector