Angular distributions of recoil-proton polarization in elastic π±p scattering were measured at 523-, 572-, and 689-MeV incident pion kinetic energy. Polarization measurements were made by observing the azimuthal asymmetry in the subsequent scattering of recoil protons in large carbon-plate spark chambers. Typical strong variation of the polarization with pion scattering angle near the πp diffraction minima was observed. Since existing opinion favors a D13 resonance at 600 MeV, a phase-shift analysis was attempted in order to confirm the existence and parity of this resonance. Available πp total and differential cross sections, these polarization data, and some possible restrictive assumptions related to the 600-MeV resonance were used in the analysis. Though the polarization results aided significantly in restricting the number of acceptable phase-shift sets, still, many plausible and qualitatively different sets were found.
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Angular distributions of recoil-proton polarization in elastic π±p scattering were measured at 864-, 981-, and 1301-MeV incident pion kinetic energy. Polarization measurements were made by observing the azimuthal asymmetry in the subsequent scattering of recoil protons in large carbon-plate spark chambers. The spark chambers proved to be very suitable polarization analyzer detectors. Strong variation of the polarization with backward pion scattering angle was observed.
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We have measured the polarization of D*, the energy dependence of the polarization, and the spin-density matrix of D* in e+e− annihilation at a center-of-mass energy of 29 GeV using the Time Projection Chamber detector at the SLAC storage ring PEP. In 147 pb−1 of data we see no strong evidence for polarization, alignment, or final-state interactions in this fragmentation process.
Polarization is the factor alpha(z) in the expression d width (D*-->D pi)/domega = C(1+alpha(z)cos(theta)**2).
Spin density matrices for D* --> D0 pi+.
The polarization parameter for the reaction π−p→π0n has been measured at five incident been momenta between 1.03 and GeV/c. The results are compared with predictions of recent phase-shift analyses.
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The polarisation of prompt $\psi(2S)$ mesons is measured by performing an angular analysis of $\psi(2S)\rightarrow \mu^{+} \mu^{-}$ decays using proton-proton collision data, corresponding to an integrated luminosity of 1.0 fb$^{-1}$, collected by the LHCb detector at a centre-of-mass energy of 7 TeV. The polarisation is measured in bins of transverse momentum $p_\mathrm{T}$ and rapidity $y$ in the kinematic region $3.5<p_\mathrm{T}<15$ GeV$/c$ and $2.0<y<4.5$, and is compared to theoretical models. No significant polarisation is observed.
The measured prompt PSI(2S) polarisation parameter LAMBDA(THETA) in bins of YRAP and PT in the helicity frame.
The measured prompt PSI(2S) polarisation parameter LAMBDA(THETA PHI) in bins of YRAP and PT in the helicity frame.
The measured prompt PSI(2S) polarisation parameter LAMBDA(PHI) in bins of YRAP and PT in the helicity frame.
Results are presented from data recorded in 2009 by the PHENIX experiment at the Relativistic Heavy Ion Collider for the double-longitudinal spin asymmetry, $A_{LL}$, for $\pi^0$ and $\eta$ production in $\sqrt{s} = 200$ GeV polarized $p$$+$$p$ collisions. Comparison of the $\pi^0$ results with different theory expectations based on fits of other published data showed a preference for small positive values of gluon polarization, $\Delta G$, in the proton in the probed Bjorken $x$ range. The effect of adding the new 2009 \pz data to a recent global analysis of polarized scattering data is also shown, resulting in a best fit value $\Delta G^{[0.05,0.2]}_{\mbox{DSSV}} = 0.06^{+0.11}_{-0.15}$ in the range $0.05<x<0.2$, with the uncertainty at $\Delta \chi^2 = 9$ when considering only statistical experimental uncertainties. Shifting the PHENIX data points by their systematic uncertainty leads to a variation of the best-fit value of $\Delta G^{[0.05,0.2]}_{\mbox{DSSV}}$ between $0.02$ and $0.12$, demonstrating the need for full treatment of the experimental systematic uncertainties in future global analyses.
PI0 ASYM(LL) measurements from 2005.
PI0 ASYM(LL) measurements from 2006.
PI0 ASYM(LL) measurements from 2009.
We present experimental results on measuring a single spin asymmetry in η-meson production in the interaction of transversely polarized protons and antiprotons at p lab = 200 GeV / c with a proton target in the region 0.2 < x F < 0.7 for p ↑ p , 0.3 < x F < 0.7 for p ̄ ↑p and 0.7 < p T < 2.0 GeV / c . A comparison of single spin asymmetries in π- and η-meson production is made.
The true asymmetry for ETA production in proton-proton collisions.
The true asymmetry for ETA production in antiproton-proton collisions.
The reactions gamma p --> K+ Lambda and gamma p --> K+ Sigma0 were measured in the energy range from threshold up to a photon energy of 2.6 GeV. The data were taken with the SAPHIR detector at the electron stretcher facility, ELSA. Results on cross sections and hyperon polarizations are presented as a function of kaon production angle and photon energy. The total cross section for Lambda production rises steeply with energy close to threshold, whereas the Sigma0 cross section rises slowly to a maximum at about E_gamma = 1.45 GeV. Cross sections together with their angular decompositions into Legendre polynomials suggest contributions from resonance production for both reactions. In general, the induced polarization of Lambda has negative values in the kaon forward direction and positive values in the backward direction. The magnitude varies with energy. The polarization of Sigma0 follows a similar angular and energy dependence as that of Lambda, but with opposite sign.
Differential cross sections for the reaction GAMMA P --> K+ LAMBDA in the energy region 0.9 to 1.0 GeV.
Differential cross sections for the reaction GAMMA P --> K+ LAMBDA in the energy region 1.0 to 1.2 GeV.
Differential cross sections for the reaction GAMMA P --> K+ LAMBDA in the energy region 1.2 to 1.4 GeV.
We present the most accurate and complete data set for the analyzing power Ay(theta) in neutron-proton scattering. The experimental data were corrected for the effects of multiple scattering, both in the center detector and in the neutron detectors. The final data at En = 12.0 MeV deviate considerably from the predictions of nucleon-nucleon phase-shift analyses and potential models. The impact of the new data on the value of the charged pion-nucleon coupling constant is discussed in a model study.
The measured analysing power at 12 MeV. Errors contain statistics and systematics added in quadrature.
Angular distributions of the target symmetry for the reaction γ + p → π 0 + p have been measured at the Bonn 2.5 GeV Electron Synchrotron at pion c.m. angles between 13° and 63° and photon energies of 1.0 and 1.1 GeV. The π 0 mesons were detected by their two decay photons with total absorption lead-glass Čerenkov counters. Butanol was used as target material in a continuous flow 3 He cryostat operating at 0.5 K and 25 kG. The π 0 counting rate from free protons in the butanol target was derived from the measurements of the differential cross section on hydrogen. The data are compared with data of other laboratories and the results of two recent partial-wave analyses.
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