Search

The polarization of the secondary protons in the (p, 2p) reaction with the S-shell protons of nuclei 4He, 6Li, 12C, 28Si, 40Ca was measured at 1 GeV unpolarized proton beam. The spin correlation parameters C ij for the 4He and 12C targets also were for the first time obtained as well. The polarization measurements were performed by means of a two-arm magnetic spectrometer, each arm of which was equipped with the multiwire-proportional chamber polarimeter. This experiment was aimed to study a modification of the proton-proton scattering matrix in the nuclear medium.

The analysis of high-precision ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}p$ cross-sectional data from the EPECUR Collaboration based on the multichannel $K$-matrix approach is presented. The sharp structures seen in these data are studied in terms of both opening thresholds and new resonance contributions. Some prominent features are found to be due to the opening $K\mathrm{\ensuremath{\Sigma}}$ channel. However, a complete description of the data is improved with the addition of two narrow resonant structures at $W\ensuremath{\sim}1.686$ and $W\ensuremath{\sim}1.720\phantom{\rule{4.pt}{0ex}}\mathrm{GeV}$. These structures are interpreted as manifestations of ${S}_{11}$ and ${P}_{11}$ resonances. The underlying nature of the observed phenomena is discussed.

The polarization correlation parameter Cnn in the elastic proton-proton scattering was for the first time measured with a high statistical accuracy at 1 GeV using an unpolarized proton beam incident on an unpolarized proton target. Both outgoing protons from the reaction were detected in coincidence by means of a two-arm focusing magnetic spectrometer installed at nonsymmetric angles corresponding to the center-of-mass scattering angle Θcm = 62.25°. The correlation parameter Cnn, as well as polarizations P1 and P2 of the secondary protons, were measured by means of multiwire proportional chamber polarimeters placed at the focal planes of each spectrometer arm. The obtained data are compared with the predictions of the phase-shift analysis. The connection with the experiment on Cnn and polarization measurements in the (p, 2p) reaction on 4He and other light nuclei in similar kinematics is discussed

The polarization of secondary protons from the (p, 2p) reaction induced by 1-GeV protons incident to a 4He nucleus was measured in a kinematically complete experiment. By using a two-arm magnetic spectrometer, two secondary protons from this reaction were recorded in coincidence at unequal scattering angles of Θ1 = 18°−24.21° and Θ2 = 53.22° over a broad range of the recoil-nucleus momentum K B between 0 and 150 MeV/c. It was found that the measured polarization of either secondary proton is less than that observed in free elastic proton-proton scattering. The magnitude of this difference is determined by the mean binding energy of s-shell protons rather than by the effective nuclear density. The polarizations measured in inclusive quasielastic and elastic scattering of 1-GeV protons on 4He nuclei are presented for scattering angles in the range Θ1 = 18° − 24.21°.

A program of measurement of the polarization parameter P in elastic {pi}{sup +}p interaction in the resonance region of backward pion scattering is presented. This program is aimed at determining the bifurcation points of the trajectory of zeros of the pion-nucleon amplitude and, hence, at unambiguously reconstructing the amplitude of {pi}N scattering in the second resonance region. It is planned to perform a relevant experiment in a pion beam from the accelerator of the Institute of Experimental and Theoretical Physics (ITEP, Moscow)

The SPIN-P experimental setup was designed for measuring the P asymmetry during pion scattering into the backward hemisphere at a minimum differential cross section of elastic πpscattering. The physical grounds of the experiment and the results of its simulation by the Monte Carlo method are presented. The setup is composed of a polarized proton target in a superconducting solenoid with vertical polarization of free protons, wire track detectors, scintillation counters, electronics for data readout and processing, and an appropriate computer network. The experimental program has been under way since 2002 on the pion beam of the proton synchrotron at the Institute of Theoretical and Experimental Physics (Moscow).

The polarization properties of elastic scattering are studied experimentally for pp interaction at 1 GeV. The respective experimental results are presented for the spin-transfer parameter Kn00n and the polarization Pn000 at c.m. angles of 22.5°, 27.5°, 32.5°, and 42.5° and for the analyzing power A000n at c.m. angles of 22.5° and 27.5°. The experiment employed an unpolarized proton beam from the accelerator of the Petersburg Nuclear Physics Institute, a polarized proton target, and a high-resolution magnetic spectrometer. The data from this experiment are analyzed and compared with the predictions of partial-wave analyses.

Experimental data on the spin-rotation parameters A and R in elasticπ+p interaction were obtained for the first time at a momentum of pπ = 1.62 GeV/c. These data are necessary for unambiguously reconstructing the amplitude of pion-nucleon scattering and, hence, for deducing a correct spectrum of nonstrange baryon resonances. In order to obtain results for the polarization parameters A and R with the minimum possible systematic error, the carbon polarimeter used was preliminarily calibrated in a dedicated experiment; that is, the analyzing power was measured in proton-carbon scattering for incidentproton energies in the range Tp=0.7–1.3 GeV. The experimental data reported in the present article were obtained by a collaboration of researchers from the Petersburg Nuclear Physics Institute and Institute of Theoretical and Experimental Physics (ITEP, Moscow) at the ITEP synchrotron.

