The vector analyzing power Ay for the reaction Full-size image (<1 K) has been measured at five angles between 60° and 140° in the lab at an incident neutron energy of 67.7 MeV. The measurement is of a presision never before acheived (ΔAy ⩽ 0.01, statistical) for this observable. This precision makes possible a quantitative comparison with meson-exchange theories, thus enhancing our understanding of the role of non-nucleonic degrees of freedom.
No description provided.
A measurement of the spin correlation parameters A xx (90° cm) and A yy (90° cm) of 47.5 MeV proton-proton scattering has been performed by means of polarized beam and a polarized target.
No description provided.
The polarization of the recoil proton in γ + p → p + π0 has been measured at photon energies of 725 MeV and 900 MeV for centerof-mass angles near 90° using a small propane-ethane gas bubble chamber. Protons emerging from a liquid hydrogen target are momentum-analysed with a magnet, and the scattering from carbon observed in the bubble chamber. A counter telescope rejects pions and electrons, and protons from multiple pion processes are discriminated against by keeping the peak bremsstrahlung energy just above the mean photon energy. The visual method of observing scattering asymmetries has the advantage of being insensitive to systematic asymmetries in the incoming proton flux. It also quickly eliminates strongly inelastic scatters (stars), and provides a complete angular distribution from which the fraction of scatters which are inelastic can be deduced. The effect of inelastic scatters upon the scattering asymmetry is large when the energy-loss resolution is poor, an inherent problem with bremsstrahlung beams. The counting rate for this small chamber (3.4g/cm2 carbon scatterer) was 11 scatters/hour using every 5th synchrotron pulse; larger chambers with more dense scatterers (such as Freon) could give higher counting rates. Results are fork = 725MeV and ϑ (pion) = 87° (cm.), P=0.74±0.20, and for k=900MeV and ϑ (pion) = 70°, P=.51±.7. P is taken to be positive along the directionK xp, wherep is the momentum of the outgoing proton.
No description provided.
The polarization observable I^s, a feature exclusive to the acoplanar kinematics of multi-meson final states produced via linearly polarized photons, has been measured for the first time. Results for the reaction g p -> p pi0 eta are presented for incoming photon energies between 970 MeV and 1650 MeV along with the beam asymmetry I^c. The comparably large asymmetries demonstrate a high sensitivity of I^s to the dynamics of the reaction. Fits using Bonn-Gatchina partial wave analysis demonstrate that the new polarization observables carry significant information on the contributing partial waves.
Measured beam asymmetry I_S as a function of the angle between the reaction plane and the plane of the two final state particles with the the proton as the recoiling particle for the cm energy range 1642 to 1770 MeV.
Measured beam asymmetry I_S as a function of the angle between the reaction plane and the plane of the two final state particles with the the proton as the recoiling particle for the cm energy range 1770 to 1898 MeV.
Measured beam asymmetry I_S as a function of the angle between the reaction plane and the plane of the two final state particles with the the proton as the recoiling particle for the cm energy range 1898 to 1994 MeV.
We present measurements of the differential cross section and Lambda recoil polarization for the gamma p to K+ Lambda reaction made using the CLAS detector at Jefferson Lab. These measurements cover the center-of-mass energy range from 1.62 to 2.84 GeV and a wide range of center-of-mass K+ production angles. Independent analyses were performed using the K+ p pi- and K+ p (missing pi -) final-state topologies/ results from these analyses were found to exhibit good agreement. These differential cross section measurements show excellent agreement with previous CLAS and LEPS results and offer increased precision and a 300 MeV increase in energy coverage. The recoil polarization data agree well with previous results and offer a large increase in precision and a 500 MeV extension in energy range. The increased center-of-mass energy range that these data represent will allow for independent study of non-resonant K+ Lambda photoproduction mechanisms at all production angles.
Differential cross section as a function of COS(THETA(K)) for the centre-of-mass range 1.62-1.63 GeV.
Differential cross section as a function of COS(THETA(K)) for the centre-of-mass range 1.63-1.64 GeV.
Differential cross section as a function of COS(THETA(K)) for the centre-of-mass range 1.64-1.65 GeV.
