Data are presented from a high statistics bubble chamber experiment to K − p interactions over the c.m. energy range 1720 to 1796 MeV. Channel cross sections, differential cross sections and, where appropriate, polarisation distributions have been obtained for the final states K − p , K 0 n , π 0 Λ and π ± Σ ∓ . These data are compared with those from previously published experiments and with the predictions from the RL-IC 77 partial-wave amplitudes for each of these channels.
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EXTRAPOLATED FORWARD AND BACKWARD DIFFERENTIAL CROSS SECTIONS.
New data are presented for the reaction K − p → Λπ + π − at 11 energies between 1775 and 1957 MeV in the centre-of-mass. New values for the masses and widths of the Σ ± (1385) are given. The differential cross sections and the complete spin density matrices for the reactions K − p → π ± Σ ∓ (1385) were extracted from these data using also the information from the Λ decay. An energy-dependent partial-wave analysis has been carried out over the c.m. range 1775–2170 MeV also using data from an earlier experiment. Comparisons between the observed resonant amplitudes and SU(3) and SU(6) W ⊎ O(3) predictions have been made.
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LEGENDRE POLYNOMIAL COEFFICIENTS FOR ANGULAR DISTRIBUTION OF CROSS SECTION.
LEGENDRE POLYNOMIAL COEFFICIENTS FOR ANGULAR DISTRIBUTION OF DENSITY MATRIX ELEMENT RHO(MM=33,P=4,XYZ=SH).
Charged multiplicity and π 0 cross sections for π − p inelastic interactions at 70 GeV/ c are presented. The data were obtained from an exposure of the BEBC bubble chamber equipped with a track sensitive target (TST) to an unseparated negative beam at the CERN SPS. About 10 000 events were used for the charged multiplicity study, and about 2000 Dalitz pairs for the π 0 production analysis. A total of 12 e + e − pairs with a mass higher than the π 0 mass were found and analysed in terms of η or ω Dalitz pairs or decay pairs of vector mesons. Comparisons with data at other energies are made in terms of charged prong, π 0 cross sections, and of multiplicity parameters. The moments of longitudinal and transverse momentum distributions of the π 0 are determined and compared to the predictions of quark counting rule models.
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We present data for the single-pion production final states K 0 π − p, K − π 0 p and K − π + n from K − p interactions at 11 c.m. energies between 1775 and 1957 MeV. Using the K 0 π − p events the branching ratio (K s 0 → π + π − /K s 0 → all) has been determined to be 0.657 ± 0.011. New values have also been determined for the masses and widths of the K ∗0 (890) and the K ∗− (8990). These give a value of 1.5 ± 1.5 MeV for the electromagnetic mass splitting of the K ∗ . Differential cross sections and the spin-density matrix elements have been extracted for the reactions K − p → K ∗− p and K − p → K ∗0 n . An energy dependent partial-wave analysis of the K ∗ N channel from threshold up to 2170 MeV c.m. energy has been carried out yielding values for 17 resonant amplitudes for the expected Y ∗ 's and a new resonance, the S01(2030).
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We present extracted data for the pure I = 1 π 0 Λ (1520) channel from the reaction K − p → K − p π 0 at 11 incident momenta between 0.96 and 1.355 GeV/ c (1775 to 1960 MeV c.m. energy). A partial-wave analysis of this channel has been carried out over a broad c.m. energy range from 1710 to 2170 MeV using data at 27 momenta from this and earlier experiments. The 5 2 − Σ(1775) and built7 2 + Σ(2030) resonances are found to decay strongly to this channel. Amplitudes are also obtained for less dominant and less well-established resonances.
THESE CROSS SECTIONS ARE GIVEN IN TABLE 1B OF W. CAMERON ET AL., NP B146, 327 (1978).
LEGENDRE POLYNOMIAL COEFFICIENTS FOR ANGULAR DISTRIBUTION OF CROSS SECTION.
