A. A. Kulbardis

Measurement of the spin rotation parameter A+ in the elastic scattering of positive pions on a longitudinally-polarized proton target in the second resonance region

Abstract The ITEP-PNPI collaboration presents the first results of the spin rotation parameter A+ measurements in the second resonance region. The experiment was performed at the ITEP accelerator at a positive pion beam momentum 1.43 GeV/c for scattering angles θcm = 127° and 133°. The setup was based on a polarized proton target and a carbon-plate polarimeter. The obtained data is compared with the predictions of the existing partial-wave analyses.

Measurement of the spin rotation parameters R and A in πp elastic scattering and a test of πN partial-wave analyses in the region of low-lying P11, S11 and D13 resonances

Abstract This paper presents the results of an experiment in which the spin rotation parameters R and Ain π − p elastic scattering have been measured at energies 450, 530, 560 and 600 MeV. The experiment was performed on a pion channel of the PNPI synchrocyclotron. The main parts of the setup were a polarized proton target with horizontal spin orientation and a carbon-plate polarimeter consisting of multigap optical spark chambers with television read-out. A comparison of the obtained results with partial-wave analyses is given.

Measurement of the polarization parameterP inπ+p elastic scattering in the region of low-lying pion-nucleon resonances

This paper presents the results of an experiment in which the polarization parameterP in π+p elastic scattering has been measured in the energy range from 335 to 580 MeV. The experiment was performed on a pion channel of the LNPI synchrocyclotron using a polarized proton target and wire spark chambers with magnetostrictive read-out. The results have substantially higher precision in comparison with the most of other experiments in this energy range and allow to determine unambiguously the shape of angular dependenceP(θ*) in the whole investigated region. New phase-shift analysis of π+p scattering data has been performed. The results of this experiment were used also to check isospin invariance.

Investigation of near-threshold eta-meson production in the reaction π − p→ ηn

Differential and total cross sections for eta-meson production in the reaction π−p → ηn were measured within the experimental program eta-meson physics implemented in the pion channel of the synchrocyclotron of the Petersburg Nuclear Physics Institute (PNPI, Gatchina). These measurements were performed at incident-pion momenta (700, 710, 720, and 730 MeV/c) in the vicinity of the threshold for the process under study by using the neutral-meson spectrometer designed and created at the Meson Physics Laboratory of PNPI. It is shown that, in the immediate vicinity of the threshold (685 MeV/c), the process of eta-meson production proceeds predominantly via S11(1535)-resonance formation followed by the decay S11(1535) → ηn (the respective branching fraction is Br ≈ 60%), but that, as the momentum of incident pions increases, the role of the D wave becomes ever more important. A detailed analysis of this effect indicates that it is due to the increasing contribution of the D13(1520) resonance. Although the branching fraction of the decay of this resonance through the ηn channel is assumed to be very small (BR ≈ 0.24%), the effect is enhanced owing to the interference between the D wave and the dominant resonance S11(1535).

Measurement of the spin rotation parameters R and A in π‐p‐elastic scattering in the region of pion‐nucleon resonances

First measurement of the spin rotation parameters R and A in {pi}-p elastic scattering in the region of pion-nucleon resonances has been performed at the Leningrad Nuclear Physics Institute. The experiment was carried out on a pion channel of the LNPI synchrocyclotron using a polarized target with LNPI synchrocyclotron using a polarized target with horizontally oriented polarization vector and a multi-plate carbon polarimeter consisting of optical spark chambers with television read-out. Results at the energies 450 and 560 MeV are given in comparison with the predictions of phase-shift analyses.

First measurement of the spin rotation parameters R and A in πp elastic scattering in the region of low-lying pion-nucleon resonances

The spin rotation parameters R and A in pi p elastic scattering have been measured for the first time in the energy range of low-lying pion-nucleon resonances. The experiment was carried out in a pion channel of the LNPI synchrocyclotron with negative pions of energy 450 MeV, using a polarised proton target with horizontally oriented spin and a carbon-plate polarimeter consisting of spark chambers with VDU read-out.

Recent results of the parameters A and R measurements in the resonance region of the πN‐elastic scattering and subsequent investigations.

The existing models of baryons usually predict considerably more resonance (three or more in number) than it was found by investigation of elastic pion‐nucleon scattering. This disagreement invites further investigation of the pion‐nucleon interaction and among other things the measurement of spin rotation parameters A and R in the elastic pion‐nucleon scattering.Recent experiments of the PNPI and PNPI‐ITEP collaborations resolved a part of twofold ambiguities of the existing partial wave analyses (PWA). These results were used in the last PWA of the George Washington University group SP06. The proposal for the additional spin rotation parameters A and R measurement in the resonance region is motivated. Such additional measurements are necessary to resolve remaining twofold ambiguities of the existing PWAs.

Semiempirical approach to P12c analyzing power description in the proton energy region TP = 400-1600MeV

Abstract In this report the proton-carbon scattering analyzing power data were summarized and reanalyzed on the base of analyzing power semi empirical description approach as superposition of elastic, qusielastic and inelastic processes. Our results cover the proton energy range Tp = 0.4-1.6GeV and the angular range θpc(lab.) = 5°-20°. They are compared with new experimental data in the region Tp = 0.9-1.3GeV, which were obtained at the ITEP accelerator.

Measurement of spin rotation parameter A+ in π +p elastic scattering

Abstract The ITEP-PNPI collaboration presents first results of the spin rotation parameter A+ measurements in the second resonance region. The experiment was performed on ITEP accelerator at positive pion beam momentum 1·43 GeV/c (√s= 1·90 GeV/c) for scattering angles 0cm = 127° and 133°. Main parts of the setup were a polarized proton target and a carbon-plate polarimeter. The results of measurements are in agreement with the predictions of the partial-wave analysis VPI and in contradiction with the predictions of PWAs KH and CMB.

Measurement of the Spin Rotation Parameters R and A in πp Elastic Scattering in the Energy Range from 450 to 600 MeV

Interest to the investigation of ℛP scattering in the resonance region has recently increased due to the development of various theoretical models predicting spectra of baryons. To make choice among these models one has to know baryon spectra with high precision.