At the electron accelerator ELSA a linearly polarised tagged photon beam is produced by coherent bremsstrahlung off a diamond crystal. Orientation and energy range of the linear polarisation can be deliberately chosen by accurate positioning of the crystal with a goniometer. The degree of polarisation is determined by the form of the scattered electron spectrum. Good agreement between experiment and expectations on basis of the experimental conditions is obtained. Polarisation degrees of P = 40% are typically achieved at half of the primary electron energy. The determination of P is confirmed by measuring the beam asymmetry, \Sigma, in pi^0 photoproduction and a comparison of the results to independent measurements using laser backscattering.
Beam asymmetry as a function of the PI0 centre of mass scattering angle.
Beam asymmetry as a function of the PI0 centre of mass scattering angle.
Beam asymmetry as a function of the PI0 centre of mass scattering angle.
In photoproduction experiments, a large number of final states yielding various resonance contributions are accessible. To extract resonance parameters via partial-wave analysis not only the measurement of differential cross-sections is necessary, but also the determination of polarization observables. At the electron accelerator ELSA (Bonn) the coherent bremsstrahlung method was used to generate a linearly polarized photon beam. Using the CBELSA/TAPS detector setup, the beam asymmetry Σ in the reaction γp → pπ 0 η was determined as a function of various masses and angles for photon energies between 970MeV and 1650MeV.
Measured beam asymmetry as a function of the cosine of the scattered proton angle for beam energies 0.970 to 1.200 GeV.
Measured beam asymmetry as a function of the cosine of the scattered proton angle for beam energies 1.200 to 1.450 GeV.
Measured beam asymmetry as a function of the cosine of the scattered proton angle for beam energies 1.450 to 1.650 GeV.
Cross sections for the $\gamma p \to K^+ \Lambda$ have been measured at backward angles using linearly polarized photons in the range 1.50 to 2.37 GeV. In addition, the beam asymmetry for this reaction has been measured for the first time at backward angles. The $\Lambda$ was detected at forward angles in the LEPS spectrometer via its decay to $p\pi^-$ and the K^+ was inferred using the technique of missing mass. These measurements, corresponding to kaons at far backward angles in the center-of-mass frame, complement similar CLAS data at other angles. Comparison with theoretical models shows that the reactions in these kinematics provide further opportunities to investigate the reaction mechanisms of hadron dynamics.
Differential cross sections as a function of the Mandelstam variable U for photon beam energy 1.5 to 1.8 GeV.
Differential cross sections as a function of the Mandelstam variable U for photon beam energy 1.8 to 2.1 GeV.
Differential cross sections as a function of the Mandelstam variable U for photon beam energy 2.1 to 2.4 GeV.
The beam asymmetry, $\Sigma$, was measured at ELSA in the reaction $\vec \gamma p \to \eta p$ using linearly polarised tagged photon beams, produced by coherent bremsstrahlung off a diamond. The crystal was oriented to provide polarised photons in the energy range $E_\gamma = 800$ to 1400 MeV with the maximum polarisation of $P_\gamma = 49$ % obtained at 1305 MeV. Both dominant decay modes of the $\eta$ into two photons and $3\pi^0$ were used to extract the beam asymmetry from the azimuthal modulation of the cross section. The measurements cover the angular range $\Theta_\text{cm}\simeq 50$ -- 150 degrees. Large asymmetries up to 80 % are observed, in agreement with a previous measurement. The eta-MAID model and the Bonn--Gatchina partial wave analysis describe the measurements, but the required partial waves differ significantly.
Photon asymmetry for eta photoproduction at incident photon energy of 850 MeV.
Photon asymmetry for eta photoproduction at incident photon energy of 950 MeV.
Photon asymmetry for eta photoproduction at incident photon energy of 1050 MeV.
We report measurements of the exclusive electroproduction of $K^+\Lambda$ and $K^+\Sigma^0$ final states from a proton target using the CLAS detector at the Thomas Jefferson National Accelerator Facility. The separated structure functions $\sigma_T$, $\sigma_L$, $\sigma_{TT}$, and $\sigma_{LT}$ were extracted from the $\Phi$- and $\epsilon$-dependent differential cross sections taken with electron beam energies of 2.567, 4.056, and 4.247 GeV. This analysis represents the first $\sigma_L/\sigma_T$ separation with the CLAS detector, and the first measurement of the kaon electroproduction structure functions away from parallel kinematics. The data span a broad range of momentum transfers from $0.5\leq Q^2\leq 2.8$ GeV$^2$ and invariant energy from $1.6\leq W\leq 2.4$ GeV, while spanning nearly the full center-of-mass angular range of the kaon. The separated structure functions reveal clear differences between the production dynamics for the $\Lambda$ and $\Sigma^0$ hyperons. These results provide an unprecedented data sample with which to constrain current and future models for the associated production of strangeness, which will allow for a better understanding of the underlying resonant and non-resonant contributions to hyperon production.