The spin rotation parameters A and R were measured for the elastic pion-proton scattering by the PNPI-ITEP collaboration in the D13 (1700), ΔS31(1900), ΔP33(1920) and ΔD33 (1940) resonances region. These resonances were absent in the set of partial wave analysis (PWA) of the Virginia Polytechnic Institute group (VPI), but was included in the tables of the Review of Particle Physics. The main goal of the experimental program was to resolve the current PWA’s disagreement in spin rotation parameters value predictions. Simultaneously with A and R the polarization parameter P was measured with the purpose to improve the experimental data base and estimate the experimental systematic errors. Our results for spin rotation parameters A and |R| are in agreement with PWA VPI predictions.

The results of measurements of the spin transfer parameter Knoon as well as of the analyzing power Aooon and polarization Pnooo in the pp-elastic scattering at 1 GeV are presented. The data were obtained in the angular range 20–40° c.m. The experiment has been performed at PNPI 1 GeV proton accelerator using the proton polarized target and the high resolution magnetic spectrometer. The last one was especially adopted to work with the “thick” polarized target made of propandiol. The measurements of the Knoon parameter in this angular and energy region were carried out for the first time. The results are compared with the pp-scattering phase shift analysis predictions.

New experimental data on the spin-rotation parameters A and R measured for elastic π ± p scattering in the resonance region and on the asymmetry in pC scattering at primary momenta in the range 1.35–2.02 GeV/c, as well as in quasielastic proton scattering on nuclei in the same momentum range, are summarized. All these data were recently obtained by using the proton synchrotron installed at the Institute of Theoretical and Experimental Physics (ITEP, Moscow). The spectrum and features of seven isospin-3/2 baryon resonances that form a peak in the total cross section at a c.m. energy of 1.9 GeV are analyzed on the basis of new data on the parameters A and R, and the results of this analysis are presented. The experiments surveyed in this article were performed by a collaboration of researchers from ITEP and the Petersburg Nuclear Physics Institute (PNPI, Gatchina), the ITEP-PNPI collaboration.

The spin rotation parameters A and R were measured for the elastic pion-proton scattering by the PNPI-ITEP collaboration in the D13(1700) resonance region. The main goal of the experimental program is to resolve the current partial-wave analyses (PWA) uncertainties. Simultaneously with A and R the polarization parameter P was measured with the purpose to improve the experimental database and estimate systematic errors. The constraint which demands a smooth energy dependence of all π-p transverse amplitude zeros in the complex plane together with the new experimental data on A parameter can lead to the conclusion that the Barrelet branch of “zero trajectories" is chosen improperly in PWA of the Carnegie-Mellon-Lawrence-Berkely-Laboratory groups at the range of the pion beam momentum near 1.0 GeV/c. The setup included a longitudinally polarized proton target with superconductive magnet, multiwire spark chambers and carbon polarimeter with thick filter. The experiment was performed at the ITEP proton synchrotron, Moscow.

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 PWA's KH and CMB.

Results of the total cross section differenceΔσL in anp transmission experiment at 1.19, 2.49 and 3.65 GeV incident neutron beam kinetic energies are presented. Measurements were performed at the Synchrophasotron of the Laboratory of High Energies of the Joint Institute for Nuclear Research in Dubna. Results were obtained with a polarized beam of free quasi-monochromatic neutrons passing through the new Dubna frozen spin proton target. The beam and target polarizations were oriented longitudinally. The present results were obtained at the highest energies of free polarized neutrons that can be reached at present. They extend the energy range of existing results from PSI, LAMPF and Saclay measured between 0.066 and 1.10 GeV. The new results are compared withΔσL(pn) data determined as a difference betweenΔσL(pd) andΔσL(pp) ANL-ZGS measurements. The values ofΔσL for the isospin stateI=0 were deduced using knownpp data.

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.

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.

The main goal of this proposal is the search for a narrow cryptoexotic nucleon resonance by scanning of the pi- p system invariant mass in the region (1610-1770) MeV with the detection of pi- p and K Lambda decays. The scan is supposed to be done by the variation of the incident pi- momentum and its measurement with the accuracy of up to +-0.1% (better than 1 MeV in terms of the invariant mass in the whole energy range) with a set of proportional chambers located in the first focus of the magnetooptical channel. High sensitivity of the method to the resonance under search is shown. The secondary particles scattered from a liquid hydrogen target are detected by sets of the wire drift chambers equipped with modern electronics. The time scale of the project is about 3 years. The budget estimate including manpower, the apparatus and operation cost, is about 40 million rubles. The beam time required is (4-6) two week runs on "high" (10 GeV/c) flattop of the ITEP proton synchrotron.

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.

