We have measured large-angle electron-positron pairs from the reaction γ +Be → Be+e + +e − in the e + e − invariant-mass region of 610 < m < 850 MeV/ c 2 . The phase of the photoproduction amplitude of the ϱ-meson at 4.1 – 6.1 GeV was found to deviate from pure imaginary by 11.8° ± 4.4° which corresponds to a ratio of the real to imaginary ϱ-nucleon amplitude of β = −0.2 ± 0.1.
No description provided.
Results are presented on effective-mass distributions, differentisl cross sections and longitudinal c.m. momentum distributions for the channels K − p → K − p π o , K o p π − and K − π + n , obtained from a sample of approximately 28 000 inelastic two-pronged interactions at 4.2 GeV/ c incident momentum. The results are in satisfactory agreement with the prediction of a generalized Veneziano-model corrected for (non-dual) π -and pomeron exchange. For the channel K − pπ o pomeron exchange contributes about 20% of the cross section. In the channel K − π + n the dual, pion and pomeron contributions are responsible for resp. 15%, 65% and 20% of the total cross section.
BREIT-WIGNER FITS.
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The real part of the forward amplitude for Compton scattering on protons was measured through the interference between the Compton and Bethe-Heithler amplitudes by detecting the zero-degree electron pairs asymmetrically. The measurement was made at an average photon energy of 〈k〉=2.2 GeV, and an average momentum transfer to the recoil proton 〈t〉=−0.027 (GeV/c)2. The result confirms the prediction of the Kramers-Kronig relation.
No description provided.
A bubble-chamber study is presented of a 10 events/μb experiment using K − mesons of 4.25 GeV/ c incident momentum. Differential and total cross sections are determined for 7 different reactions: K − p → K 0 n ( la ), → π 0 Λ ( lb ), → ηΛ ( lc ), → η′Λ ( ld ), → π − Σ ( le ), → π + Σ − ( lf ), K + Ξ − ( lg ) . The experimental characteristics in d σ /d t of each reaction are described: (la) shows a levelling off at t = 0 (GeV/ c ) 2 , a break at t = −0.6 (GeV/ c ) 2 and no backward events, (lb) d σ /d t has a smooth behaviour and a measurable backward component with an indication of a dip at u = −0.2 (GeV/ c ) 2 , (1c) d σ /d t shows a dip in the region between t ≈ −0.2 and −0.4 (GeV/ c ) 2 , (ld) d σ /d t has a smooth behaviour; neither this reaction nor the preceding one shows a clear evidence for backward events, (le) d σ /d t has a break at t = −0.5 (GeV/ c ) 2 ; there is a significant cross section in the backward region; (lf) and (lg) show mainly backward production. The polarization of the hyperon is measured in the reactions (lb), (lc), (ld) and (le) in the forward production peak. The statistics do not allow the detection of a definite structure in the polarization but the sign and magnitude are determined. An interpretation of the results is given in terms of a dual Regge model, including the effects of absorption as elaborated recently by several authors.
No description provided.
No description provided.
No description provided.
Results on the elastic K − π − scattering have been obtained from a study of the K − π − system in 15 000 events of the type K − p→K − π − p π + at a K − beam momentum of 4.25 GeV/ c . The on-mass-shell values of the spherical harmonic moments of the K − π − scattering angular distribution and the K − π − elastic cross section have been obtained by extrapolation to the pion pole. From these values we determined the s- and p-wave phase shifts δ 0 3 and δ 1 3 as a function of the effective mass of the K − π − system between threshold and 1.25 GeV/ c 2 . The value of | δ 0 3 | is smaller than 17° for all mass values and the existence of a p-wave cannot be neglected. At m K − π − = 1.18 GeV/ c 2 there are two solutions for the phase shifts. On the average, the cross section of the K − π − elastic scattering over the region of the effective mass considered amounts to approximately 2.5 mb.
The errors combine statistical and systematical effects.
The errors are statistical.
Results are presented for the quasi two-body hypercharge exchange reactions of the type using data from a high statistics bubble chamber experiment. Total and differential cross sections and the momentum transfer dependence of the meson and hyperon resonance single density matrix elements are discussed. Amplitude analyses are performed for the first two reactions. The results are compared with quark model and duality predictions and with those from other related reactions.
No description provided.
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No definite evidence for structure is found in the p¯p→n¯n cross section between 276 and 963 MeV/c. From these results limits are deduced on properties of the narrow enhancement reported in the p¯p total cross section at 475 MeV/c.
No description provided.
Data are presented from a high statistics bubble chamber experiment to study K − p interactions in the c.m. energy range 1775 to 1957 MeV. For the reactions K − p → K − p, K − p → K 0 n , K − p → Λπ 0 and K − p → Σ ± π ∓ channel cross sections, differential cross sections and, where appropriate, polarisation distributions have been obtained. The channel cross sections for K − p → Σ 0 π 0 are presented. In general the results are in agreement with those previously published although a significant discrepancy has been found in the Σ ± π ∓ cross sections at the lower energies. New measurements of the Σ ± lifetimes have also been obtained ( τ Σ − = 1.49 ± 0.03 × 10 −10 sec, τ Σ + = 0.807 ± 0.013 × 10 −10 sec).
No description provided.
THE FORWARD DIFFERENTIAL CROSS SECTION IS THE EXTRAPOLATED VALUE OF THE LEGENDRE POLYNOMIAL FIT.
No description provided.
Coherent photoproduction of vector mesons ρ0, ω, φ, and ρ′ on deuterium was studied using the SLAC 82-in. bubble chamber exposed to linearly polarized photons at 5.5 GeV. The reaction channel γd→π+π−d was studied in detail. Nine independent density-matrix parameters have been determined from the ρ0 decay distribution. ρ production in this channel was found to proceed almost completely through natural-parity exchange for |t|≤0.25 GeV2 and conserve s-channel c.m. helicity for |t|≤0.15 GeV2. A measurement of differential cross section for this channel has been made.
POLARIZED PHOTON - VECTOR MESON DENSITY MATRICES ARE EXPLAINED BY SCHILLING/SEYBOTH/WOLF NP B15, 397 (1970). 'SH' - HELICITY FRAME..............Z = 3,RF = 1-2. 'TH' - GOTTFRIED-JACKSON FRAME.....Z = 1,RF = 3. 'ADAIR' - ADAIR FRAME..............Z = 1,RF = 1-2.
No description provided.
ERROR INCLUDES BACKGROUND UNCERTAINTY.
Using a high statistics sample of K − p interactions at 4.2 GeV/ c , the production and decay properties of the Ξ ∗ (1820) are discussed. The mass and width are found to be M = (1823 ± 2) MeV and Γ = (21 ± 7) MeV. Evidence is found for Ξ ∗ (2030) in the Σ K ̄ channel and for a new Ξ ∗ at a mass of 2120 MeV in the ΛK − channel.
XI(1820)- PRODUCTION CROSS SECTIONS ARE FOR -UP < 3 GEV**2 AND ARE CORRECTED FOR ISOSPIN AND UNSEEN DECAY MODES.
No description provided.
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