Cross sections for incident energy 2.567 GeV for the Q**2 range 0.5 to 0.8 GeV**2 and W range 1.6 to 1.7 GeV.
Cross sections for incident energy 2.567 GeV for the Q**2 range 0.5 to 0.8 GeV**2 and W range 1.70 to 1.75 GeV.
Cross sections for incident energy 2.567 GeV for the Q**2 range 0.5 to 0.8 GeV**2 and W range 1.75 to 1.80 GeV.
Spin transfer from circularly polarized real photons to recoiling hyperons has been measured for the reactions $\vec\gamma + p \to K^+ + \vec\Lambda$ and $\vec\gamma + p \to K^+ + \vec\Sigma^0$. The data were obtained using the CLAS detector at Jefferson Lab for center-of-mass energies $W$ between 1.6 and 2.53 GeV, and for $-0.85<\cos\theta_{K^+}^{c.m.}< +0.95$. For the $\Lambda$, the polarization transfer coefficient along the photon momentum axis, $C_z$, was found to be near unity for a wide range of energy and kaon production angles. The associated transverse polarization coefficient, $C_x$, is smaller than $C_z$ by a roughly constant difference of unity. Most significantly, the {\it total} $\Lambda$ polarization vector, including the induced polarization $P$, has magnitude consistent with unity at all measured energies and production angles when the beam is fully polarized. For the $\Sigma^0$ this simple phenomenology does not hold. All existing hadrodynamic models are in poor agreement with these results.
Coefficients Cx and Cz for the reaction GAMMA P --> K+ LAMBDA for incident energy = 1.032 GeV and W = 1.679 GeV.
Coefficients Cx and Cz for the reaction GAMMA P --> K+ LAMBDA for incident energy = 1.132 GeV and W = 1.734 GeV.
Coefficients Cx and Cz for the reaction GAMMA P --> K+ LAMBDA for incident energy = 1.232 GeV and W = 1.787 GeV.
Differential cross sections and photon beam asymmetries have been measured for the gamma n -> K+ Sigma- and gamma p -> K+ Sigma0 reactions separately using liquid deuterium and hydrogen targets with incident linearly polarized photon beams of Egamma=1.5-2.4 GeV at 0.6<cosTheta<1. The cross section ratio of sigma(K+Sigma-)/sigma(K+Sigma0), expected to be 2 on the basis of the isospin 1/2 exchange, is found to be close to 1. For the K+Sigma- reaction, large positive asymmetries are observed indicating the dominance of the K*-exchange. A large difference between the asymmetries for the K+Sigma- and K+Sigma0 reactions can not be explained by simple theoretical considerations.
Differential cross section for GAMMA P --> K+ SIGMA0.. Errors are statistical only.
Photon beam asymmetry for GAMMA N --> K+ SIGMA-.. Errors are statistical only.
Photon beam asymmetry for GAMMA P --> K+ SIGMA0.. Errors are statistical only.
Differential cross sections and photon beam asymmetries for the gamma p rightarrow K+ Lambda and gamma p rightarrow K+ Sigma0 reactions have been measured in the photon energy range from 1.5 GeV to 2.4 GeV and in the angular range from Theta_{cm} = 0 to 60 of the K+ scattering angle in the center of mass system at the SPring-8/LEPS facility. The photon beam asymmetries for both the reactions have been found to be positive and to increase with the photon energy. The measured differential cross sections agree with the data measured by the CLAS collaboration at cosTheta_{cm}<0.9 within the experimental uncertainties, but the discrepancy with the SAPHIR data for the K+Lambda reaction is large at cosTheta_{cm}>0.9. In the K+Lambda reaction, the resonance-like structure found in the CLAS and SAPHIR data at W=1.96 GeV is confirmed. The differential cross sections at forward angles suggest a strong K-exchange contribution in the t-channel for the K+Lambda reaction, but not for the K+Sigma0 reaction.
Photon beam asymmetries for the two reactions as a function of CM angle for photon beam energy 1.55 GeV (W=1.947 GeV).
