The reactione+p →> e+π++n at c.m. energyW=1125MeV and momentum transfer Q2=0.117GeV2/c2 has been measured. The transverse and longitudinal structure functions have been separated by varying the polarization of the virtual photon (Rosenbluth plot) with a 3 to 4% error. In addition the longitudinal-transverse interference term has been determined measuring the right-left asymmetry with an accuracy of 3%. The experimental data are compared to model calculations, and the sensitivity of the results to the axial and pion formfactors is discussed.
Angle PHI(P=4) is the angle between the scattering plane (defined by 1 and 3 particles) and the reaction plane (defined by 4 and 5 particles).
Angle PHI(P=4) is the angle between the scattering plane (defined by 1 and 3 particles) and the reaction plane (defined by 4 and 5 particles).
Angle PHI(P=4) is the angle between the scattering plane (defined by 1 and 3 particles) and the reaction plane (defined by 4 and 5 particles).
The angles at which the n-p elastic scattering neutron analyzing power A00n0 crosses zero were measured with precision at four TRIUMF energies below 300 MeV. The mean interaction energies are also measured with greater precision than in previous experiments. The results are En=175.26±0.23 MeV, θzx=98.48°±0.28°; En=203.15±0.20 MeV, θzx=91.31°±0.18°; En=217.24±0.19 MeV, θzx=87.64°±0.18°; and En=261.00±0.16 MeV, θzx=80.18°±0.19°. After correction for charge symmetry breaking effects, the energy where the averaged neutron-proton analyzing power crosses zero at θzx=90° is found to be En=206.8±0.6 MeV. © 1996 The American Physical Society.
Polarized beam and target.
Polarized beam and target.
Polarized beam and target.
A new measurement of $\Delta\sigma_T$ for polarized neutrons transmitted through a polarized proton target at 16.2 MeV has been made. A polarized neutron beam was obtained from the $^{3}\rm{H}(d,\vec n)^{4}\rm{He}$ reaction; proton polarization over 90\% was achieved in a frozen spin target of 20 cm$^3$ volume. The measurement yielded the value $\Delta\sigma_T=(-126\pm21\pm14)$ mb. The result of a simple phase shift analysis for the $^3S_1-^3D_1$ mixing parameter $\epsilon_1$ is presented and compared with the theoretical potential model predictions.
No description provided.
We analyze a sample of W + jet events collected with the Collider Detector at Fermilab (CDF) in ppbar collisions at sqrt(s) = 1.8 TeV to study ttbar production. We employ a simple kinematical variable "H", defined as the scalar sum of the transverse energies of the lepton, neutrino and jets. For events with a W boson and four or more jets, the shape of the "H" distribution deviates by 3.8 standard deviations from that expected from known backgrounds to ttbar production. However this distribution agrees well with a linear combination of background and ttbar events, the agreement being best for a top mass of 180 GeV/c^2.
A result of the study of the W + >= 4JETS data sample used in PRL 74, 2626, based on 67 pb-1 of integrated luminosity.. Different fit results due to two choices of the Q2 scale in VECBOS program (see paper).
The first measurement of incoherent η-photoproduction from the deuteron in the threshold region is reported. The experiment was carried out at the MAMI accelerator with the TAPS spectrometer. Total and differential inclusive cross sections have been obtained between 627 and 790 MeV. It is found that the reaction is completely dominated by the incoherent part. An upper limit for coherent η-photoproduction on the deuteron is deduced, which is substantially lower than the result from an earlier measurement. The incoherent cross section is reproduced in a participant-spectator approach under the assumption of an energy-independent ratio between the neutron and proton cross sections. Best agreement is found for the ratio σ n σ p ≈ 2 3 . The implications for the isospin components of the electromagnetic excitation of the S 11 (1535) resonance are discussed.
The helicity amplitudes A(1/2) = <S11|j(em)|nucleon> are measured.
The differential cross section of the charge-exchange reaction p p → n n has been measured at the CERN Low Energy Antiproton Ring (LEAR) at seven p momenta in the range 546–1287 MeV/ c . A pentanol polarized target has been used and the neutron and the antineutron have been detected in coincidence. The data cover most of the angular range.
No description provided.
No description provided.
No description provided.
We confirm the existence of the two I G ( J PC ) = 0 + (0 ++ ) resonances f 0 (1370) and f 0 (1500) reported by us in earlier analyses. The analysis presented here couples the final states π 0 π 0 π 0 , π 0 π 0 η and π 0 ηη of p p annihilation at rest. It is based on a 3 × 3 K -matrix. We find masses and widths of M = (1390±30) MeV, Γ = (380±80) MeV; and M = (1500±10) MeV, Γ = (154 ± 30) MeV, respectively. The product branching ratios for the production and decay into π 0 π 0 and ηη of the f 0 (1500) are (1.27 ± 0.33) · 10 −3 and (0.60 ± 0.17) · 10 −3 , respectively.
No description provided.
We have observed the ηπ + π − and ηπ 0 π 0 decay modes of the E meson in p p annihilation at rest into π + π − π 0 π 0 η . The mass and width of the E meson are 1409 ± 3 and 86 ± 10 MeV. The production and decay branching ratio is B( p p → Eππ)B(E → ηππ) = (3.3 ± 1.0) × 10 −3 . With a spin-parity analysis we determine that J P = 0 − . The observation of the ηπ 0 π 0 decay mode establishes that E is isoscalar ( C = +1). We find that E decays to η ( ππ ) s (where ( ππ ) s is an S-wave dipion) and πa 0 (980)(→ πη ) with a relative branching ratio of (78 ± 16) %. Using the K K π production and decay branching ratio measured earlier we determine that B[E → K K π] B[E → ηππ] = 0.61 ± 0.19 . A comparison with observations in radiative J Ψ decays suggests that E and ι η (1416) are identical.
Unobserved channels (E --> ETA 2PI0)2PI0 and (E --> ETA PI+ PI-)PI+PI- was taken into account.
The annihilation p p → Φγ has been investigated with the Crystal Barrel detector at LEAR for antiprotons stopped in liquid hydrogen. The observed branching ratio BR ( p p → Φγ = (1.7 ± 0.4) · 10 −5 is almost two orders of magnitude higher than expected from the OZI-rule. As a by-product, the branching ratios BR ( p p → K L K S ) = (9.0 ± 0.6) · 10 −4 and BR ( p p → Φπ 0 ) = (5.5 ± 0.7) · 10 −4 have been measured.
No description provided.
The total cross section for γp→ηp near threshold has been measured using the PHOENICS tagging system at the ELSA electron facility of the Physikalisches Institut der Universität Bonn. The photons are created by bremsstrahlung, and are tagged by measuring the momentum of each electron after the photon has been emitted. The recoil proton from γp→ηp is detected by the AMADEUS counter setup in coincidence with the tagging system. Data were taken with AMADEUS at 3.3° in the laboratory, where the large Jacobian increases our event rate so that we obtain the cross section from threshold (Eγ=707.2 MeV) to Eγ≃720 MeV with adequate statistics. The γp→ηp events are identified by kinematics, dE/dx, and timing information. We find that in our energy region the production cross section is consistent with S-wave production.
No description provided.
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