The g p -> K^0 Sigma^+ reaction has been measured from threshold to Eg=1.45 GeV (W_cm=1.9 GeV) using the Crystal Ball and TAPS multiphoton spectrometers together with the photon tagging facility at the Mainz Microtron MAMI. In the present experiment, this reaction was searched for in the 3pi^0 p final state, by assuming K^0_S -> pi^0 pi^0 and Sigma^+ -> pi^0 p. The experimental results include total and differential cross sections as well as the polarization of the recoil hyperon. The new data significantly improve empirical knowledge about the g p -> K^0 Sigma^+ reaction in the measured energy range. The results are compared to previous measurements and model predictions. It is demonstrated that adding the present g p -> K^0 Sigma^+ results to existing data allowed a better description of this reaction with various models.
The differential cross section for photon energies 1125, 1175 and 1225 MeV.
The differential cross section for photon energies 1275, 1325, 1375 and 1425 MeV.
The recoil polarization of the SIGMA+ for photon energy 1125, 1175 and 1225 MeV.
High-statistics measurements of differential cross sections and recoil polarizations for the reaction $\gamma p \rightarrow K^+ \Sigma^0$ have been obtained using the CLAS detector at Jefferson Lab. We cover center-of-mass energies ($\sqrt{s}$) from 1.69 to 2.84 GeV, with an extensive coverage in the $K^+$ production angle. Independent measurements were made using the $K^{+}p\pi^{-}$($\gamma$) and $K^{+}p$($\pi^-, \gamma$) final-state topologies, and were found to exhibit good agreement. Our differential cross sections show good agreement with earlier CLAS, SAPHIR and LEPS results, while offering better statistical precision and a 300-MeV increase in $\sqrt{s}$ coverage. Above $\sqrt{s} \approx 2.5$ GeV, $t$- and $u$-channel Regge scaling behavior can be seen at forward- and backward-angles, respectively. Our recoil polarization ($P_\Sigma$) measurements represent a substantial increase in kinematic coverage and enhanced precision over previous world data. At forward angles we find that $P_\Sigma$ is of the same magnitude but opposite sign as $P_\Lambda$, in agreement with the static SU(6) quark model prediction of $P_\Sigma \approx -P_\Lambda$. This expectation is violated in some mid- and backward-angle kinematic regimes, where $P_\Sigma$ and $P_\Lambda$ are of similar magnitudes but also have the same signs. In conjunction with several other meson photoproduction results recently published by CLAS, the present data will help constrain the partial wave analyses being performed to search for missing baryon resonances.
Differential cross section as a function of COS(THETA(K+,CM)) for the centre-of mass range 1.69 to 1.7 GeV.
Differential cross section as a function of COS(THETA(K+,CM)) for the centre-of mass range 1.7 to 1.71 GeV.
Differential cross section as a function of COS(THETA(K+,CM)) for the centre-of mass range 1.71 to 1.72 GeV.
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.
The angular distributions of the unpolarised differential cross section and tensor analysing power $A_{xx}$ of the $\vec{d}d\to\alpha \eta$ reaction have been measured at an excess energy of 16.6 MeV. The ambiguities in the partial-wave description of these data are made explicit by using the invariant amplitude decomposition. This allows the magnitude of the s-wave amplitude to be extracted and compared with results published at lower energies. In this way, firmer bounds could be obtained on the scattering length of the $\eta \alpha$ system. The results do not, however, unambiguously prove the existence of a quasi-bound $\eta \alpha$ state.
Total cross section from fit to the differential angular distribution.
Differential angular distribution.
Analysing power measurements.
The differential cross section and deuteron analysing powers of the dp -> {pp}n charge-exchange reaction have been measured with the ANKE spectrometer at the COSY storage ring. Using a deuteron beam of energy 1170 MeV, data were obtained for small momentum transfers to a {pp} system with low excitation energy. A good quantitative understanding of all the measured observables is provided by the impulse approximation using known neutron-proton amplitudes. The proof of principle achieved here for the method suggests that measurements at higher energies will provide useful information in regions where the existing np database is far less reliable.
Differential cross section for the unpolarized DEUT P --> P P N reaction integrated over momentum transfer Q < 100 MeV.
Unpolarized differential cross section for the DEUT P --> P P N reaction of (P P) excitation energies < 3 MeV.
Spherical tensor analysing powers t20 and t22 for EPP 0.1 to 1.0 MeV and cos(theta) > 0.5.
Beam asymmetry and differential cross section for the reaction gamma+p->eta+p were measured from production threshold to 1500 MeV photon laboratory energy. The two dominant neutral decay modes of the eta meson, eta->2g and eta->3pi0, were analyzed. The full set of measurements is in good agreement with previously published results. Our data were compared with three models. They all fit satisfactorily the results but their respective resonance contributions are quite different. The possible photoexcitation of a narrow state N(1670) was investigated and no evidence was found.
Measured beam asymmetry at photon energy 724 MeV as a function of the ETA centre of mass angle.
Measured beam asymmetry at photon energy 761 MeV as a function of the ETA centre of mass angle.
Measured beam asymmetry at photon energy 810 MeV as a function of the ETA centre of mass angle.
Measurements of the eta meson production with a polarised proton beam in the reaction p(pol) p --> p p eta have been carried out at an excess energy of Q = 40 MeV. The dependence of the analysing power A_y on the polar angle theta^*_q of the eta meson in the center of mass system (CMS) has been studied. The data indicate the possibility of an influence of p- and d-waves to the close to threshold eta production.
Averaged value of the analyzing power and cross section as a function of the emmission angle of the ETA meson is the CM system.
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.
Interest in the production of hyperon-antihyperon pairs following antiproton-proton annihilation stems largely from attempts to understand the nature of flavor production. To date the major focus of both the experimental and the theoretical effort has been on the p¯p→Λ¯Λ reaction. In this paper, we present data on the complementary channels p¯p→Σ¯0Λ and p¯p→Λ¯Σ0. Events from the kinematically similar p¯p→Λ¯Λ reaction were obtained in parallel. The procedure to distinguish these three separate reactions is described and results for all channels are presented. These include the total and differential cross sections, hyperon polarizations, and spin correlation coefficients. Data were obtained at incident antiproton lab momenta of 1.726 and 1.771 GeV/c which correspond to excess kinetic energies in the p¯p→Λ¯Σ0+c.c. reaction of 26 and 40 MeV, respectively, above threshold. Comparisons are made to earlier work at similar excess energies in the p¯p→Λ¯Λ channel. The low-energy regime has been highlighted in this experiment to reduce the complexity in the theoretical analysis. © 1996 The American Physical Society.
No description provided.
Axis error includes +- 2.3/2.3 contribution.
Axis error includes +- 2.3/2.3 contribution.
We have measured angular distributions of differential cross sections and analyzing powers ( A y ) of the reaction p p → d π + at six incident proton energies between 1.3 and 2.4 GeV. They confirm the rapid variations at √ s = 2.65 GeV suggested by earlier experiments. Deviations from a monotonic behavior are also found in the excitation functions of the differential cross section at t = 0 or where Θ π + (c.m.) = 0°. Structures clearly appear at √ s = 2.4 and 2.65 GeV, in some coefficients of the associated Legendre function expansions of A y .
No description provided.
No description provided.
No description provided.
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