Photon beam asymmetries for the two reactions as a function of CM angle for photon beam energy 1.65 GeV (W=1.994 GeV).
Photon beam asymmetries for the two reactions as a function of CM angle for photon beam energy 1.75 GeV (W=2.041 GeV).
The reaction gamma p --> K0 Sigma+ was measured in the photon energy range from threshold up to 2.6 GeV with the SAPHIR detector at the electron stretcher facility, ELSA, in Bonn. Results are presented on the reaction cross section and the polarization of the Sigma+ as a function of the kaon production angle in the centre-of-mass system, cos(Theta_K^{c.m.}), and the photon energy. The cross section is lower and varies less with photon energy and kaon production angle than that of gamma p --> K+ Sigma0. The Sigma+ is polarized predominantly at cos(Theta_K^{c.m.}) \approx 0. The data presented here are more precise than previous ones obtained with SAPHIR and extend the photon energy range to higher values. They are compared to isobar model calculations.
Axis error includes +- 10/10 contribution (Normalization uncertainty already included.).
Axis error includes +- 10/10 contribution (Normalization uncertainty already included.).
Axis error includes +- 10/10 contribution (Normalization uncertainty already included.).
The exclusive omega electroproduction off the proton was studied in a large kinematical domain above the nucleon resonance region and for the highest possible photon virtuality (Q2) with the 5.75 GeV beam at CEBAF and the CLAS spectrometer. Cross sections were measured up to large values of the four-momentum transfer (-t < 2.7 GeV2) to the proton. The contributions of the interference terms sigma_TT and sigma_TL to the cross sections, as well as an analysis of the omega spin density matrix, indicate that helicity is not conserved in this process. The t-channel pi0 exchange, or more generally the exchange of the associated Regge trajectory, seems to dominate the reaction gamma* p -> omega p, even for Q2 as large as 5 GeV2. Contributions of handbag diagrams, related to Generalized Parton Distributions in the nucleon, are therefore difficult to extract for this process. Remarkably, the high-t behaviour of the cross sections is nearly Q2-independent, which may be interpreted as a coupling of the photon to a point-like object in this kinematical limit.
Total cross sections and interference terms (TT and TL).
Differential cross sections DSIG/DT for Q**2 = 1.725 GeV**2 and W = 2.77 GeV.
Differential cross sections DSIG/DT for Q**2 = 1.752 GeV**2 and W = 2.48 GeV.
Reaction K−p→π0π0Λ was measured at eight incident K− momenta between 514 and 750MeV∕c using the Crystal Ball multiphoton spectrometer. The reaction dynamics are displayed in total cross sections, Dalitz plots, invariant-mass spectra, production angular distributions, and the Λ polarization. The π0π0Λ production is dominated by the π0Σ0(1385) intermediate state; no trace of other light Σ∗ states is observed, and the role of the f0(600) meson appears to be insignificant. A striking similarity is seen between K−p→π0π0Λ and π−p→π0π0n; this can be understood as a consequence of dynamical flavor symmetry.
Measured cross section. Statistical errors only.
Differential cross section for the di-pion system in the c.m. system for incident momenta 514 to 629 MeV.
Differential cross section for the di-pion system in the c.m. system for incident momenta 659 to 750 MeV.
Analyzing powers of pion-proton elastic scattering have been measured at PSI with the Low Energy Pion Spectrometer LEPS as well as a novel polarized scintillator target. Angular distributions between 40 and 120 deg (c.m.) were taken at 45.2, 51.2, 57.2, 68.5, 77.2, and 87.2 MeV incoming pion kinetic energy for pi+ p scattering, and at 67.3 and 87.2 MeV for pi- p scattering. These new measurements constitute a substantial extension of the polarization data base at low energies. Predictions from phase shift analyses are compared with the experimental results, and deviations are observed at low energies.
Analyzing power for PI+ P elastic scattering at incidient kinetic energy 87.2 MeV from the data set 1.
Analyzing power for PI+ P elastic scattering at incidient kinetic energy 68.4 MeV from the data set 1.
Analyzing power for PI+ P elastic scattering at incidient kinetic energy 57.2 MeV from the data set 1.
None
No description provided.
