359 research outputs found
The PSI np data and their effect on the charge coupling constant
Differential cross sections of elastic neutron-proton scattering have been measured for the energy range from 200 MeV to 580 MeV. The angular interval for the detection of the recoiling proton ranges up to 48 degree in the laboratory system. This corresponds to an interval of the scattering angle from 80 degree to 180 degree in the centre-of-mass system. For absolute normalization the simultaneously measured np --> d Pi^o reaction was used above 280 MeV. The charged Pi-NN coupling constant has been determined to f^2_{Pi-n-p} = 0.076+-0.001
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Reciprocal space slicing: A time-efficient approach to femtosecond x-ray diffraction
An experimental technique that allows faster assessment of out-of-plane strain dynamics of thin film heterostructures via x-ray diffraction is presented. In contrast to conventional high-speed reciprocal space-mapping setups, our approach reduces the measurement time drastically due to a fixed measurement geometry with a position-sensitive detector. This means that neither the incident (Ï) nor the exit ( 2Ξ ) diffraction angle is scanned during the strain assessment via x-ray diffraction. Shifts of diffraction peaks on the fixed x-ray area detector originate from an out-of-plane strain within the sample. Quantitative strain assessment requires the determination of a factor relating the observed shift to the change in the reciprocal lattice vector. The factor depends only on the widths of the peak along certain directions in reciprocal space, the diffraction angle of the studied reflection, and the resolution of the instrumental setup. We provide a full theoretical explanation and exemplify the concept with picosecond strain dynamics of a thin layer of NbO2
Study of the reaction pbar p -> phi phi from 1.1 to 2.0 GeV/c
A study has been performed of the reaction pbar p -> 4K using in-flight
antiprotons from 1.1 to 2.0 GeV/c incident momentum interacting with a hydrogen
jet target. The reaction is dominated by the production of a pair of phi
mesons. The pbar p -> phi phi cross section rises sharply above threshold and
then falls continuously as a function of increasing antiproton momentum. The
overall magnitude of the cross section exceeds expectations from a simple
application of the OZI rule by two orders of magnitude. In a fine scan around
the xi/f_J(2230) resonance, no structure is observed. A limit is set for the
double branching ratio B(xi -> pbar p) * B(xi -> phi phi) < 6e-5 for a spin 2
resonance of M = 2.235 GeV and Width = 15 MeV.Comment: 13 pages, 13 figures, 2 tables, Latex. To be published in Phys. Rev.
Measurement of the pbar p -> Ks Ks Reaction from 0.6 to 1.9 GeV/c
The pbar p -> Ks Ks -> 4pi+/- cross section was measured at incident
antiproton momenta between 0.6 and 1.9 GeV/c using the CERN Low Energy
Antiproton Ring (LEAR). This investigation was part of a systematic study of
in-flight antiproton-proton annihilations into two-neutral-meson final states
in a search for hadronic resonances. A coarse scan of the pbar p -> Ks Ks cross
section as a function of center-of-mass energy between 1.964 and 2.395 GeV/c^2
and a fine scan of the region surrounding the Xi(2220) are presented. Upper
limits on the product branching ratio BR(Xi -> pbar p)BR(Xi -> Ks Ks) are
determined for a wide range of mass and width assumptions based on the
non-observation of the Xi(2220). A rise in the pbar p -> Ks Ks cross section is
observed near 2.15 GeV/c^2, which is consistent with the f2(2150) resonance.Comment: 11 pages, Latex, to be published in Phys Rev D (Oct 97
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