A search for charm production in the coherent diffractive dissociation reaction pSi→XSi was carried out for the modes D 0 → K − π + , D 0 → K − π + π + π − , and D + → K − π + π + . No charm signals were observed, and the 90% confidence level upper limit for coherent charm pair production was determined to be 26 μ b per silicon nucleus. The results are interpreted as an upper limit of 0.2% on the amount of intrinsic charm in the proton.
90 pct CL upper limits.
We have made improved measurements of 43.8 ± 0.8, 41.3 ± 0.4 and 39.3 ± 0.8 mb for the p p elastic cross sections at 1.11, 1.33 and 1.52 GeV/ c laboratory momenta respectively. Sharp forward peaks in the differential cross sections with broad secondary maxima agree with previous observations [3–6]. The forward differential cross sections are (11 ± 3)% above the optical point in agreement with real amplitudes extended from lower momenta using dispersion relations [7]. The elastic cross sections do not show any structure in the s -channel. Backward differential cross sections show the onset of a “third diffraction peak” but no evidence for other structure in agreement with earlier experiments [6, 13].
STATISTICAL PLUS SYSTEMATIC ERRORS.
COUNTS WERE MULTIPLIED BY 1.000 TO GET THESE.. TOTAL NUMBER EVENTS= 543. READ FROM GRAPH.
COUNTS WERE MULTIPLIED BY .420 TO GET THESE.. TOTAL NUMBER EVENTS= 1099. READ FROM GRAPH.
We report results from a measurement of the inclusive diffraction dissociation of photons on hydrogen, γp→Xp, in the range 75<pγ<148 GeV/c, 0.02<‖t‖<0.1 (GeV/c)2, and MX2/s<0.1. Our data show an exponential t dependence and a dominant 1/MX2 behavior for MX2>4 GeV2. We test the finite-mass sum rule and, by comparing γp with π−p data obtained in the same apparatus, we test factorization.
EXTRACTED ELASTIC CROSS SECTIONS.
RESULTS OF EXPONENTIAL FITS TO ELASTIC CROSS SECTIONS.
DIFFERENTIAL CROSS SECTIONS FOR INELASTIC EVENTS.
Photon proton cross sections for elastic light vector meson production, σelνp, inelastic diffractive production, σndνp, non-diffractive production, σdνp, as well as the total cross section, σtotνp, have been measured at an average υp center of mass energy of 180 GeV with the ZEUS detector at HERA. The resulting values are σelνp = 18 ± 7 μb, σdνp = 33 ± 8 μb, σndνp = 91 ± 11 μb, and σtotνp 143 ± 17 μb, where the errors include statistical and systematic errors added in quadrature.
Errors contain both statistics and systematics.
An analysis of theA-dependence of the target-diffractive cross-section is presented. Data on thet-dependence of the cross section are fitted in the usual exponential form. The mean multiplicity of negative particles produced diffractively is found not to be sensitive to the nuclear mass. TheA-dependence of the emitted proton multiplicity and the angular distributions of the produced charged particles suggest re-scattering of the emitted particles on other nucleons of the nucleus. All these facts are compared with results obtained by Monte-Carlo simulation according to a two-component Dual Parton Model.
For target-diffractive cross-section.
For target-diffractive cross-section.
Multiplicities for the diffractive system.
Results on the multiplicity structure of diffractively excited meson and proton systems in À+/K+p interactions at 250 GeV/c are presented for diffractive masses up to about 9 GeV. The energy dependence of the average charge multiplicity and the shape of the multiplicity distribution in terms of KNO-scaling and negative binomial distribution are investigated. The diffractive systems are compared toe+e−,lh and non-diffractivehh final states as suggested by modern approaches of the Pomeron-hadron collision. Systematic differences are found between diffractive meson and proton systems but also between diffraction and the reactions compared to.
No description provided.
No description provided.
No description provided.
An experiment resulting in the first measurement of the isospin-mixing, charge-symmetry-violating component of the n−p interaction has been performed. The experiment determined the difference in the angles of the zero crossing of the neutron and proton analyzing powers An and Ap at 477 MeV. In terms of the laboratory scattering angle of the neutron, the measured difference is θ0n(An)−θ0n(Ap)=+0.13° ±0.06° (±0.03°), where the second error is a worst-case estimate of systematic error. The resulting difference in the analyzing powers at the zero-crossing angle is An−Ap=+0.0037 ±0.0017 (±0.0008).
No description provided.
The effect of isospin-violating, charge-symmetry-breaking (CSB) terms in the np interaction has been observed at TRIUMF by measuring the difference in the zero-crossing angles of the neutron and proton analyzing powers, An and Ap, at a neutron energy of 477 MeV. The scattering asymmetries were measured with a neutron beam incident on a polarizable proton target. To reduce systematic errors, interleaved measurements of An and Ap were made using the same beam and target (apart from their respective polarization states). Neutrons and protons were detected in coincidence in the center-of-mass angle range from 59°–80°. The difference in zero-crossing angles was 0.340°±0.162° (±0.058°), which yields ΔA≡An-Ap=0.0047±0.0022 (±0.0008) using dA/dθc.m.=−0.01382 deg−1. The second errors represent systematic effects. This result is in good agreement with recent theoretical calculations which include CSB effects due to the np mass difference in π, ρ, and 2π exchange, electromagnetic coupling of the neutron anomalous magnetic moment to the proton current, ρ-ω-meson mixing, and short- and medium-range effects of the up- and down-quark mass difference.
No description provided.
This paper reports studies of the reactions γp→ρ π π πp and γp→ρ ρ πp. In particular a peak is reported in the ρ ρ π mass spectrum with closely similar mass and width to those of the ω ρ π peak previously reported in the reaction γp→ω ρ πp. The ratio of production cross sections is found to be ρ ρ π/ω ρ π=0.96±0.19, in serious disagreement with the expectation from Vector Meson Dominance. A possible explanation is indicated.
No description provided.
Analyzing powers for πp elastic scattering at bombarding energies below the Δ(1232) resonance were measured at TRIUMF using the CHAOS spectrometer and a polarized spin target. This work presents π− data at six incident energies of 57, 67, 87, 98, 117, and 139 MeV, and a single π+ data set at 139 MeV. The higher energy measurements cover an angular range of 72°<~θc.m.<~180° while the lower energies were limited to 101°<~θc.m.<~180°. There is a high degree of consistency between this work and the predictions of the VPI/GWU group’s SM95 partial wave analysis.
Analysing power measurements for a 139 GeV PI+ beam (standard track).
Analysing power measurements for a 139 GeV PI- beam (standard track).
Analysing power measurements for a 117 GeV PI- beam (standard track).
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