Beam polarization asymmetries for the p(gamma,K+)Lambda and p(gamma,K+)sigma0 reactions are measured for the first time for Egamma=1.5-2.4 GeV and 0.6<cos(theta_cm(K+))<1.0 by using linearly polarized photons at the Laser-Electron-Photon facility at SPring-8 (LEPS). The observed asymmetries are positive and gradually increase with rising photon energy. The data are not consistent with theoretical predictions based on tree-level effective Lagrangian approaches. Including the new results in the development of the models is, therefore, crucial for understanding the reaction mechanism and to test the presence of baryon resonances which are predicted in quark models but are sofar undiscovered.
Measured beam asymmetries for the reaction GAMMA P --> K+ LAMBDA for beam energy 1.5 to 1.6.
Measured beam asymmetries for the reaction GAMMA P --> K+ LAMBDA for beam energy 1.6 to 1.7.
Measured beam asymmetries for the reaction GAMMA P --> K+ LAMBDA for beam energy 1.7 to 1.8.
We present a measurement of the polarization of Antilambda hyperons produced in nu_mu charged current interactions. The full data sample from the NOMAD experiment has been analyzed using the same V0 identification procedure and analysis method reported in a previous paper for the case of Lambda hyperons. The Antilambda polarization has been measured for the first time in a neutrino experiment. The polarization vector is found to be compatible with zero.
Lambdabar polarization in regions of Feynman X (XL).
Lambdabar polarization in regions of the Bjorken scaling variable X.
We present measurements of the differential and total cross sections and the Λ polarization for the reaction K−p→ηΛ from threshold to pK−=770MeV/c, with much better precision than previous measurements. Our cross-section data show a remarkable similarity to the SU(3) flavor-related π−p→ηn cross-section results. The reaction K−p→ηΛ at threshold is dominated by formation of the intermediate Λ(1670)12− state.
Total cross section measurement for K- P --> ETA LAMBDA. Errors shown are statistical only.
Differential cross sections DSIG/DOMEGA for K- P --> ETA LAMBDA. Errors shown are statistical only.
Differential cross sections DSIG/DOMEGA for K- P --> ETA LAMBDA. Errors shown are statistical only.
Polarization transfer in the 4He(e,e'p)3H reaction at a Q^2 of 0.4 (GeV/c)^2 was measured at the Mainz Microtron MAMI. The ratio of the transverse to the longitudinal polarization components of the ejected protons was compared with the same ratio for elastic ep scattering. The results are consistent with a recent fully relativistic calculation which includes a predicted medium modification of the proton form factor based on a quark-meson coupling model.
No description provided.
No description provided.
We report the first measurement of the vector analyzing power in inclusive transversely polarized elastic electron-proton scattering at Q^2 = 0.1 (GeV/c)^2 and large scattering angles. This quantity should vanish in the single virtual photon exchange, plane wave impulse approximation for this reaction, and can therefore provide information on double photon exchange amplitudes for electromagnetic interactions with hadronic systems. We find a non-zero value of A=-15.4+/-5.4 ppm. No calculations of this observable for nuclei other than spin 0 have been carried out in these kinematics, and the calculation using the spin orbit interaction from a charged point nucleus of spin 0 cannot describe these data.
Polarized beam.
The reaction γp → K 0 Σ + has been measured with the SAPHIR detector at the electron stretcher ring ELSA. The total cross section rises up to a peak value of 1.1 μ b at a photon energy of 1.4 GeV. The differential cross sections dσ/dΩ are consistent with being flat throughout the measured energy range. The first measurement of the Σ + polarization in photon induced reactions was obtained.
Total cross section for the reaction GAMMA P --> K0 SIGMA+. Errors include statistics and the uncertainty on the acceptance calculation and photon flux.
Differential cross section for the reaction GAMMA P --> K0 SIGMA+. Errors are dominated by statistical uncertainties.
Measure of SIGMA+ polarization in the reaction GAMMA P --> K0 SIGMA+.
Analyzing powers for p→n→pp(S01)π− were measured at beam energies 353, 404, and 440 MeV by extracting the quasifree process from p→d→pppπ−. Partial wave amplitude analysis yields a significant contribution from the isospin 1, s-wave channel. This contribution is relatively much larger than that expected from theoretical models which have been successful in describing the isospin 1, s-wave channel behavior of pp→ppπ0 cross sections at threshold.
Axis error includes +- 0.0/0.0 contribution (?////).
Axis error includes +- 0.0/0.0 contribution (?////).