LEGENDRE POLYNOMIAL COEFFICIENTS FOR ANGULAR DISTRIBUTION OF DENSITY MATRIX ELEMENT RHO(MM=33,XYZ=SH).
We have observed the π+π− decay of the ρ′(1600) in the production reaction γp→ρ′p at 20 GeV. Using a calculation which takes into account the interference of the ρ′ with the ρ(770) and a Drell background, we find good evidence that this resonance is a radial excitation of the ρ(770). The background interference strongly distorts the angular distributions predicted by a purely s-channel helicity-conserving production mechanism. We measure m0=(1.55±0.07) GeV/c2 and Γ0=(0.28−0.08+0.03) GeV/c2.
SLOPE VARIATION WITH M(PI+ PI-) IN THE RANGE 0.4 TO 2.5 GEV.
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Forty-seven charm events have been observed in an exposure of the SLAC Hybrid Facility bubble chamber to a 20-GeV backward-scattered laser beam. Thirty-seven events survive all the necessary cuts imposed. Based on this number the total charm cross section is calculated to be 63−28+33 nb.
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Seventy-one events containing charmed-particle decays have been observed in an experiment using the SLAC Hybrid Facility exposed to a backward-scattered photon beam. Several improvements were made to the apparatus since the previous experiment on charm photoproduction. Results for the charmed-meson lifetimes are consistent with the published results from the previous experiment and the two data samples have been combined yielding a total sample of 136 charm events. After imposing rigorous cuts, 50 neutral, 48 charged, and 2 charged/neutral ambiguous decays remain. From these, the charmed-meson lifetimes are measured to be &=(8.6±1.3−0.3+0 .7)×10−13 sec, &=(6.1±0.9±0.3)×10 −13 sec, and their ratio &=1.4±0.3− 0.1+0.2. The total charm cross section at a photon energy of 20 GeV has been measured to be (62±8−10+15) nb. There is evidence for both DD¯X and D¯Λc+X production with σD¯Λc+X/σcharm=(71± 11±6)%.
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Cross sections are presented for the inclusive photoproduction of KS0, Λ, Λ¯, Ξ−, Ξ¯−, Σ0, and Σ*±(1385) at 20 GeV. An upper limit to Ω− production is also given. The data come from 284 000 hadronic events photoproduced in the SLAC 1-m hydrogen-bubble-chamber hybrid facility exposed to a nearly monochromatic, polarized 20-GeV backscattered photon beam. A comparison of the KS0, Λ, Λ¯, and Ξ− rates per inelastic event to π±p data show that γp rates are consistent with being higher than the π±p rates, providing evidence of an ss¯ component of the photon. The pair cross sections for KS0KS0, KS0Λ, KSoΛ¯, and ΛΛ¯ are presented. The xF distributions of the Λ, Λ¯, and Ξ− are compared to a quark-diquark fusion model, giving information on strange-baryon photoproduction mechanisms.
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The reaction γp→ρfast0pπ+π− has been studied with the linearly polarized 20-GeV monochromatic photon beam at the SLAC Hybrid Facility to test the prediction of s-channel helicity conservation in inelastic diffraction for t’<0.4 (GeV/c)2. In a sample of 1934 events from this reaction, the ρ0 decay-angular distributions and spin-density-matrix elements are consistent with s-channel helicity conservation, the π+π− mass shape displays the same skewing as seen in the reaction γp→pπ+π−, and the pπ+π− mass distribution compares well and scales according to the vector dominance model with that produced in π±p→πfast±pπ+π−.
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SPIN DENSITY MATRIX ELEMENTS FOR THE DIFFRACTIVE RHO0 MESON FROM STUDY OF THE ANGULAR DISTRIBUTIONS. CORRECTION HAS BEEN MADE FOR THE (20 +- 5) PCT NON DIFFRACTIVE BACKGROUND IN THE FINAL DATA SAMPLE, ASSUMING IT TO HAVE AN ISOTOPIC ANGULAR DISTRIBUTION.
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