The asymmetry parameter P was measured for the elastic pion-proton scattering in the very backward angular region of theta_cm ~ 150-170^o at several pion beam energies in the invariant mass range containing most of the pion-proton resonances. The general goal of the experimental program was to provide new data for partial wave analyses in order to resolve their uncertainties in the baryon resonance region to allow the unambiguous baryon spectrum reconstructions. Until recently the parameter P was not measured in the examined domain that might be explained by the extremely low cross section. At the same time the predictions of various partial wave analyses are far from agreement in some kinematic areas and specifically those areas were chosen for the measurements where the disagreement is most pronouncing. The experiment was performed at the ITEP U-10 proton synchrotron, Moscow, by the ITEP-PNPI collaboration in the latest 5 years., Comment: 6 pages, 5 figures. to be submitted to the European Physical Journal

Latest results by the ITEP‐PNPI collaboration on the asymmetry in the π+p elastic scattering are presented. The data were obtained for the first time in the region of backward angles with low cross section, where the predictions of the partial wave analyses are not reliable. The results at 1.94 GeV/c are in favor of the older KH80 analysis and show noticeable deviation from the latest FA06 solution by GWU group. At 2.07 GeV/c very low cross section did not allow to achieve good accuracy. Yet the data do not follow any of the PWA predictions and definitely disagree with SP06 analysis.

The idea of ‘EPECUR’ was inspired by the recent splash of the activity around the pentaquark matters. The goal of the experiment is the search for narrow resonant states in the reactions π−p → π−p and π−p → K0Λ based on the very precise cross section measurements in fine energy steps of 0.5 MeV in terms of the invariant mass. As a valuable byproduct of the second stage of the experiment, Λ‐polarization in π−p → K0Λ can be measured, based on the well‐known weak Λ‐decay asymmetry. The expected statistical significance of the measurement overrides the best existing data from ‘NIMROD’ detector by an order of magnitude. The experimental setup is under construction at the ITEP proton synchrotron in collaboration with PNPI and ACU.

The ITEP-PNPI collaboration presents new results of the measurements of the spin rotation parameter A in the elastic scattering of negative pions on protons at P_beam=1.43 GeV/c. The results are compared to the predictions of several partial wave analyses. The experiment was performed at the ITEP proton synchrotron, Moscow., 4 pages, 5 figures

The paper presents new experimental data on the spin rotation parameter A obtained recently by ITEP‐PNPI collaboration at the ITEP accelerator. The set of measurements was performed in carefully chosen critical points with precision sufficient for choosing the correct branches of partial wave analyses. The data for both π+ and π−‐scattering at 1.0, 1.43 and 1.62 GeV/c is included.

One of the main sources of the information about nuclear resonances are partial wave analyses (PWA) of pion-proton elastic scattering. Nearly all of the data available for PWA were obtained more than 20 years ago with old measurement techniques. The talk presents new high precision data obtained recently by the EPECUR collaboration. The experiment features high statistics and better than 1 MeV resolution in the invariant mass thus allowing searches for narrow resonances with the coupling to the πp channel as low as 5%. The experimental setup consists of a 25 cm long liquid hydrogen target in a non-magnetic spectrometer of wire drift chambers with hexagonal structure. The measurements started in 2009. 3 billions of triggers are already collected with positive and negative pion beams in the beam momentum range 820-1330 MeV/c.

The EPECUR collaboration presents new high precision data on the pion- proton elastic scattering in the second resonance region. The experiment EPECUR is placed on the universal beam channel of the accelerator ITEP. The setup features 0.1% beam pion momentum tagging system, 25 cm long liquid hydrogen target, placed in my- lar container and beryllium outer shell, low material wire drift chambers and high perfor- mance DAQ. More than 3 billions of triggers have been collected. The data cover pion beam momentum range 0.8 - 1.3 GeV/c and 40-120 degrees center-of-mass scattering angle range for both positive and negative pions. The measured differential cross section has 2% statistical accuracy in 2 degrees angle and 5 MeV/c momentum intervals.

The ITEP-PNPI collaboration presents the results of the measurements of the spin rotation parameter A in the elastic scattering of positive and negative pions on protons at P_beam = 1.62 GeV/c. The setup included a longitudinally-polarized proton target with superconductive magnet, multiwire spark chambers and a carbon polarimeter with thick filter. Results are compared to the predictions of partial wave analyses. The experiment was performed at the ITEP proton synchrotron, Moscow., 7 pages, 3 figures. To be published in Phys. Lett. B

A description of the recently installed mouable Polarized Proton Targe (MPT) at the JINR in Dubna is described. This target was acquired from Fermilab. The physics program based on the MPT at Dbna is outlined. (AIP)

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.

The results of the measurements of the spin-spin correlation parameter CNN in the energy region 0. 69–0. 95 GeV are presented.

This paper presents the results of an experiment in which the polarization parameter P in π − p elastic scattering has been measured at energies of 450, 490, 530, 560 and 600 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 other experiments in this energy range.

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.

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.

First measurement of the spin rotation parameters R and A in π‐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.