Axis error includes +- 0.0/0.0 contribution (?////).
High quality analyzing powers for the π−p→→π0n reaction have been obtained with a polarized proton target over a broad angular range at incident kinetic energies of 98.1, 138.8, 165.9, and 214.4 MeV. This experiment nearly doubled the existing πN single-charge-exchange database for energies ranging from 10 to 230 MeV, with 36 new analyzing powers. The Neutral Meson Spectrometer was used to detect the outgoing neutral pions. The data are well described by recent phase-shift analyses. When combined with high-precision and accurate cross section data at the same energies, the data can provide a good test of the degree of isospin breaking in the region of the Δ(1232) resonance. They will also be helpful for constraining the evaluation of the pion-nucleon σ term from the scattering amplitudes.
First error is total uncertainty.
First error is total uncertainty.
First error is total uncertainty.
Associated strangeness production in the reactions γp → K + Λ and γp → K + Σ 0 was measured with the SAPHIR detector at the electron stretcher ring ELSA at Bonn. Data on total and differential cross sections and on hyperon polarizations are presented. The total cross section for Λ production shows a strong threshold enhancement whereas the Σ 0 data have a maximum at about E γ =1.45 GeV. Along with the angular decomposition of the differential cross section into polynomials, this suggests resonance production. However, the angular distributions of both hyperon polarizations vary only slightly with the photon energy. Λ and Σ 0 polarizations show opposite signs and change sign over the angular range.
Total cross section for the reaction GAMMA P --> K+ LAMBDA.
Total cross section for the reaction GAMMA P --> K+ SIGMA0.
Differential cross section for the reaction GAMMA P --> K+ LAMBDA in the GAMMA energy range 0.90 to 1.10 GeV in three energy bins.
The analyzing power Ay for π+p→ scattering at 68.3 MeV has been measured at the Paul Scherrer Institut with the magnetic spectrometer LEPS. The measurements cover the angular range 40°≤θlab≤70°. The protons have been polarized in a butanol target, operated in frozen spin mode. The S31 phase shift comes out by about 1° smaller than the Koch-Pietarinen [Nucl. Phys. A 336, 331 (1980)] phase shift analysis, supporting the necessity of an alternative dispersion analysis of πN scattering to determine the σ term and the πN coupling constant. © 1996 The American Physical Society.
The two data sets correspond to measurements with two different target compositions (see text).
The depolarization parameter Donon of the p dash p → n dash n charge exchange reaction has been measured for the first time at the CERN Low Energy Antiproton Ring (LEAR) at two antiproton momenta, 546 and 875 MeV/ c . The transverse polarization of the recoil neutron was analyzed using a large-acceptance neutron polarimeter made up of two parallel plastic scintillator planes. D 0 n 0 n is usually less than 0.35 which suggests that the spin-spin amplitudes dominate in the scattering matrix. Results are compared with the predictions of various N dash N potential models. The agreement is in general satisfactory.
No description provided.
No description provided.
The measurement of the polarisation transfer to the proton in the reactions\(H(\vec e,e'\vec p)\) and\(D(\vec e,e'\vec p)\) performed with longitudinally polarised electrons in quasi-free kinematics is presented. The coincidence measurement was executed atQ2≈8fm−2 using the 855 MeV, c.w. beam of the Mainz Microtron MAMI. The recoil polarisation was determined by means of a carbon analyser. The experiment shows that the binding of the nucleon does not modify the polarisationPx of the recoil proton within an error ofΔPx/Px≈10%. The measured polarisation agrees with recent theoretical predictions. Implications for the measurement of the electric form factor of the neutron using the\(D(\vec e,e'\vec n)\) reaction are discussed.
No description provided.
The reactions γp→K+ Λ and γp→K+ Σ0 have been measured with the multiparticle detector system SAPHIR at ELSA in Bonn. Besides the differential cross sections the Λ polarization and, for the first time, the Σ0 polarization have been determined in a photon induced reaction. All data are presented as functions of the photon energy (from threshold up to 1.47 GeV) and of the kaon production angle (0°–180°). The polarization of both Λ and Σ0 is substantial at all energies and varies strongly with the production angle.
Differential cross sections.
Total cross sections.
Differential cross sections.
Final results of the measurement of the analysing power A On of the p p → n n reaction are presented. Eight measurements in the range 546–1287 MeV/ c incoming p momentum have been performed over the full angular range using a solid polarized proton target and the Low Energy Antiproton Ring (LEAR) at CERN antiproton extracted beams.
No description provided.
No description provided.
No description provided.
Analysing powers and differential cross sections for p p → π − π + and p p → K − K + have been measured over the full angular range using a polarised target at LEAR at 20 beam momenta from 360 to 1550 MeV/ c . Discrepancies in the normalisation of earlier d σ/ d Ω data at low momenta are clarified. Above 1000 MeV/ c , A 0N results confirm values close to +1 over most of the angular range for both reactions, in excellent agreement with earlier data of lower statistics. Below 1000 MeV/ c , where the analysing power is measured for the first time, large variations of A 0N with energy and angle are present.
No description provided.
No description provided.
No description provided.
Results are given for the analysing power of the p ̄ p→ n ̄ n charge-exchange reaction at four incident beam momenta. The measurement is part of an experimental programme to study the spin structure of this reaction at LEAR. The analyzing power shows strong angular and energy dependence, which at present is not reproduced by the existing meson-exchange potential models.
No description provided.
No description provided.
No description provided.
The angular distributions of the analyzing power A y and of the differential cross section d σ/ d Ω in p p elastic scattering have been measured at 439 and 544 MeV/c. The results of A y are compared with various theoretical models.
Data requested from authors.
Legendre fit polynomials.
Normalized Legendre fit polynomials.
The depolarization parameter D onon in p p elastic scattering has been measured at LEAR for thirteen momenta between 679 and 1550 MeV/c in the backward angular region. Striking disagreement with theoretical models is observed.
No description provided.
No description provided.
No description provided.
As part of a programme to study the spin structure of the p p→ n n channel, we have measured the analysing power A 0 n and the differential cross section at an incident antiproton beam momentum of 704 MeV/ c . The analysing power exhibits a remarkable angular dependence, which is poorly reproduced by the existing potential models.
No description provided.
No description provided.
First data are presented for the polarized-target asymmetry in the reaction π+p→π+pγ at an incident pion energy of 298 MeV. The geometry was chosen to maximize the sensitivity to the radiation of the magnetic dipole moment μΔ of the Δ++(1232 MeV). A fit of the asymmetry in the cross section d5σ/dΩπ dΩγ dk as a function of the photon energy k to predictions from a recent isobar-model calculation with μΔ as the only free parameter yields μΔ=1.64(±0.19expΔ,±0.14 theor)μp. Though this value agrees with bag-model corrections to the SU(6) prediction μΔ=2μp, further clarifications on the model dependence of the result are needed, in particular since the isobar model fails to describe both the cross section and the asymmetry at the highest photon energies.
No description provided.
No description provided.
Full angular distributions of the differential cross-section dσ/dμ and of the analysing power A y in p p elastic scattering have been measured at 697 MeV/ c . The results of A y are compared with the predictions of various theoretical models.
No description provided.
No description provided.
Legendre Polynomials from fit to angular distribution (LEG(L=0)=3.59 +- 0.02).
Asymmetries A 0 n have been measured at LEAR for s¯s elastic scattering for 15 beam momenta from 497 to 1550 MeV/ c .
No description provided.
No description provided.
No description provided.
Accurate measurements of the left-right asymmetry in π−p→γn at pπ=427−625 MeV/c with a transversely polarized target are reported. Results are compared with the predictions from the Arai and Fujii single-pion photoproduction partial-wave analysis and with data on the inverse process measured with a deuterium target. The agreement is poor, casting doubt on the correctness of the value for the radiative-decay amplitude of the neutral Roper resonance now in use.
No description provided.
No description provided.
No description provided.
The asymmetry parameter A in π−p elastic scattering at incident pion laboratory kinetic energies Tπ of 98, 238, and 2922 MeV and in π−p charge-exchange scattering π−p→π0n at Tπ=238, 292, and 310 MeV have been measured over a wide range of scattering angles (typically from about 60° to 130° c.m.) with a polarized proton target. The data have been used in an energy-independent phase-shift analysis to improve the precision of the pion-nucleon phase shifts, to set new limits on violation of isospin conservation in the pion-nucleon S wave, and to confirm significant charge dependence in the P32 wave.
Axis error includes +- 0.0/0.0 contribution (?////BACKGROUND SUBTRACTION SMALL).
Axis error includes +- 0.0/0.0 contribution (?////BACKGROUND SUBTRACTION SMALL).
Axis error includes +- 0.0/0.0 contribution (?////BACKGROUND SUBTRACTION SMALL).
The polarization for the\(\bar pp\) elastic scattering was measured as a function of the centre-of-mass angle of scattering between 17° and 90° at the average incident momentum of 0.7 GeV/c by using doublescattering events in a bubble chamber. The average value of the polarization was found to be 0.23 ± 0.05. The angular dependence of the polarization obtained in this experiment was interpreted by the strong absorptive potential model for\(\bar {\mathcal{N}}{\mathcal{N}}\) interactions recently proposed.
SIGN OF POLARIZATION TAKEN AS POSITIVE ACCORDING TO THE DATA OF ALBROW ET AL., NP B37, 349 (1972).
The polarization for the K + n elastic and charge-exchange reactions was measured at the momenta of 1.06, 1.28, 1.39 and 1.49 GeV/ c . It was found to be negative for the K + n elastic process and generally positive for the charge-exchange process. The present results are compared with the predictions of phase shift analyses.
No description provided.
No description provided.
No description provided.
None
Axis error includes +- 3/3 contribution.
Axis error includes +- 3/3 contribution.
Axis error includes +- 3/3 contribution.
The polarization of the recoil neutrons from the reaction γ p→ π + n was measured at a c.m. angle of 105° for incident photon energies between 675 and 1125 MeV. A scattered π + meson and a recoil neutron were detected in coincidence with a magnetic spectrometer and a neutron polarimeter system using liquid hydrogen. Results are compared with recent phenomenological analyses and the other existing data measured by the double polarization measurement technique.
ERRORS ARE STATISTICAL ONLY.
The recoil proton polarization of proton Compton scattering (γp→γp) was measured in the photon energy range from 500 MeV to 1000 MeV atθ∗=100° and from 400MeV to 800 MeV atθ∗=130°. A recoil proton and a scattered photon were detected in coincidence with a magnetic spectrometer and a photon detector. The recoil proton polarization was measured with a carbon polarimeter. The results are compared with a phenomenological analysis based on an isobar model and a dynamical analysis based on the dispersion relation.
No description provided.
No description provided.
The polarized target asymmetry for γ n→ π − p was measured over the second resonance region from 0.55 to 0.9 GeV at pion c.m. angles between 60° and 120°. A double-arm spectrometer was used with a deuterated butanol target to detect both the pion and the proton, thus considerably improving the data quality. Including the new data in the amplitude analysis, the radiative decay widths of three resonances were determined more accurately than before. The results are compared with various quark models.
PHOTON ENERGY IS IN THE NEUTRON REST FRAME.
PHOTON ENERGY IS IN THE NEUTRON REST FRAME.
PHOTON ENERGY IS IN THE NEUTRON REST FRAME.
The first measurements are reported of the asymmetry in resonance-region scattering of longitudinally polarized electrons by longitudinally polarized protons. Data have been obtained at Q2=0.5 and 1.5 (GeV/c)2 in the missing-mass range W=1.1−1.9 GeV. Results are compatible with a multipole analysis of single-pion electroproduction. The spin-dependent behavior is consistent with a duality mechanism as in the unpolarized case.
ELECTRON ASYMMETRY AT Q**2 ABOUT 0.5 GEV**2.
ELECTRON ASYMMETRY AT Q**2 ABOUT 1.5 GEV**2.
PHOTON ASYMMETRY AT Q**2 ABOUT 0.5 GEV**2.
The recoil proton polarization of the reaction γ p → π 0 p was measured at a c.m. angle of 100° for incident photon energies between 451 and 1106 MeV, and at an angle of 130° for energies from 400 to 1142 MeV. One photon, decayed from a π 0 meson, and a recoil proton were detected in coincidence. Two kinds of polarization analyzer were employed. In the range of proton kinetic energy less than 420 MeV and higher than 346 MeV, carbon plates and liquid hydrogen were used for determining the polarization, respectively. The data given by the two polarimeter systems are in good agreement. Results are compared with recent phenomenological analyses. From the comparison between the present data and the polarized target data, the invariant amplitude A 3 can be estimated to be small.
RESULT WITH THE CARBON POLARIMETER.
RESULT WITH THE CARBON POLARIMETER.
RESULT WITH THE HYDROGEN POLARIMETER.
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